April 13, 2014 - SOLOMON ISLANDS - A tsunami warning has been issued after a strong, 7.5-magnitude quake
hit near the Solomon Islands in the southwestern Pacific for the second
time in hours. It follows a 7.6-quake that rocked the region overnight.
The shallow earthquake, originally registered at 7.7 magnitude, but later revised down to 7.5, was centered about 114 kilometers south of Kirakira in the Solomon Islands, at a depth of 20 kilometers, the US Geological Survey reported.
An aftershock quake of 5.7 magnitude followed the initial one just minutes after.
A tsunami warning was immediatly issued for the Solomon Islands, Vanuatu and Papua New Guinea, according to the Pacific Tsunami Warning Center.
Small tsunami waves have been detected in the Solomon Islands, while the warning continues only for the Solomon Islands. The previous tsunami warning for Vanuatu and Papua New Guinea was canceled.
The previous quake, estimated at 7.6, hit the region overnight. It struck 100 kilometers southeast of Kirakira at a depth of almost 30 kilometers. A tsunami warning was also issued for the first quake, but it lasted only for a few hours.
No damage or casualties have been reported. The USGS upgraded its pager status to ‘green’, meaning that “there is a low likelihood of casualties and damage.”
The Vanuatu Meteorological Service has issued a separate warning saying that the initial tsunami wave is estimated to hit the islands of Vanuatu about 12:45 am local time Monday.
“People are advised to listen to all radio outlets,” the service said. “The next advisory will be updated today at 12:30am.”
The Solomon Islands are a sovereign country consisting of a large number of islands in Oceania, lying to the east of Papua New Guinea and covering a land area of 28,400 square kilometers.
They are located on the eastern margin of the Australia plate, which is one of the most seismically active areas of the world due to high rates of convergence between the Australia and Pacific tectonic plates.
In early April Chile was rocked by several earthquakes that killed six people and displaced almost 1 million. The quakes triggered deadly fires, which killed eight people and left at least 3,000 people homeless. - RT.
The April 13 earthquake occurred less than 24 hours and approximately 20 km to the southwest of a M 7.7 strike-slip earthquake on April 12, 2014. While the April 12 strike-slip earthquake likely represented Australia:Pacific plate boundary faulting, the April 13 earthquake is located south of the plate boundary at a depth of approximately 35 km, and as such may represent tearing of the Australia plate to accommodate the abrupt change in Australian plate interaction with the Pacific plate (subduction to the north and west; left-lateral translation to the east).
The region of the April 12 earthquake is very seismically active, with 28 earthquakes of M6+ occurring within 100 km and 62 events of M7+ within 500 km since 1900. The majority of these earthquakes are grouped to the northwest around the Solomon Islands and to the east near Vanuatu and the Santa Cruz Islands. Notable earthquake within 100 km include a doublet of M7.0 events in November 1978, events of M7.1 in 1931 and 1937, and an M7.2 in 1910. The most recent local event prior to the April 12 earthquake was an M6.0 on April 4, 2014 94 km to the NW. The April 12 earthquake also occurred about 950 km to the SE of an earthquake sequence south of Bougainville Island, Papua New Guinea that began with an M6.1 on April 11, 2014. On February 6, 2013, an M8.0 struck offshore of the Santa Cruz Islands about 340 km east of the April 12 event. The 2013 earthquake triggered a regional tsunami of about 1.5 m and was followed by aftershocks of M7.0 and two of M7.1.
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". - USGS.
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| USGS earthquake location map. |
The shallow earthquake, originally registered at 7.7 magnitude, but later revised down to 7.5, was centered about 114 kilometers south of Kirakira in the Solomon Islands, at a depth of 20 kilometers, the US Geological Survey reported.
An aftershock quake of 5.7 magnitude followed the initial one just minutes after.
A tsunami warning was immediatly issued for the Solomon Islands, Vanuatu and Papua New Guinea, according to the Pacific Tsunami Warning Center.
Small tsunami waves have been detected in the Solomon Islands, while the warning continues only for the Solomon Islands. The previous tsunami warning for Vanuatu and Papua New Guinea was canceled.
 |
| USGS earthquake shakemap intensity map. |
The previous quake, estimated at 7.6, hit the region overnight. It struck 100 kilometers southeast of Kirakira at a depth of almost 30 kilometers. A tsunami warning was also issued for the first quake, but it lasted only for a few hours.
No damage or casualties have been reported. The USGS upgraded its pager status to ‘green’, meaning that “there is a low likelihood of casualties and damage.”
The Vanuatu Meteorological Service has issued a separate warning saying that the initial tsunami wave is estimated to hit the islands of Vanuatu about 12:45 am local time Monday.
 |
| View of Honiara, the capital city of Solomon Islands (Photo by Jenny Scott / flickr.com) |
“People are advised to listen to all radio outlets,” the service said. “The next advisory will be updated today at 12:30am.”
The Solomon Islands are a sovereign country consisting of a large number of islands in Oceania, lying to the east of Papua New Guinea and covering a land area of 28,400 square kilometers.
They are located on the eastern margin of the Australia plate, which is one of the most seismically active areas of the world due to high rates of convergence between the Australia and Pacific tectonic plates.
In early April Chile was rocked by several earthquakes that killed six people and displaced almost 1 million. The quakes triggered deadly fires, which killed eight people and left at least 3,000 people homeless. - RT.
Tectonic Summary.
The April 13, 2014 M 7.5 Solomon Islands earthquake occurred as the
result of nearly pure reverse faulting on an approximately east-west
oriented structure near the oceanic trench that marks the plate boundary
between the Australia and Pacific plates. At the location of the
earthquake, the Australia Plate converges with and slips past the
Pacific plate at a rate of 95 mm/yr. The April 13 earthquake occurred
along a portion of this plate boundary that transitions from thrust to
transform tectonics between the New Britain Trench to the northwest and
the New Hebrides Trench farther east. The earthquake occurred about 110
km SSE of Kirakira, Solomon Islands.The April 13 earthquake occurred less than 24 hours and approximately 20 km to the southwest of a M 7.7 strike-slip earthquake on April 12, 2014. While the April 12 strike-slip earthquake likely represented Australia:Pacific plate boundary faulting, the April 13 earthquake is located south of the plate boundary at a depth of approximately 35 km, and as such may represent tearing of the Australia plate to accommodate the abrupt change in Australian plate interaction with the Pacific plate (subduction to the north and west; left-lateral translation to the east).
The region of the April 12 earthquake is very seismically active, with 28 earthquakes of M6+ occurring within 100 km and 62 events of M7+ within 500 km since 1900. The majority of these earthquakes are grouped to the northwest around the Solomon Islands and to the east near Vanuatu and the Santa Cruz Islands. Notable earthquake within 100 km include a doublet of M7.0 events in November 1978, events of M7.1 in 1931 and 1937, and an M7.2 in 1910. The most recent local event prior to the April 12 earthquake was an M6.0 on April 4, 2014 94 km to the NW. The April 12 earthquake also occurred about 950 km to the SE of an earthquake sequence south of Bougainville Island, Papua New Guinea that began with an M6.1 on April 11, 2014. On February 6, 2013, an M8.0 struck offshore of the Santa Cruz Islands about 340 km east of the April 12 event. The 2013 earthquake triggered a regional tsunami of about 1.5 m and was followed by aftershocks of M7.0 and two of M7.1.
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". - USGS.
