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DrCharbonneau

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Reply with quote  #16 

M7.2 - 110km ENE of Taron, Papua New Guinea 2013-07-07 18:35:30 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

 
 
 
 

Legend

Epicenter

Nearby City

Plate Boundaries

 

GSHAP Hazard

ShakeMap

50 km
30 mi
Powered by Leaflet
3.939°S, 153.882°E
Depth: 378.8km (235.4mi)

Event Time

  1. 2013-07-07 18:35:30 UTC
  2. 2013-07-08 04:35:30 UTC+10:00 at epicenter
  3. 2013-07-07 21:35:30 UTC+03:00 system time

Location

3.939°S 153.882°E depth=378.8km (235.4mi)

Nearby Cities

  1. 110km (68mi) ENE of Taron, Papua New Guinea
  2. 185km (115mi) ENE of Kokopo, Papua New Guinea
  3. 311km (193mi) NW of Arawa, Papua New Guinea
  4. 374km (232mi) ESE of Kavieng, Papua New Guinea
  5. 904km (562mi) NW of Honiara, Solomon Islands

Tectonic Summary

Seismotectonics of the New Guinea Region and Vicinity

The Australia-Pacific plate boundary is over 4000 km long on the northern margin, from the Sunda (Java) trench in the west to the Solomon Islands in the east. The eastern section is over 2300 km long, extending west from northeast of the Australian continent and the Coral Sea until it intersects the east coast of Papua New Guinea. The boundary is dominated by the general northward subduction of the Australia plate.

Along the South Solomon trench, the Australia plate converges with the Pacific plate at a rate of approximately 95 mm/yr towards the east-northeast. Seismicity along the trench is dominantly related to subduction tectonics and large earthquakes are common: there have been 13 M7.5+ earthquakes recorded since 1900. On April 1, 2007, a M8.1 interplate megathrust earthquake occurred at the western end of the trench, generating a tsunami and killing at least 40 people. This was the third M8.1 megathrust event associated with this subduction zone in the past century; the other two occurred in 1939 and 1977.

Further east at the New Britain trench, the relative motions of several microplates surrounding the Australia-Pacific boundary, including north-south oriented seafloor spreading in the Woodlark Basin south of the Solomon Islands, maintain the general northward subduction of Australia-affiliated lithosphere beneath Pacific-affiliated lithosphere. Most of the large and great earthquakes east of New Guinea are related to this subduction; such earthquakes are particularly concentrated at the cusp of the trench south of New Ireland. 33 M7.5+ earthquakes have been recorded since 1900, including three shallow thrust fault M8.1 events in 1906, 1919, and 2007.

The western end of the Australia-Pacific plate boundary is perhaps the most complex portion of this boundary, extending 2000 km from Indonesia and the Banda Sea to eastern New Guinea. The boundary is dominantly convergent along an arc-continent collision segment spanning the width of New Guinea, but the regions near the edges of the impinging Australia continental margin also include relatively short segments of extensional, strike-slip and convergent deformation. The dominant convergence is accommodated by shortening and uplift across a 250-350 km-wide band of northern New Guinea, as well as by slow southward-verging subduction of the Pacific plate north of New Guinea at the New Guinea trench. Here, the Australia-Pacific plate relative velocity is approximately 110 mm/yr towards the northeast, leading to the 2-8 mm/yr uplift of the New Guinea Highlands.

Whereas the northern band of deformation is relatively diffuse east of the Indonesia-Papua New Guinea border, in western New Guinea there are at least two small (<100,000 km²) blocks of relatively undeformed lithosphere. The westernmost of these is the Birds Head Peninsula microplate in Indonesia's West Papua province, bounded on the south by the Seram trench. The Seram trench was originally interpreted as an extreme bend in the Sunda subduction zone, but is now thought to represent a southward-verging subduction zone between Birds Head and the Banda Sea.

There have been 22 M7.5+ earthquakes recorded in the New Guinea region since 1900. The dominant earthquake mechanisms are thrust and strike slip, associated with the arc-continent collision and the relative motions between numerous local microplates. The largest earthquake in the region was a M8.2 shallow thrust fault event in the northern Papua province of Indonesia that killed 166 people in 1996.

The western portion of the northern Australia plate boundary extends approximately 4800 km from New Guinea to Sumatra and primarily separates Australia from the Eurasia plate, including the Sunda block. This portion is dominantly convergent and includes subduction at the Sunda (Java) trench, and a young arc-continent collision.

In the east, this boundary extends from the Kai Islands to Sumba along the Timor trough, offset from the Sunda trench by 250 km south of Sumba. Contrary to earlier tectonic models in which this trough was interpreted as a subduction feature continuous with the Sunda subduction zone, it is now thought to represent a subsiding deformational feature related to the collision of the Australia plate continental margin and the volcanic arc of the Eurasia plate, initiating in the last 5-8 Myr. Before collision began, the Sunda subduction zone extended eastward to at least the Kai Islands, evidenced by the presence of a northward-dipping zone of seismicity beneath Timor Leste. A more detailed examination of the seismic zone along it's eastern segment reveals a gap in intermediate depth seismicity under Timor and seismic mechanisms that indicate an eastward propagating tear in the descending slab as the negatively buoyant oceanic lithosphere detaches from positively buoyant continental lithosphere. On the surface, GPS measurements indicate that the region around Timor is currently no longer connected to the Eurasia plate, but instead is moving at nearly the same velocity as the Australia plate, another consequence of collision.

Large earthquakes in eastern Indonesia occur frequently but interplate megathrust events related to subduction are rare; this is likely due to the disconnection of the descending oceanic slab from the continental margin. There have been 9 M7.5+ earthquakes recorded from the Kai Islands to Sumba since 1900. The largest was the great Banda Sea earthquake of 1938 (M8.5) an intermediate depth thrust faulting event that did not cause significant loss of life.

More information on regional seismicity and tectonics


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The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
DrCharbonneau

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Reply with quote  #17 

M6.6 - 29km NE of Kandrian, Papua New Guinea 2013-07-07 20:30:07 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

 
 
 
 

Legend

Epicenter

Nearby City

Plate Boundaries

 

GSHAP Hazard

ShakeMap

50 km
30 mi
Powered by Leaflet
Papua New Guinea
6.015°S, 149.722°E
Depth: 62.0km (38.5mi)

Event Time

  1. 2013-07-07 20:30:07 UTC
  2. 2013-07-08 06:30:07 UTC+10:00 at epicenter
  3. 2013-07-07 23:30:07 UTC+03:00 system time

Location

6.016°S 149.722°E depth=62.0km (38.5mi)

Nearby Cities

  1. 29km (18mi) NE of Kandrian, Papua New Guinea
  2. 69km (43mi) SW of Kimbe, Papua New Guinea
  3. 312km (194mi) ENE of Lae, Papua New Guinea
  4. 336km (209mi) WSW of Kokopo, Papua New Guinea
  5. 471km (293mi) NE of Port Moresby, Papua New Guinea

Tectonic Summary

Seismotectonics of the New Guinea Region and Vicinity

The Australia-Pacific plate boundary is over 4000 km long on the northern margin, from the Sunda (Java) trench in the west to the Solomon Islands in the east. The eastern section is over 2300 km long, extending west from northeast of the Australian continent and the Coral Sea until it intersects the east coast of Papua New Guinea. The boundary is dominated by the general northward subduction of the Australia plate.

Along the South Solomon trench, the Australia plate converges with the Pacific plate at a rate of approximately 95 mm/yr towards the east-northeast. Seismicity along the trench is dominantly related to subduction tectonics and large earthquakes are common: there have been 13 M7.5+ earthquakes recorded since 1900. On April 1, 2007, a M8.1 interplate megathrust earthquake occurred at the western end of the trench, generating a tsunami and killing at least 40 people. This was the third M8.1 megathrust event associated with this subduction zone in the past century; the other two occurred in 1939 and 1977.

Further east at the New Britain trench, the relative motions of several microplates surrounding the Australia-Pacific boundary, including north-south oriented seafloor spreading in the Woodlark Basin south of the Solomon Islands, maintain the general northward subduction of Australia-affiliated lithosphere beneath Pacific-affiliated lithosphere. Most of the large and great earthquakes east of New Guinea are related to this subduction; such earthquakes are particularly concentrated at the cusp of the trench south of New Ireland. 33 M7.5+ earthquakes have been recorded since 1900, including three shallow thrust fault M8.1 events in 1906, 1919, and 2007.

The western end of the Australia-Pacific plate boundary is perhaps the most complex portion of this boundary, extending 2000 km from Indonesia and the Banda Sea to eastern New Guinea. The boundary is dominantly convergent along an arc-continent collision segment spanning the width of New Guinea, but the regions near the edges of the impinging Australia continental margin also include relatively short segments of extensional, strike-slip and convergent deformation. The dominant convergence is accommodated by shortening and uplift across a 250-350 km-wide band of northern New Guinea, as well as by slow southward-verging subduction of the Pacific plate north of New Guinea at the New Guinea trench. Here, the Australia-Pacific plate relative velocity is approximately 110 mm/yr towards the northeast, leading to the 2-8 mm/yr uplift of the New Guinea Highlands.

Whereas the northern band of deformation is relatively diffuse east of the Indonesia-Papua New Guinea border, in western New Guinea there are at least two small (<100,000 km²) blocks of relatively undeformed lithosphere. The westernmost of these is the Birds Head Peninsula microplate in Indonesia's West Papua province, bounded on the south by the Seram trench. The Seram trench was originally interpreted as an extreme bend in the Sunda subduction zone, but is now thought to represent a southward-verging subduction zone between Birds Head and the Banda Sea.

There have been 22 M7.5+ earthquakes recorded in the New Guinea region since 1900. The dominant earthquake mechanisms are thrust and strike slip, associated with the arc-continent collision and the relative motions between numerous local microplates. The largest earthquake in the region was a M8.2 shallow thrust fault event in the northern Papua province of Indonesia that killed 166 people in 1996.

The western portion of the northern Australia plate boundary extends approximately 4800 km from New Guinea to Sumatra and primarily separates Australia from the Eurasia plate, including the Sunda block. This portion is dominantly convergent and includes subduction at the Sunda (Java) trench, and a young arc-continent collision.

In the east, this boundary extends from the Kai Islands to Sumba along the Timor trough, offset from the Sunda trench by 250 km south of Sumba. Contrary to earlier tectonic models in which this trough was interpreted as a subduction feature continuous with the Sunda subduction zone, it is now thought to represent a subsiding deformational feature related to the collision of the Australia plate continental margin and the volcanic arc of the Eurasia plate, initiating in the last 5-8 Myr. Before collision began, the Sunda subduction zone extended eastward to at least the Kai Islands, evidenced by the presence of a northward-dipping zone of seismicity beneath Timor Leste. A more detailed examination of the seismic zone along it's eastern segment reveals a gap in intermediate depth seismicity under Timor and seismic mechanisms that indicate an eastward propagating tear in the descending slab as the negatively buoyant oceanic lithosphere detaches from positively buoyant continental lithosphere. On the surface, GPS measurements indicate that the region around Timor is currently no longer connected to the Eurasia plate, but instead is moving at nearly the same velocity as the Australia plate, another consequence of collision.

Large earthquakes in eastern Indonesia occur frequently but interplate megathrust events related to subduction are rare; this is likely due to the disconnection of the descending oceanic slab from the continental margin. There have been 9 M7.5+ earthquakes recorded from the Kai Islands to Sumba since 1900. The largest was the great Banda Sea earthquake of 1938 (M8.5) an intermediate depth thrust faulting event that did not cause significant loss of life.

More information on regional seismicity and tectonics

ShakeMap

PAGER

Impact Estimates

Historic Seismicity

City Exposure List

See PAGER XML link (above).

Did You Feel It? Tell Us!

Technical

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

Summary

Preferred Location Parameters

ParameterValueUncertainty
Magnitude6.6 MwwNot Specified
Location6.016°S, 149.722°E± 13.8 km
Depth62.0 km± 6.1 km
Number of Stations Used113
Number of Phases Used114
Minimum Distance337.3 km (3.03°)
Travel Time Residual0.99 sec
Azimuthal Gap22°
Review StatusREVIEWED
Event IDusb000i8ey
See the “Contributed Solutions” for a list of all contributed location parameters.

Contributed Solutions

 

Moment Tensor

 

P-Wave Travel Times

 

Downloads

 
 

__________________
The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
DrCharbonneau

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Reply with quote  #18 
http://earthquake.usgs.gov/earthquakes/eventpage/usb000ief9#summary

M7.3 - 216km SSE of Bristol Island, South Sandwich Islands 2013-07-15 14:03:42 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

 
 
 
 

Legend

Epicenter

Nearby City

Plate Boundaries

 

GSHAP Hazard

20 km
10 mi
Powered by Leaflet
60.860°S, 25.189°W
Depth: 31.3km (19.4mi)

Event Time

  1. 2013-07-15 14:03:42 UTC
  2. 2013-07-15 12:03:42 UTC-02:00 at epicenter
  3. 2013-07-15 17:03:42 UTC+03:00 system time

Location

60.860°S 25.189°W depth=31.3km (19.5mi)

Nearby Cities

  1. 216km (134mi) SSE of Bristol Island, South Sandwich Islands
  2. 2596km (1613mi) ESE of Ushuaia, Argentina
  3. 2841km (1765mi) SE of Punta Arenas, Chile
  4. 2851km (1772mi) SE of Rio Gallegos, Argentina
  5. 2233km (1388mi) SE of Stanley, Falkland Islands

__________________
The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
DrCharbonneau

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Reply with quote  #19 
http://earthquake.usgs.gov/earthquakes/eventpage/usb000iivv#summary

M6.5 - 46km ESE of Blenheim, New Zealand 2013-07-21 05:09:31 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

 
 
 
 

Legend

Epicenter

Nearby City

Plate Boundaries

 

GSHAP Hazard

ShakeMap

30 km
20 mi
Powered by Leaflet
41.713°S, 174.443°E
Depth: 14.0km (8.7mi)

Event Time

  1. 2013-07-21 05:09:31 UTC
  2. 2013-07-21 17:09:31 UTC+12:00 at epicenter
  3. 2013-07-21 08:09:31 UTC+03:00 system time

Location

41.713°S 174.443°E depth=14.0km (8.7mi)

Nearby Cities

  1. 46km (29mi) ESE of Blenheim, New Zealand
  2. 53km (33mi) SSW of Karori, New Zealand
  3. 54km (34mi) SSW of Wellington, New Zealand
  4. 67km (42mi) SW of Lower Hutt, New Zealand
  5. 72km (45mi) SSW of Porirua, New Zealand

Tectonic Summary

The July 21, 2013 Mw 6.5 earthquake in Cook Straight, ESE of Blenheim, New Zealand, occurred as a result of oblique thrust faulting on or near the plate boundary between the Pacific and Australia plates. At the latitude of this earthquake, the Pacific plate is converging with Australia, moving westward at a rate of approximately 43 mm/yr, and is beginning a complex transition from Pacific plate subduction along the Hikurangi Trench to the north, to transform faulting along the Alpine Fault system and its associated structures to the south west. The depth and faulting mechanism of this earthquake are consistent with this tectonic transition.

The July 21 earthquake is the latest in a sequence of moderate earthquakes in the same region over the preceding two days, which began on July 18 2013 with a M 5.3 event approximately 25 km to the northwest, and continued with a M 5.8 event on July 20, just to the northeast of the July 21 earthquake. A number of smaller shocks occurred in the same area over the intervening period, and several dozen aftershocks of M<5 had been recorded by the New Zealand national network, GeoNet, within 2 hours of the mainshock. Many of these earthquakes align on an approximate NE-SW trend between the North and South Islands of New Zealand. Historically, this region has hosted several large earthquakes, including the M 7.5 1848 Marlborough event a few tens of kilometers to the northwest of the July 21 earthquake, and the M 8.2 1855 Wairarapa event, some 80 km to the northeast. 

Seismotectonics of the Eastern Margin of the Australia Plate

The eastern margin of the Australia plate is one of the most sesimically active areas of the world due to high rates of convergence between the Australia and Pacific plates. In the region of New Zealand, the 3000 km long Australia-Pacific plate boundary extends from south of Macquarie Island to the southern Kermadec Island chain. It includes an oceanic transform (the Macquarie Ridge), two oppositely verging subduction zones (Puysegur and Hikurangi), and a transpressive continental transform, the Alpine Fault through South Island, New Zealand.

Since 1900 there have been 15 M7.5+ earthquakes recorded near New Zealand. Nine of these, and the four largest, occurred along or near the Macquarie Ridge, including the 1989 M8.2 event on the ridge itself, and the 2004 M8.1 event 200 km to the west of the plate boundary, reflecting intraplate deformation. The largest recorded earthquake in New Zealand itself was the 1931 M7.8 Hawke's Bay earthquake, which killed 256 people. The last M7.5+ earthquake along the Alpine Fault was 170 years ago; studies of the faults' strain accumulation suggest that similar events are likely to occur again.

North of New Zealand, the Australia-Pacific boundary stretches east of Tonga and Fiji to 250 km south of Samoa. For 2,200 km the trench is approximately linear, and includes two segments where old (>120 Myr) Pacific oceanic lithosphere rapidly subducts westward (Kermadec and Tonga). At the northern end of the Tonga trench, the boundary curves sharply westward and changes along a 700 km-long segment from trench-normal subduction, to oblique subduction, to a left lateral transform-like structure.

Australia-Pacific convergence rates increase northward from 60 mm/yr at the southern Kermadec trench to 90 mm/yr at the northern Tonga trench; however, significant back arc extension (or equivalently, slab rollback) causes the consumption rate of subducting Pacific lithosphere to be much faster. The spreading rate in the Havre trough, west of the Kermadec trench, increases northward from 8 to 20 mm/yr. The southern tip of this spreading center is propagating into the North Island of New Zealand, rifting it apart. In the southern Lau Basin, west of the Tonga trench, the spreading rate increases northward from 60 to 90 mm/yr, and in the northern Lau Basin, multiple spreading centers result in an extension rate as high as 160 mm/yr. The overall subduction velocity of the Pacific plate is the vector sum of Australia-Pacific velocity and back arc spreading velocity: thus it increases northward along the Kermadec trench from 70 to 100 mm/yr, and along the Tonga trench from 150 to 240 mm/yr.

The Kermadec-Tonga subduction zone generates many large earthquakes on the interface between the descending Pacific and overriding Australia plates, within the two plates themselves and, less frequently, near the outer rise of the Pacific plate east of the trench. Since 1900, 40 M7.5+ earthquakes have been recorded, mostly north of 30°S. However, it is unclear whether any of the few historic M8+ events that have occurred close to the plate boundary were underthrusting events on the plate interface, or were intraplate earthquakes. On September 29, 2009, one of the largest normal fault (outer rise) earthquakes ever recorded (M8.1) occurred south of Samoa, 40 km east of the Tonga trench, generating a tsunami that killed at least 180 people.

Across the North Fiji Basin and to the west of the Vanuatu Islands, the Australia plate again subducts eastwards beneath the Pacific, at the North New Hebrides trench. At the southern end of this trench, east of the Loyalty Islands, the plate boundary curves east into an oceanic transform-like structure analogous to the one north of Tonga.

Australia-Pacific convergence rates increase northward from 80 to 90 mm/yr along the North New Hebrides trench, but the Australia plate consumption rate is increased by extension in the back arc and in the North Fiji Basin. Back arc spreading occurs at a rate of 50 mm/yr along most of the subduction zone, except near ~15°S, where the D'Entrecasteaux ridge intersects the trench and causes localized compression of 50 mm/yr in the back arc. Therefore, the Australia plate subduction velocity ranges from 120 mm/yr at the southern end of the North New Hebrides trench, to 40 mm/yr at the D'Entrecasteaux ridge-trench intersection, to 170 mm/yr at the northern end of the trench.

Large earthquakes are common along the North New Hebrides trench and have mechanisms associated with subduction tectonics, though occasional strike slip earthquakes occur near the subduction of the D'Entrecasteaux ridge. Within the subduction zone 34 M7.5+ earthquakes have been recorded since 1900. On October 7, 2009, a large interplate thrust fault earthquake (M7.6) in the northern North New Hebrides subduction zone was followed 15 minutes later by an even larger interplate event (M7.8) 60 km to the north. It is likely that the first event triggered the second of the so-called earthquake "doublet".

More information on regional seismicity and tectonics


__________________
The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
DrCharbonneau

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Reply with quote  #20 
http://earthquake.usgs.gov/earthquakes/eventpage/usc000iq6f#summary

M6.2 - 203km NE of Bristol Island, South Sandwich Islands 2013-07-26 21:32:59 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

 
 
 
 

Legend

Epicenter

Nearby City

Plate Boundaries

 

GSHAP Hazard

ShakeMap

30 km
20 mi
Powered by Leaflet
57.789°S, 23.959°W
Depth: 10.0km (6.2mi)

Event Time

  1. 2013-07-26 21:32:59 UTC
  2. 2013-07-26 19:32:59 UTC-02:00 at epicenter
  3. 2013-07-27 00:32:59 UTC+03:00 system time

Location

57.789°S 23.959°W depth=10.0km (6.2mi)

Nearby Cities

  1. 203km (126mi) NE of Bristol Island, South Sandwich Islands
  2. 2715km (1687mi) ESE of Ushuaia, Argentina
  3. 2937km (1825mi) ESE of Rio Gallegos, Argentina
  4. 2952km (1834mi) ESE of Punta Arenas, Chile
  5. 2258km (1403mi) ESE of Stanley, Falkland Islands

ShakeMap

PAGER

Impact Estimates

City Exposure List

See PAGER XML link (above).

Did You Feel It? Tell Us!

Scientific

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

Summary

Preferred Location Parameters

ParameterValueUncertainty
Magnitude6.2 Mwp± 0.05
Location57.789°S, 23.959°W± 18.4 km
Depth10.0 km± 2.8 km
Number of Stations Used65
Number of Phases Used65
Minimum Distance873.9 km (7.85°)
Travel Time Residual1.35 sec
Azimuthal Gap85°
Review StatusMANUAL
Event IDusc000iq6f
See the “Contributed Solutions” for a list of all contributed location parameters.

Contributed Solutions

 

Moment Tensor

 

Downloads

 
 

__________________
The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
DrCharbonneau

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Posts: 501
Reply with quote  #21 
http://earthquake.usgs.gov/earthquakes/eventpage/usb000iwjv#summary


M5.7 - 84km S of Lakatoro, Vanuatu 2013-08-06 17:21:55 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

 
 
 
 

Legend

Epicenter

Nearby City

Plate Boundaries

 

GSHAP Hazard

ShakeMap

50 km
30 mi
Powered by Leaflet
16.879°S, 167.379°E
Depth: 13.9km (8.6mi)

Event Time

  1. 2013-08-06 17:21:55 UTC
  2. 2013-08-07 04:21:55 UTC+11:00 at epicenter
  3. 2013-08-06 20:21:55 UTC+03:00 system time

Location

16.879°S 167.379°E depth=13.9km (8.7mi)

Nearby Cities

  1. 84km (52mi) S of Lakatoro, Vanuatu
  2. 137km (85mi) NW of Port-Vila, Vanuatu
  3. 150km (93mi) S of Luganville, Vanuatu
  4. 447km (278mi) N of We, New Caledonia
  5. 591km (367mi) N of Dumbea, New Caledonia

Tectonic Summary

Seismotectonics of the Eastern Margin of the Australia Plate

The eastern margin of the Australia plate is one of the most sesimically active areas of the world due to high rates of convergence between the Australia and Pacific plates. In the region of New Zealand, the 3000 km long Australia-Pacific plate boundary extends from south of Macquarie Island to the southern Kermadec Island chain. It includes an oceanic transform (the Macquarie Ridge), two oppositely verging subduction zones (Puysegur and Hikurangi), and a transpressive continental transform, the Alpine Fault through South Island, New Zealand.

Since 1900 there have been 15 M7.5+ earthquakes recorded near New Zealand. Nine of these, and the four largest, occurred along or near the Macquarie Ridge, including the 1989 M8.2 event on the ridge itself, and the 2004 M8.1 event 200 km to the west of the plate boundary, reflecting intraplate deformation. The largest recorded earthquake in New Zealand itself was the 1931 M7.8 Hawke's Bay earthquake, which killed 256 people. The last M7.5+ earthquake along the Alpine Fault was 170 years ago; studies of the faults' strain accumulation suggest that similar events are likely to occur again.

North of New Zealand, the Australia-Pacific boundary stretches east of Tonga and Fiji to 250 km south of Samoa. For 2,200 km the trench is approximately linear, and includes two segments where old (>120 Myr) Pacific oceanic lithosphere rapidly subducts westward (Kermadec and Tonga). At the northern end of the Tonga trench, the boundary curves sharply westward and changes along a 700 km-long segment from trench-normal subduction, to oblique subduction, to a left lateral transform-like structure.

Australia-Pacific convergence rates increase northward from 60 mm/yr at the southern Kermadec trench to 90 mm/yr at the northern Tonga trench; however, significant back arc extension (or equivalently, slab rollback) causes the consumption rate of subducting Pacific lithosphere to be much faster. The spreading rate in the Havre trough, west of the Kermadec trench, increases northward from 8 to 20 mm/yr. The southern tip of this spreading center is propagating into the North Island of New Zealand, rifting it apart. In the southern Lau Basin, west of the Tonga trench, the spreading rate increases northward from 60 to 90 mm/yr, and in the northern Lau Basin, multiple spreading centers result in an extension rate as high as 160 mm/yr. The overall subduction velocity of the Pacific plate is the vector sum of Australia-Pacific velocity and back arc spreading velocity: thus it increases northward along the Kermadec trench from 70 to 100 mm/yr, and along the Tonga trench from 150 to 240 mm/yr.

The Kermadec-Tonga subduction zone generates many large earthquakes on the interface between the descending Pacific and overriding Australia plates, within the two plates themselves and, less frequently, near the outer rise of the Pacific plate east of the trench. Since 1900, 40 M7.5+ earthquakes have been recorded, mostly north of 30°S. However, it is unclear whether any of the few historic M8+ events that have occurred close to the plate boundary were underthrusting events on the plate interface, or were intraplate earthquakes. On September 29, 2009, one of the largest normal fault (outer rise) earthquakes ever recorded (M8.1) occurred south of Samoa, 40 km east of the Tonga trench, generating a tsunami that killed at least 180 people.

Across the North Fiji Basin and to the west of the Vanuatu Islands, the Australia plate again subducts eastwards beneath the Pacific, at the North New Hebrides trench. At the southern end of this trench, east of the Loyalty Islands, the plate boundary curves east into an oceanic transform-like structure analogous to the one north of Tonga.

Australia-Pacific convergence rates increase northward from 80 to 90 mm/yr along the North New Hebrides trench, but the Australia plate consumption rate is increased by extension in the back arc and in the North Fiji Basin. Back arc spreading occurs at a rate of 50 mm/yr along most of the subduction zone, except near ~15°S, where the D'Entrecasteaux ridge intersects the trench and causes localized compression of 50 mm/yr in the back arc. Therefore, the Australia plate subduction velocity ranges from 120 mm/yr at the southern end of the North New Hebrides trench, to 40 mm/yr at the D'Entrecasteaux ridge-trench intersection, to 170 mm/yr at the northern end of the trench.

Large earthquakes are common along the North New Hebrides trench and have mechanisms associated with subduction tectonics, though occasional strike slip earthquakes occur near the subduction of the D'Entrecasteaux ridge. Within the subduction zone 34 M7.5+ earthquakes have been recorded since 1900. On October 7, 2009, a large interplate thrust fault earthquake (M7.6) in the northern North New Hebrides subduction zone was followed 15 minutes later by an even larger interplate event (M7.8) 60 km to the north. It is likely that the first event triggered the second of the so-called earthquake "doublet".

More information on regional seismicity and tectonics

ShakeMap

PAGER

Impact Estimates

Historic Seismicity

City Exposure List

See PAGER XML link (above).

Did You Feel It? Tell Us!

Scientific

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

Summary

Preferred Location Parameters

ParameterValueUncertainty
Magnitude5.7 MwwNot Specified
Location16.879°S, 167.379°E± 13.3 km
Depth13.9 km± 5.3 km
Number of Stations Used166
Number of Phases Used168
Minimum Distance514.3 km (4.62°)
Travel Time Residual1.11 sec
Azimuthal Gap48°
Review StatusMANUAL
Event IDusb000iwjv
See the “Contributed Solutions” for a list of all contributed location parameters.

Contributed Solutions

 

Moment Tensor

 

P-Wave Travel Times

 

Downloads

 
 

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The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
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Reply with quote  #22 
http://earthquake.usgs.gov/earthquakes/eventpage/usb000j275#summary


M6.6 - 99km WSW of Mutis, Colombia 2013-08-13 15:43:14 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

 
 
 
 

Legend

Epicenter

Nearby City

Plate Boundaries

 

GSHAP Hazard

ShakeMap

50 km
30 mi
Powered by Leaflet
5.871°N, 78.235°W
Depth: 10.0km (6.2mi)

Event Time

  1. 2013-08-13 15:43:14 UTC
  2. 2013-08-13 10:43:14 UTC-05:00 at epicenter
  3. 2013-08-13 18:43:14 UTC+03:00 system time

Location

5.871°N 78.235°W depth=10.0km (6.2mi)

Nearby Cities

  1. 99km (62mi) WSW of Mutis, Colombia
  2. 175km (109mi) W of Quibdo, Colombia
  3. 188km (117mi) WNW of Istmina, Colombia
  4. 196km (122mi) WNW of Tado, Colombia
  5. 373km (232mi) SSE of Panama, Panama

Tectonic Summary

Seismotectonics of the Caribbean Region and Vicinity

Extensive diversity and complexity of tectonic regimes characterizes the perimeter of the Caribbean plate, involving no fewer than four major plates (North America, South America, Nazca, and Cocos). Inclined zones of deep earthquakes (Wadati-Benioff zones), ocean trenches, and arcs of volcanoes clearly indicate subduction of oceanic lithosphere along the Central American and Atlantic Ocean margins of the Caribbean plate, while crustal seismicity in Guatemala, northern Venezuela, and the Cayman Ridge and Cayman Trench indicate transform fault and pull-apart basin tectonics.

Along the northern margin of the Caribbean plate, the North America plate moves westwards with respect to the Caribbean plate at a velocity of approximately 20 mm/yr. Motion is accommodated along several major transform faults that extend eastward from Isla de Roatan to Haiti, including the Swan Island Fault and the Oriente Fault. These faults represent the southern and northern boundaries of the Cayman Trench. Further east, from the Dominican Republic to the Island of Barbuda, relative motion between the North America plate and the Caribbean plate becomes increasingly complex and is partially accommodated by nearly arc-parallel subduction of the North America plate beneath the Caribbean plate. This results in the formation of the deep Puerto Rico Trench and a zone of intermediate focus earthquakes (70-300 km depth) within the subducted slab. Although the Puerto Rico subduction zone is thought to be capable of generating a megathrust earthquake, there have been no such events in the past century. The last probable interplate (thrust fault) event here occurred on May 2, 1787 and was widely felt throughout the island with documented destruction across the entire northern coast, including Arecibo and San Juan. Since 1900, the two largest earthquakes to occur in this region were the August 4, 1946 M8.0 Samana earthquake in northeastern Hispaniola and the July 29, 1943 M7.6 Mona Passage earthquake, both of which were shallow thrust fault earthquakes. A significant portion of the motion between the North America plate and the Caribbean plate in this region is accommodated by a series of left-lateral strike-slip faults that bisect the island of Hispaniola, notably the Septentrional Fault in the north and the Enriquillo-Plantain Garden Fault in the south. Activity adjacent to the Enriquillo-Plantain Garden Fault system is best documented by the devastating January 12, 2010 M7.0 Haiti strike-slip earthquake, its associated aftershocks and a comparable earthquake in 1770.

Moving east and south, the plate boundary curves around Puerto Rico and the northern Lesser Antilles where the plate motion vector of the Caribbean plate relative to the North and South America plates is less oblique, resulting in active island-arc tectonics. Here, the North and South America plates subduct towards the west beneath the Caribbean plate along the Lesser Antilles Trench at rates of approximately 20 mm/yr. As a result of this subduction, there exists both intermediate focus earthquakes within the subducted plates and a chain of active volcanoes along the island arc. Although the Lesser Antilles is considered one of the most seismically active regions in the Caribbean, few of these events have been greater than M7.0 over the past century. The island of Guadeloupe was the site of one of the largest megathrust earthquakes to occur in this region on February 8, 1843, with a suggested magnitude greater than 8.0. The largest recent intermediate-depth earthquake to occur along the Lesser Antilles arc was the November 29, 2007 M7.4 Martinique earthquake northwest of Fort-De-France.

The southern Caribbean plate boundary with the South America plate strikes east-west across Trinidad and western Venezuela at a relative rate of approximately 20 mm/yr. This boundary is characterized by major transform faults, including the Central Range Fault and the Boconó-San Sebastian-El Pilar Faults, and shallow seismicity. Since 1900, the largest earthquakes to occur in this region were the October 29, 1900 M7.7 Caracas earthquake, and the July 29, 1967 M6.5 earthquake near this same region. Further to the west, a broad zone of compressive deformation trends southwestward across western Venezuela and central Columbia. The plate boundary is not well defined across northwestern South America, but deformation transitions from being dominated by Caribbean/South America convergence in the east to Nazca/South America convergence in the west. The transition zone between subduction on the eastern and western margins of the Caribbean plate is characterized by diffuse seismicity involving low- to intermediate-magnitude (M<6.0) earthquakes of shallow to intermediate depth.

The plate boundary offshore of Colombia is also characterized by convergence, where the Nazca plate subducts beneath South America towards the east at a rate of approximately 65 mm/yr. The January 31, 1906 M8.5 earthquake occurred on the shallowly dipping megathrust interface of this plate boundary segment. Along the western coast of Central America, the Cocos plate subducts towards the east beneath the Caribbean plate at the Middle America Trench. Convergence rates vary between 72-81 mm/yr, decreasing towards the north. This subduction results in relatively high rates of seismicity and a chain of numerous active volcanoes; intermediate-focus earthquakes occur within the subducted Cocos plate to depths of nearly 300 km. Since 1900, there have been many moderately sized intermediate-depth earthquakes in this region, including the September 7, 1915 M7.4 El Salvador and the October 5, 1950 M7.8 Costa Rica events.

The boundary between the Cocos and Nazca plates is characterized by a series of north-south trending transform faults and east-west trending spreading centers. The largest and most seismically active of these transform boundaries is the Panama Fracture Zone. The Panama Fracture Zone terminates in the south at the Galapagos rift zone and in the north at the Middle America trench, where it forms part of the Cocos-Nazca-Caribbean triple junction. Earthquakes along the Panama Fracture Zone are generally shallow, low- to intermediate in magnitude (M<7.2) and are characteristically right-lateral strike-slip faulting earthquakes. Since 1900, the largest earthquake to occur along the Panama Fracture Zone was the July 26, 1962 M7.2 earthquake.

References for the Panama Fracture Zone:
Molnar, P., and Sykes, L. R., 1969, Tectonics of the Caribbean and Middle America Regions from Focal Mechanisms and Seismicity: Geological Society of America Bulletin, v. 80, p. 1639-1684.

More information on regional seismicity and tectonics

Additional Commentary


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The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
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Reply with quote  #23 
http://earthquake.usgs.gov/earthquakes/eventpage/usb000j4iz#summary


M6.5 - 29km SSE of Blenheim, New Zealand 2013-08-16 02:31:07 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

 
 
 
 

Legend

Epicenter

Nearby City

Plate Boundaries

 

GSHAP Hazard

ShakeMap

30 km
20 mi
Powered by Leaflet
New Zealand
41.767°S, 174.061°E
Depth: 10.0km (6.2mi)

Event Time

  1. 2013-08-16 02:31:07 UTC
  2. 2013-08-16 14:31:07 UTC+12:00 at epicenter
  3. 2013-08-16 05:31:07 UTC+03:00 system time

Location

41.767°S 174.061°E depth=10.0km (6.2mi)

Nearby Cities

  1. 29km (18mi) SSE of Blenheim, New Zealand
  2. 77km (48mi) SW of Karori, New Zealand
  3. 80km (50mi) SW of Wellington, New Zealand
  4. 84km (52mi) SE of Nelson, New Zealand
  5. 87km (54mi) ESE of Richmond, New Zealand

Tectonic Summary

The M 6.5 August 16, 2013 earthquake south of Blenheim, New Zealand, occurred as the result of strike-slip faulting on or near the plate boundary between the Pacific and Australia plates. At the latitude of this event, the Pacific plate moves towards the WSW with respect to Australia at a rate of approximately 41 mm/yr. Preliminary faulting mechanisms for the earthquake suggest it is related to either NE-SW right-lateral strike-slip motion (consistent with plate boundary oriented deformation), or NW-SE left-lateral strike-slip motion.

This region of New Zealand has hosted a number of small-moderate sized earthquakes in recent weeks, including a M 6.5 earthquake approximately 40 km east of the August 16 event in the Cook Straight, on July 21, 2013. The July 21 event was preceded by several M 5.3-5.8 events and was followed by a dozen or more aftershocks between M 4.5-5.0, delineating shallow upper plate structures aligned NE-SW, and some deeper subduction-related activity, mostly offshore of the north coast of New Zealand’s South Island.

In contrast to the earlier events, the August 16 earthquake is on land, near the eastern end of the complex Marlborough Fault System. The event is located approximately 10 km southeast of the Awatere Fault in the vicinity of Lake Grassmere. The Marlborough Fault system is characterized by a series of NE striking right-lateral strike slip faults that have dismembered the northern South Island into a series of crustal blocks that are being transported to the northeast. Although there is no specific mapped surface fault that can be linked to the August 16 event at this time, the NE trending fault plane is similarly oriented to the Awatere and Clarence faults of the Marlborough system. In 1966 a M 5.8 earthquake (interpreted to have occurred offshore to the NE of the August 16 event) was widely felt in this area, causing surface deformation of the main railroad line in the region. That event is interpreted to have occurred on a blind structure sub-parallel to the Awatere fault to its northeast.


Seismotectonics of the Eastern Margin of the Australia Plate

The eastern margin of the Australia plate is one of the most sesimically active areas of the world due to high rates of convergence between the Australia and Pacific plates. In the region of New Zealand, the 3000 km long Australia-Pacific plate boundary extends from south of Macquarie Island to the southern Kermadec Island chain. It includes an oceanic transform (the Macquarie Ridge), two oppositely verging subduction zones (Puysegur and Hikurangi), and a transpressive continental transform, the Alpine Fault through South Island, New Zealand.

Since 1900 there have been 15 M7.5+ earthquakes recorded near New Zealand. Nine of these, and the four largest, occurred along or near the Macquarie Ridge, including the 1989 M8.2 event on the ridge itself, and the 2004 M8.1 event 200 km to the west of the plate boundary, reflecting intraplate deformation. The largest recorded earthquake in New Zealand itself was the 1931 M7.8 Hawke's Bay earthquake, which killed 256 people. The last M7.5+ earthquake along the Alpine Fault was 170 years ago; studies of the faults' strain accumulation suggest that similar events are likely to occur again.

North of New Zealand, the Australia-Pacific boundary stretches east of Tonga and Fiji to 250 km south of Samoa. For 2,200 km the trench is approximately linear, and includes two segments where old (>120 Myr) Pacific oceanic lithosphere rapidly subducts westward (Kermadec and Tonga). At the northern end of the Tonga trench, the boundary curves sharply westward and changes along a 700 km-long segment from trench-normal subduction, to oblique subduction, to a left lateral transform-like structure.

Australia-Pacific convergence rates increase northward from 60 mm/yr at the southern Kermadec trench to 90 mm/yr at the northern Tonga trench; however, significant back arc extension (or equivalently, slab rollback) causes the consumption rate of subducting Pacific lithosphere to be much faster. The spreading rate in the Havre trough, west of the Kermadec trench, increases northward from 8 to 20 mm/yr. The southern tip of this spreading center is propagating into the North Island of New Zealand, rifting it apart. In the southern Lau Basin, west of the Tonga trench, the spreading rate increases northward from 60 to 90 mm/yr, and in the northern Lau Basin, multiple spreading centers result in an extension rate as high as 160 mm/yr. The overall subduction velocity of the Pacific plate is the vector sum of Australia-Pacific velocity and back arc spreading velocity: thus it increases northward along the Kermadec trench from 70 to 100 mm/yr, and along the Tonga trench from 150 to 240 mm/yr.

The Kermadec-Tonga subduction zone generates many large earthquakes on the interface between the descending Pacific and overriding Australia plates, within the two plates themselves and, less frequently, near the outer rise of the Pacific plate east of the trench. Since 1900, 40 M7.5+ earthquakes have been recorded, mostly north of 30°S. However, it is unclear whether any of the few historic M8+ events that have occurred close to the plate boundary were underthrusting events on the plate interface, or were intraplate earthquakes. On September 29, 2009, one of the largest normal fault (outer rise) earthquakes ever recorded (M8.1) occurred south of Samoa, 40 km east of the Tonga trench, generating a tsunami that killed at least 180 people.

Across the North Fiji Basin and to the west of the Vanuatu Islands, the Australia plate again subducts eastwards beneath the Pacific, at the North New Hebrides trench. At the southern end of this trench, east of the Loyalty Islands, the plate boundary curves east into an oceanic transform-like structure analogous to the one north of Tonga.

Australia-Pacific convergence rates increase northward from 80 to 90 mm/yr along the North New Hebrides trench, but the Australia plate consumption rate is increased by extension in the back arc and in the North Fiji Basin. Back arc spreading occurs at a rate of 50 mm/yr along most of the subduction zone, except near ~15°S, where the D'Entrecasteaux ridge intersects the trench and causes localized compression of 50 mm/yr in the back arc. Therefore, the Australia plate subduction velocity ranges from 120 mm/yr at the southern end of the North New Hebrides trench, to 40 mm/yr at the D'Entrecasteaux ridge-trench intersection, to 170 mm/yr at the northern end of the trench.

Large earthquakes are common along the North New Hebrides trench and have mechanisms associated with subduction tectonics, though occasional strike slip earthquakes occur near the subduction of the D'Entrecasteaux ridge. Within the subduction zone 34 M7.5+ earthquakes have been recorded since 1900. On October 7, 2009, a large interplate thrust fault earthquake (M7.6) in the northern North New Hebrides subduction zone was followed 15 minutes later by an even larger interplate event (M7.8) 60 km to the north. It is likely that the first event triggered the second of the so-called earthquake "doublet".

More information on regional seismicity and tectonics


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The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
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M6.1 - Southwest Indian Ridge 2013-08-17 16:32:31 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

 
 
 
 

Legend

Epicenter

Nearby City

Plate Boundaries

 

GSHAP Hazard

ShakeMap

50 km
30 mi
Powered by Leaflet
34.884°S, 54.067°E
Depth: 10.0km (6.2mi)

Event Time

  1. 2013-08-17 16:32:31 UTC
  2. 2013-08-17 20:32:31 UTC+04:00 at epicenter
  3. 2013-08-17 19:32:31 UTC+03:00 system time

Location

34.884°S 54.067°E depth=10.0km (6.2mi)

Nearby Cities

  1. 1286km (799mi) SSE of Fort Dauphin, Madagascar
  2. 1318km (819mi) SSE of Amboasary, Madagascar
  3. 1323km (822mi) SSE of Ambovombe, Madagascar
  4. 1345km (836mi) SE of Tsiombe, Madagascar
  5. 1557km (967mi) S of Saint-Denis, Reunion

ShakeMap

PAGER

Impact Estimates

City Exposure List

See PAGER XML link (above).

Did You Feel It? Tell Us!

Scientific

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

Summary

Preferred Location Parameters

ParameterValueUncertainty
Magnitude6.1 MwbNot Specified
Location34.884°S, 54.067°E± 16.2 km
Depth10.0 km± 2.8 km
Number of Stations Used51
Number of Phases Used51
Minimum Distance1652.0 km (14.84°)
Travel Time Residual0.94 sec
Azimuthal Gap31°
Review StatusMANUAL
Event IDusb000j5ki
See the “Contributed Solutions” for a list of all contributed location parameters.

Contributed Solutions

 

Moment Tensor

 

P-Wave Travel Times

 

Downloads

 

__________________
The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
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Reply with quote  #25 
http://earthquake.usgs.gov/earthquakes/eventpage/usb000jdt7#summary

M7.0 - 94km ESE of Adak, Alaska 2013-08-30 16:25:02 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

[C00000003][C00000003][C00000002][C00000004][C00000002][C00000004]
[C00000003][C00000003][C00000002][C00000004][C00000002][C00000004]
[image]
 
[star]
 
 
USGS Topography Open Street Map Open Aerial Map
 
USGS Faults USGS Plate Boundaries U.S. Hazard ShakeMap Nearby Cities Earthquake Location

Legend

Epicenter

Nearby City

Faults

 

Plate Boundaries

 

GSHAP Hazard

[gshap]

US Hazard

[ushazard]

ShakeMap

[mmi]
30 km
20 mi
Powered by Leaflet
51.610°N, 175.361°W
Depth: 33.5km (20.8mi)

Event Time

  1. 2013-08-30 16:25:02 UTC
  2. 2013-08-30 04:25:02 UTC-12:00 at epicenter
  3. 2013-08-30 19:25:02 UTC+03:00 system time

Location

51.610°N 175.361°W depth=33.5km (20.8mi)

Nearby Cities

  1. 94km (58mi) ESE of Adak, Alaska
  2. 1520km (944mi) SSE of Anadyr', Russia
  3. 1769km (1099mi) E of Petropavlovsk-Kamchatskiy, Russia
  4. 1785km (1109mi) E of Yelizovo, Russia
  5. 2649km (1646mi) W of Whitehorse, Canada

Tectonic Summary

The August 30, 2013 M 7.0 earthquake southeast of Adak, Alaska, occurred as the result of thrust faulting on or near the subduction zone interface between the Pacific and North America plates. At the location of this event, the Pacific plate moves towards the northwest with respect to North America at a rate of approximately 73 mm/yr, beginning its descent into the mantle at the Aleutian trench approximately 130 km south of the August 30 earthquake. The depth and mechanism of this earthquake are consistent with it occurring along the megathrust interface between these two plates.

The Aleutians Arc is familiar with large earthquakes –two-dozen events of M 6.5 or larger have occurred over the last century within 250 km of the August 30 earthquake. The largest of these was an Mw 8.6 earthquake in March of 1957, whose hypocenter was located just 15 km south of the August 30 earthquake. Aftershocks associated with the 1957 event extended for more than 1000 km along the arc, roughly from the International Dateline in the west to Unimak Island in the east. The 1957 earthquake also resulted in a large tsunami that was observed throughout the Pacific Basin, and caused damage locally along the Aleutian Arc and in Hawaii. Other large nearby events include the May 1986 Mw 8.0 earthquake 40 km to the southeast, and the June 1996 Mw 7.9 earthquake 150 km to the west. Neither of these more recent events are known to have caused fatalities or significant damage.

Seismotectonics of Alaska

The Aleutian arc extends approximately 3,000 km from the Gulf of Alaska in the east to the Kamchatka Peninsula in the west. It marks the region where the Pacific plate subducts into the mantle beneath the North America plate. This subduction is responsible for the generation of the Aleutian Islands and the deep offshore Aleutian Trench.

The curvature of the arc results in a westward transition of relative plate motion from trench-normal (i.e., compressional) in the east to trench-parallel (i.e., translational) in the west, accompanied by westward variations in seismic activity, volcanism, and overriding plate composition. The Aleutian arc is generally divided into three regions: the western, central, and eastern Aleutians. Relative to a fixed North America plate, the Pacific plate is moving northwest at a rate that increases from roughly 60 mm/yr at the arc's eastern edge to 76 mm/yr near its western terminus. The eastern Aleutian arc extends from the Alaskan Peninsula in the east to the Fox Islands in the west. Motion along this section of the arc is characterized by arc-perpendicular convergence and Pacific plate subduction beneath thick continental lithosphere. This region exhibits intense volcanic activity and has a history of megathrust earthquakes.

The central Aleutian arc extends from the Andreanof Islands in the east to the Rat Islands in the west. Here, motion is characterized by westward-increasing oblique convergence and Pacific plate subduction beneath thin oceanic lithosphere. Along this portion of the arc, the Wadati-Benioff zone is well defined to depths of approximately 200 km. Despite the obliquity of convergence, active volcanism and megathrust earthquakes are also present along this margin.

The western Aleutians, stretching from the western end of the Rat Islands in the east to the Commander Islands, Russia, in the west, is tectonically different from the central and eastern portions of the arc. The increasing component of transform motion between the Pacific and North America plates is evidenced by diminishing active volcanism; the last active volcano is located on Buldir Island, in the far western portion of the Rat Island chain. Additionally, this portion of the subduction zone has not hosted large earthquakes or megathrust events in recorded history. Instead, the largest earthquakes in this region are generally shallow, predominantly strike-slip events with magnitudes between M5-6. Deeper earthquakes do occur, albeit rather scarcely and with small magnitudes (M<4), down to approximately 50 km.

Most of the seismicity along the Aleutian arc results from thrust faulting that occurs along the interface between the Pacific and North America plates, extending from near the base of the trench to depths of 40 to 60 km. Slip along this interface is responsible for generating devastating earthquakes. Deformation also occurs within the subducting slab in the form of intermediate-depth earthquakes that can reach depths of 250 km. Normal faulting events occur in the outer rise region of the Aleutian arc resulting from the bending of the oceanic Pacific plate as it enters the Aleutian trench. Additionally, deformation of the overriding North America plate generates shallow crustal earthquakes.

The Aleutian arc is a seismically active region, evidenced by the many moderate to large earthquakes occurring each year. Since 1900, this region has hosted twelve large earthquakes (M>7.5) including the May 7, 1986 M8.0 Andreanof Islands, the June 10, 1996 M7.9 Andreanof Islands, and the November 17, 2003 M7.8 Rat Islands earthquakes. Six of these great earthquakes (M8.3 or larger) have occurred along the Aleutian arc that together have ruptured almost the entire shallow megathrust contact. The first of these major earthquakes occurred on August 17, 1906 near the island of Amchitka (M8.3) in the western Aleutian arc. However, unlike the other megathrust earthquakes along the arc, this event is thought to have been an intraplate event occurring in the shallow slab beneath the subduction zone interface.

The first megathrust event along the arc during the 20th century was the November 10, 1938 M8.6 Shumagin Island earthquake. This event ruptured an approximately 300 km long stretch of the arc from the southern end of Kodiak Island to the northern end of the Shumagin Islands and generated a small tsunami that was recorded as far south as Hawaii.

The April 1, 1946 M8.6 Unimak Island earthquake, located in the central Aleutian arc, was characterized by slow rupture followed by a devastating Pacific-wide tsunami that was observed as far south as the shores of Antarctica. Although damage from earthquake shaking was not severe locally, tsunami run-up heights were recorded as high as 42 m on Unimak Island and tsunami waves in Hilo, Hawaii also resulted in casualties. The slow rupture of this event has made it difficult to constrain the focal mechanism and depth of the earthquake, though it is thought to have been an interplate thrust earthquake.

The next megathrust earthquake occurred along the central portion of the Aleutian arc near the Andreanof Islands on March 9, 1957, with a magnitude of M8.6. The rupture length of this event was approximately 1200 km, making it the longest observed aftershock zone of all the historic Aleutian arc events. Although only limited seismic data from this event are still available, significant damage and tsunamis were observed on the islands of Adak and Unimak with tsunami heights of approximately 13 m.

The easternmost megathrust earthquake was the March 28, 1964 M9.2 Prince William Sound earthquake, currently the second largest recorded earthquake in the world. The event had a rupture length of roughly 700 km extending from Prince William Sound in the northeast to the southern end of Kodiak Island in the southwest. Extensive damage was recorded in Kenai, Moose Pass, and Kodiak but significant shaking was felt over a large region of Alaska, parts of western Yukon Territory, and British Columbia, Canada. Property damage was the largest in Anchorage, as a result of both the main shock shaking and the ensuing landslides. This megathrust earthquake also triggered a devastating tsunami that caused damage along the Gulf of Alaska, the West Coast of the United States, and in Hawaii.

The westernmost Aleutians megathrust earthquake followed a year later on February 4, 1965. This M8.7 Rat Islands earthquake was characterized by roughly 600 km of rupture. Although this event is quite large, damage was low owing to the region's remote and sparsely inhabited location. A relatively small tsunami was recorded throughout the Pacific Ocean with run-up heights up to 10.7 m on Shemya Island and flooding on Amchitka Island.

Although the Aleutian arc is highly active, seismicity is rather discontinuous, with two regions that have not experienced a large (M>8.0) earthquake in the past century: the Commander Islands in the western Aleutians and the Shumagin Islands in the east. Due to the dominantly transform motion along the western arc, there is potential that the Commander Islands will rupture in a moderate to large strike-slip earthquake in the future. The Shumagin Islands region may also have high potential for hosting a large rupture in the future, though it has been suggested that little strain is being accumulated along this section of the subduction zone, and thus associated hazards may be reduced.

East of the Aleutian arc along the Gulf of Alaska, crustal earthquakes occur as a result transmitted deformation and stress associated with the northwestward convergence of the Pacific plate that collides a block of oceanic and continental material into the North America plate. In 2002, the Denali Fault ruptured in a sequence of earthquakes that commenced with the October 23 M6.7 Nenana Mountain right-lateral strike-slip earthquake and culminated with the November 3, M7.9 Denali earthquake which started as a thrust earthquake along a then unrecognized fault and continued with a larger right-lateral strike-slip event along the Denali and Totschunda Faults.

More information on regional seismicity and tectonics


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The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
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Reply with quote  #26 
http://earthquake.usgs.gov/earthquakes/eventpage/usb000jelf#summary

M6.5 - Kepulauan Barat Daya, Indonesia 2013-09-01 11:52:32 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

[C000000db][C000000db][C000000da][C000000dc][C000000db][C000000da][C000000dc][C000000da][C000000dc]
[C000000db][C000000db][C000000da][C000000dc][C000000db][C000000da][C000000dc][C000000da][C000000dc]
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7.542°S, 128.278°E
Depth: 132.1km (82.1mi)

Event Time

  1. 2013-09-01 11:52:32 UTC
  2. 2013-09-01 20:52:32 UTC+09:00 at epicenter
  3. 2013-09-01 14:52:32 UTC+03:00 system time

Location

7.542°S 128.278°E depth=132.1km (82.1mi)

Nearby Cities

  1. 318km (198mi) ENE of Dili, East Timor
  2. 411km (255mi) ENE of Atambua, Indonesia
  3. 425km (264mi) S of Ambon, Indonesia
  4. 468km (291mi) ENE of Kefamenanu, Indonesia
  5. 318km (198mi) ENE of Dili, East Timor

Tectonic Summary

Seismotectonics of the New Guinea Region and Vicinity

The Australia-Pacific plate boundary is over 4000 km long on the northern margin, from the Sunda (Java) trench in the west to the Solomon Islands in the east. The eastern section is over 2300 km long, extending west from northeast of the Australian continent and the Coral Sea until it intersects the east coast of Papua New Guinea. The boundary is dominated by the general northward subduction of the Australia plate.

Along the South Solomon trench, the Australia plate converges with the Pacific plate at a rate of approximately 95 mm/yr towards the east-northeast. Seismicity along the trench is dominantly related to subduction tectonics and large earthquakes are common: there have been 13 M7.5+ earthquakes recorded since 1900. On April 1, 2007, a M8.1 interplate megathrust earthquake occurred at the western end of the trench, generating a tsunami and killing at least 40 people. This was the third M8.1 megathrust event associated with this subduction zone in the past century; the other two occurred in 1939 and 1977.

Further east at the New Britain trench, the relative motions of several microplates surrounding the Australia-Pacific boundary, including north-south oriented seafloor spreading in the Woodlark Basin south of the Solomon Islands, maintain the general northward subduction of Australia-affiliated lithosphere beneath Pacific-affiliated lithosphere. Most of the large and great earthquakes east of New Guinea are related to this subduction; such earthquakes are particularly concentrated at the cusp of the trench south of New Ireland. 33 M7.5+ earthquakes have been recorded since 1900, including three shallow thrust fault M8.1 events in 1906, 1919, and 2007.

The western end of the Australia-Pacific plate boundary is perhaps the most complex portion of this boundary, extending 2000 km from Indonesia and the Banda Sea to eastern New Guinea. The boundary is dominantly convergent along an arc-continent collision segment spanning the width of New Guinea, but the regions near the edges of the impinging Australia continental margin also include relatively short segments of extensional, strike-slip and convergent deformation. The dominant convergence is accommodated by shortening and uplift across a 250-350 km-wide band of northern New Guinea, as well as by slow southward-verging subduction of the Pacific plate north of New Guinea at the New Guinea trench. Here, the Australia-Pacific plate relative velocity is approximately 110 mm/yr towards the northeast, leading to the 2-8 mm/yr uplift of the New Guinea Highlands.

Whereas the northern band of deformation is relatively diffuse east of the Indonesia-Papua New Guinea border, in western New Guinea there are at least two small (<100,000 km²) blocks of relatively undeformed lithosphere. The westernmost of these is the Birds Head Peninsula microplate in Indonesia's West Papua province, bounded on the south by the Seram trench. The Seram trench was originally interpreted as an extreme bend in the Sunda subduction zone, but is now thought to represent a southward-verging subduction zone between Birds Head and the Banda Sea.

There have been 22 M7.5+ earthquakes recorded in the New Guinea region since 1900. The dominant earthquake mechanisms are thrust and strike slip, associated with the arc-continent collision and the relative motions between numerous local microplates. The largest earthquake in the region was a M8.2 shallow thrust fault event in the northern Papua province of Indonesia that killed 166 people in 1996.

The western portion of the northern Australia plate boundary extends approximately 4800 km from New Guinea to Sumatra and primarily separates Australia from the Eurasia plate, including the Sunda block. This portion is dominantly convergent and includes subduction at the Sunda (Java) trench, and a young arc-continent collision.

In the east, this boundary extends from the Kai Islands to Sumba along the Timor trough, offset from the Sunda trench by 250 km south of Sumba. Contrary to earlier tectonic models in which this trough was interpreted as a subduction feature continuous with the Sunda subduction zone, it is now thought to represent a subsiding deformational feature related to the collision of the Australia plate continental margin and the volcanic arc of the Eurasia plate, initiating in the last 5-8 Myr. Before collision began, the Sunda subduction zone extended eastward to at least the Kai Islands, evidenced by the presence of a northward-dipping zone of seismicity beneath Timor Leste. A more detailed examination of the seismic zone along it's eastern segment reveals a gap in intermediate depth seismicity under Timor and seismic mechanisms that indicate an eastward propagating tear in the descending slab as the negatively buoyant oceanic lithosphere detaches from positively buoyant continental lithosphere. On the surface, GPS measurements indicate that the region around Timor is currently no longer connected to the Eurasia plate, but instead is moving at nearly the same velocity as the Australia plate, another consequence of collision.

Large earthquakes in eastern Indonesia occur frequently but interplate megathrust events related to subduction are rare; this is likely due to the disconnection of the descending oceanic slab from the continental margin. There have been 9 M7.5+ earthquakes recorded from the Kai Islands to Sumba since 1900. The largest was the great Banda Sea earthquake of 1938 (M8.5) an intermediate depth thrust faulting event that did not cause significant loss of life.

More information on regional seismicity and tectonics


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The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
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Reply with quote  #27 
http://earthquake.usgs.gov/earthquakes/eventpage/usb000jg6b#summary


M6.0 - 191km WSW of Bella Bella, Canada 2013-09-03 20:19:06 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

[C00000023][C00000023][C00000022][C00000024][C00000023][C00000022][C00000024][C00000022][C00000024]
[C00000023][C00000023][C00000022][C00000024][C00000023][C00000022][C00000024][C00000022][C00000024]
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[gshap]

US Hazard

[ushazard]

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[mmi]
30 km
20 mi
Powered by Leaflet
51.198°N, 130.405°W
Depth: 1.0km (0.6mi)

Event Time

  1. 2013-09-03 20:19:06 UTC
  2. 2013-09-03 11:19:06 UTC-09:00 at epicenter
  3. 2013-09-03 23:19:06 UTC+03:00 system time

Location

51.198°N 130.405°W depth=1.0km (0.6mi)

Nearby Cities

  1. 191km (119mi) WSW of Bella Bella, Canada
  2. 347km (216mi) S of Prince Rupert, Canada
  3. 388km (241mi) WNW of Campbell River, Canada
  4. 388km (241mi) SSW of Terrace, Canada
  5. 592km (368mi) NW of Victoria, Canada

ShakeMap

PAGER

Impact Estimates

Historic Seismicity

City Exposure List

See PAGER XML link (above).

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Scientific

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

Summary

Preferred Location Parameters

ParameterValueUncertainty
Magnitude6.0 Mwb± 0.04
Location51.198°N, 130.405°W± 14.2 km
Depth1.0 km± 5.4 km
Number of Stations Used205
Number of Phases Used205
Minimum Distance193.7 km (1.74°)
Travel Time Residual1.48 sec
Azimuthal Gap68°
Review StatusMANUAL
Event IDusb000jg6b
See the “Contributed Solutions” for a list of all contributed location parameters.

Contributed Solutions

 

Moment Tensor

 

P-Wave Travel Times

 

Downloads

 
 

__________________
The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
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Reply with quote  #28 
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M6.5 - Izu Islands, Japan region 2013-09-04 00:18:24 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

[C000000e2][C000000e2][C000000e1][C000000e3][C000000e2][C000000e1][C000000e3][C000000e1][C000000e3]
[C000000e2][C000000e2][C000000e1][C000000e3][C000000e2][C000000e1][C000000e3][C000000e1][C000000e3]
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29.986°N, 138.811°E
Depth: 404.8km (251.5mi)

Event Time

  1. 2013-09-04 00:18:24 UTC
  2. 2013-09-04 09:18:24 UTC+09:00 at epicenter
  3. 2013-09-04 03:18:24 UTC+03:00 system time

Location

29.986°N 138.811°E depth=404.8km (251.5mi)

Nearby Cities

  1. 356km (221mi) SSW of Hachijo-jima, Japan
  2. 494km (307mi) SSE of Shingu, Japan
  3. 514km (319mi) S of Oyama, Japan
  4. 515km (320mi) SSE of Owase, Japan
  5. 637km (396mi) S of Tokyo, Japan

Tectonic Summary

Seismotectonics of the Philippine Sea and Vicinity

The Philippine Sea plate is bordered by the larger Pacific and Eurasia plates and the smaller Sunda plate. The Philippine Sea plate is unusual in that its borders are nearly all zones of plate convergence. The Pacific plate is subducted into the mantle, south of Japan, beneath the Izu-Bonin and Mariana island arcs, which extend more than 3,000 km along the eastern margin of the Philippine Sea plate. This subduction zone is characterized by rapid plate convergence and high-level seismicity extending to depths of over 600 km. In spite of this extensive zone of plate convergence, the plate interface has been associated with few great (M>8.0) ‘megathrust’ earthquakes. This low seismic energy release is thought to result from weak coupling along the plate interface (Scholz and Campos, 1995). These convergent plate margins are also associated with unusual zones of back-arc extension (along with resulting seismic activity) that decouple the volcanic island arcs from the remainder of the Philippine Sea Plate (Karig et al., 1978; Klaus et al., 1992).

South of the Mariana arc, the Pacific plate is subducted beneath the Yap Islands along the Yap trench. The long zone of Pacific plate subduction at the eastern margin of the Philippine Sea Plate is responsible for the generation of the deep Izu-Bonin, Mariana, and Yap trenches as well as parallel chains of islands and volcanoes, typical of circum-pacific island arcs. Similarly, the northwestern margin of the Philippine Sea plate is subducting beneath the Eurasia plate along a convergent zone, extending from southern Honshu to the northeastern coast of Taiwan, manifested by the Ryukyu Islands and the Nansei-Shoto (Ryukyu) trench. The Ryukyu Subduction Zone is associated with a similar zone of back-arc extension, the Okinawa Trough. At Taiwan, the plate boundary is characterized by a zone of arc-continent collision, whereby the northern end of the Luzon island arc is colliding with the buoyant crust of the Eurasia continental margin offshore China.

Along its western margin, the Philippine Sea plate is associated with a zone of oblique convergence with the Sunda Plate. This highly active convergent plate boundary extends along both sides the Philippine Islands, from Luzon in the north to the Celebes Islands in the south. The tectonic setting of the Philippines is unusual in several respects: it is characterized by opposite-facing subduction systems on its east and west sides; the archipelago is cut by a major transform fault, the Philippine Fault; and the arc complex itself is marked by active volcanism, faulting, and high seismic activity. Subduction of the Philippine Sea Plate occurs at the eastern margin of the archipelago along the Philippine Trench and its northern extension, the East Luzon Trough. The East Luzon Trough is thought to be an unusual example of a subduction zone in the process of formation, as the Philippine Trench system gradually extends northward (Hamburger et al., 1983). On the west side of Luzon, the Sunda Plate subducts eastward along a series of trenches, including the Manila Trench in the north, the smaller less well-developed Negros Trench in the central Philippines, and the Sulu and Cotabato trenches in the south (Cardwell et al., 1980). At its northern and southern terminations, subduction at the Manila Trench is interrupted by arc-continent collision, between the northern Philippine arc and the Eurasian continental margin at Taiwan and between the Sulu-Borneo Block and Luzon at the island of Mindoro. The Philippine fault, which extends over 1,200 km within the Philippine arc, is seismically active. The fault has been associated with major historical earthquakes, including the destructive M7.6 Luzon earthquake of 1990 (Yoshida and Abe, 1992). A number of other active intra-arc fault systems are associated with high seismic activity, including the Cotabato Fault and the Verde Passage-Sibuyan Sea Fault (Galgana et al., 2007).

Relative plate motion vectors near the Philippines (about 80 mm/yr) is oblique to the plate boundary along the two plate margins of central Luzon, where it is partitioned into orthogonal plate convergence along the trenches and nearly pure translational motion along the Philippine Fault (Barrier et al., 1991). Profiles B and C reveal evidence of opposing inclined seismic zones at intermediate depths (roughly 70-300 km) and complex tectonics at the surface along the Philippine Fault.

Several relevant tectonic elements, plate boundaries and active volcanoes, provide a context for the seismicity presented on the main map. The plate boundaries are most accurate along the axis of the trenches and more diffuse or speculative in the South China Sea and Lesser Sunda Islands. The active volcanic arcs (Siebert and Simkin, 2002) follow the Izu, Volcano, Mariana, and Ryukyu island chains and the main Philippine islands parallel to the Manila, Negros, Cotabato, and Philippine trenches.

Seismic activity along the boundaries of the Philippine Sea Plate (Allen et al., 2009) has produced 7 great (M>8.0) earthquakes and 250 large (M>7) events. Among the most destructive events were the 1923 Kanto, the 1948 Fukui and the 1995 Kobe (Japan) earthquakes (99,000, 5,100, and 6,400 casualties, respectively), the 1935 and the 1999 Chi-Chi (Taiwan) earthquakes (3,300 and 2,500 casualties, respectively), and the 1976 M7.6 Moro Gulf and 1990 M7.6 Luzon (Philippines) earthquakes (7,100 and 2,400 casualties, respectively). There have also been a number of tsunami-generating events in the region, including the Moro Gulf earthquake, whose tsunami resulted in more than 5000 deaths.

More information on regional seismicity and tectonics

ShakeMap

PAGER

Impact Estimates

Historic Seismicity

City Exposure List

See PAGER XML link (above).

Did You Feel It? Tell Us!

Scientific

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

Summary

Preferred Location Parameters

ParameterValueUncertainty
Magnitude6.5 Mwp± 0.06
Location29.986°N, 138.811°E± 12.1 km
Depth404.8 km± 9.1 km
Number of Stations Used63
Number of Phases Used70
Minimum Distance359.6 km (3.23°)
Travel Time Residual1.29 sec
Azimuthal Gap38°
Review StatusMANUAL
Event IDusb000jgfc
See the “Contributed Solutions” for a list of all contributed location parameters.

Contributed Solutions

 

P-Wave Travel Times

 

Downloads

 

__________________
The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
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Reply with quote  #29 
http://earthquake.usgs.gov/earthquakes/eventpage/usb000jgju#summary


M6.5 - 77km SSW of Atka, Alaska 2013-09-04 02:32:33 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

[C00000003][C00000003][C00000002][C00000004][C00000002][C00000004]
[C00000003][C00000003][C00000002][C00000004][C00000002][C00000004]
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GSHAP Hazard

[gshap]

US Hazard

[ushazard]

ShakeMap

[mmi]
30 km
20 mi
Powered by Leaflet
51.592°N, 174.760°W
Depth: 39.9km (24.8mi)

Event Time

  1. 2013-09-04 02:32:33 UTC
  2. 2013-09-03 14:32:33 UTC-12:00 at epicenter
  3. 2013-09-04 05:32:33 UTC+03:00 system time

Location

51.592°N 174.760°W depth=39.9km (24.8mi)

Nearby Cities

  1. 77km (48mi) SSW of Atka, Alaska
  2. 1532km (952mi) SSE of Anadyr', Russia
  3. 1809km (1124mi) E of Petropavlovsk-Kamchatskiy, Russia
  4. 1826km (1135mi) E of Yelizovo, Russia
  5. 2618km (1627mi) W of Whitehorse, Canada

Tectonic Summary

Seismotectonics of Alaska

The Aleutian arc extends approximately 3,000 km from the Gulf of Alaska in the east to the Kamchatka Peninsula in the west. It marks the region where the Pacific plate subducts into the mantle beneath the North America plate. This subduction is responsible for the generation of the Aleutian Islands and the deep offshore Aleutian Trench.

The curvature of the arc results in a westward transition of relative plate motion from trench-normal (i.e., compressional) in the east to trench-parallel (i.e., translational) in the west, accompanied by westward variations in seismic activity, volcanism, and overriding plate composition. The Aleutian arc is generally divided into three regions: the western, central, and eastern Aleutians. Relative to a fixed North America plate, the Pacific plate is moving northwest at a rate that increases from roughly 60 mm/yr at the arc's eastern edge to 76 mm/yr near its western terminus. The eastern Aleutian arc extends from the Alaskan Peninsula in the east to the Fox Islands in the west. Motion along this section of the arc is characterized by arc-perpendicular convergence and Pacific plate subduction beneath thick continental lithosphere. This region exhibits intense volcanic activity and has a history of megathrust earthquakes.

The central Aleutian arc extends from the Andreanof Islands in the east to the Rat Islands in the west. Here, motion is characterized by westward-increasing oblique convergence and Pacific plate subduction beneath thin oceanic lithosphere. Along this portion of the arc, the Wadati-Benioff zone is well defined to depths of approximately 200 km. Despite the obliquity of convergence, active volcanism and megathrust earthquakes are also present along this margin.

The western Aleutians, stretching from the western end of the Rat Islands in the east to the Commander Islands, Russia, in the west, is tectonically different from the central and eastern portions of the arc. The increasing component of transform motion between the Pacific and North America plates is evidenced by diminishing active volcanism; the last active volcano is located on Buldir Island, in the far western portion of the Rat Island chain. Additionally, this portion of the subduction zone has not hosted large earthquakes or megathrust events in recorded history. Instead, the largest earthquakes in this region are generally shallow, predominantly strike-slip events with magnitudes between M5-6. Deeper earthquakes do occur, albeit rather scarcely and with small magnitudes (M<4), down to approximately 50 km.

Most of the seismicity along the Aleutian arc results from thrust faulting that occurs along the interface between the Pacific and North America plates, extending from near the base of the trench to depths of 40 to 60 km. Slip along this interface is responsible for generating devastating earthquakes. Deformation also occurs within the subducting slab in the form of intermediate-depth earthquakes that can reach depths of 250 km. Normal faulting events occur in the outer rise region of the Aleutian arc resulting from the bending of the oceanic Pacific plate as it enters the Aleutian trench. Additionally, deformation of the overriding North America plate generates shallow crustal earthquakes.

The Aleutian arc is a seismically active region, evidenced by the many moderate to large earthquakes occurring each year. Since 1900, this region has hosted twelve large earthquakes (M>7.5) including the May 7, 1986 M8.0 Andreanof Islands, the June 10, 1996 M7.9 Andreanof Islands, and the November 17, 2003 M7.8 Rat Islands earthquakes. Six of these great earthquakes (M8.3 or larger) have occurred along the Aleutian arc that together have ruptured almost the entire shallow megathrust contact. The first of these major earthquakes occurred on August 17, 1906 near the island of Amchitka (M8.3) in the western Aleutian arc. However, unlike the other megathrust earthquakes along the arc, this event is thought to have been an intraplate event occurring in the shallow slab beneath the subduction zone interface.

The first megathrust event along the arc during the 20th century was the November 10, 1938 M8.6 Shumagin Island earthquake. This event ruptured an approximately 300 km long stretch of the arc from the southern end of Kodiak Island to the northern end of the Shumagin Islands and generated a small tsunami that was recorded as far south as Hawaii.

The April 1, 1946 M8.6 Unimak Island earthquake, located in the central Aleutian arc, was characterized by slow rupture followed by a devastating Pacific-wide tsunami that was observed as far south as the shores of Antarctica. Although damage from earthquake shaking was not severe locally, tsunami run-up heights were recorded as high as 42 m on Unimak Island and tsunami waves in Hilo, Hawaii also resulted in casualties. The slow rupture of this event has made it difficult to constrain the focal mechanism and depth of the earthquake, though it is thought to have been an interplate thrust earthquake.

The next megathrust earthquake occurred along the central portion of the Aleutian arc near the Andreanof Islands on March 9, 1957, with a magnitude of M8.6. The rupture length of this event was approximately 1200 km, making it the longest observed aftershock zone of all the historic Aleutian arc events. Although only limited seismic data from this event are still available, significant damage and tsunamis were observed on the islands of Adak and Unimak with tsunami heights of approximately 13 m.

The easternmost megathrust earthquake was the March 28, 1964 M9.2 Prince William Sound earthquake, currently the second largest recorded earthquake in the world. The event had a rupture length of roughly 700 km extending from Prince William Sound in the northeast to the southern end of Kodiak Island in the southwest. Extensive damage was recorded in Kenai, Moose Pass, and Kodiak but significant shaking was felt over a large region of Alaska, parts of western Yukon Territory, and British Columbia, Canada. Property damage was the largest in Anchorage, as a result of both the main shock shaking and the ensuing landslides. This megathrust earthquake also triggered a devastating tsunami that caused damage along the Gulf of Alaska, the West Coast of the United States, and in Hawaii.

The westernmost Aleutians megathrust earthquake followed a year later on February 4, 1965. This M8.7 Rat Islands earthquake was characterized by roughly 600 km of rupture. Although this event is quite large, damage was low owing to the region's remote and sparsely inhabited location. A relatively small tsunami was recorded throughout the Pacific Ocean with run-up heights up to 10.7 m on Shemya Island and flooding on Amchitka Island.

Although the Aleutian arc is highly active, seismicity is rather discontinuous, with two regions that have not experienced a large (M>8.0) earthquake in the past century: the Commander Islands in the western Aleutians and the Shumagin Islands in the east. Due to the dominantly transform motion along the western arc, there is potential that the Commander Islands will rupture in a moderate to large strike-slip earthquake in the future. The Shumagin Islands region may also have high potential for hosting a large rupture in the future, though it has been suggested that little strain is being accumulated along this section of the subduction zone, and thus associated hazards may be reduced.

East of the Aleutian arc along the Gulf of Alaska, crustal earthquakes occur as a result transmitted deformation and stress associated with the northwestward convergence of the Pacific plate that collides a block of oceanic and continental material into the North America plate. In 2002, the Denali Fault ruptured in a sequence of earthquakes that commenced with the October 23 M6.7 Nenana Mountain right-lateral strike-slip earthquake and culminated with the November 3, M7.9 Denali earthquake which started as a thrust earthquake along a then unrecognized fault and continued with a larger right-lateral strike-slip event along the Denali and Totschunda Faults.

More information on regional seismicity and tectonics


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The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
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Reply with quote  #30 
http://earthquake.usgs.gov/earthquakes/eventpage/usb000jkmw#summary

M6.6 - 5km ESE of Ciudad Tecun Uman, Guatemala 2013-09-07 00:13:29 UTC

Summary

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

General

[C0000003e][C0000003e][C0000003d][C0000003f][C0000003e][C0000003d][C0000003f][C0000003d][C0000003f]
[C0000003e][C0000003e][C0000003d][C0000003f][C0000003e][C0000003d][C0000003f][C0000003d][C0000003f]
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Guatemala
14.644°N, 92.104°W
Depth: 67.0km (41.6mi)

Event Time

  1. 2013-09-07 00:13:29 UTC
  2. 2013-09-06 18:13:29 UTC-06:00 at epicenter
  3. 2013-09-07 03:13:29 UTC+03:00 system time

Location

14.644°N 92.104°W depth=67.0km (41.6mi)

Nearby Cities

  1. 5km (3mi) ESE of Ciudad Tecun Uman, Guatemala
  2. 15km (9mi) NE of Suchiate, Mexico
  3. 26km (16mi) WSW of Coatepeque, Guatemala
  4. 28km (17mi) SSW of Malacatan, Guatemala
  5. 171km (106mi) W of Guatemala City, Guatemala

Tectonic Summary

The September 7, 2013 (UTC) Guatemala earthquake (Mw6.5) occurred near the west coast of Guatemala in the Middle American trench. The event occurred at or near the interface between the Cocos and North America plates.   The style of faulting based on the W-phase source mechanism indicates slip likely occurred on a shallow thrust fault consistent with the subduction interface.  At the latitude of this event, the Cocos plate moves towards the north-northeast with respect to the North American plate at a rate of 78 mm/yr.

The broad scale tectonics of the western and southwestern coast of Central America are dominated by the northeastward subduction of the Cocos oceanic plate beneath the North America plate. Thrust- and normal-type earthquakes are a common occurrence along this plate boundary and the Guatemala region, with events occurring both within the subduction zone and in the overriding plate. Over the past 40 years, 27 events of M6.0 or greater have occurred within 300km of the September 2013 event. Events of note in this region include earthquakes on November 2012 Mw7.4 offshore of Guatemala, which killed 39 people; September 1993 M­w­7.2 offshore of Chiapas, Mexico, which killed one person; and December 1983 Mw7.0 offshore of Guatemala. Other early 20th century earthquakes in the Guatemala region include August 1942 Mw7.9, which killed 38 and April 1902 M7.5, which killed more than 5000 people.

ShakeMap

PAGER

Impact Estimates

Historic Seismicity

City Exposure List

See PAGER XML link (above).

Did You Feel It? Tell Us!

Scientific

Location and Magnitude contributed by: USGS, NEIC, Golden, Colorado (and predecessors)

Summary

Preferred Location Parameters

ParameterValueUncertainty
Magnitude6.6 MwwNot Specified
Location14.644°N, 92.104°W± 11.7 km
Depth67.0 km± 2.8 km
Number of Stations Used319
Number of Phases Used320
Minimum Distance45.6 km (0.41°)
Travel Time Residual0.97 sec
Azimuthal Gap29°
Review StatusMANUAL
Event IDusb000jkmw
See the “Contributed Solutions” for a list of all contributed location parameters.

Contributed Solutions

 

Moment Tensor

 

P-Wave Travel Times

 

Downloads

 

__________________
The universe is a hairball. It was created by Fritz the Cat. Einstein said the universe was like a plate of spaghetti. Still, you don't want to know what transpired between him and Elsa to bring about that idea.
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