PLANETARY TREMORS: Powerful 7.1 Earthquake Strikes Near Japan's Kumamoto - Tsunami Warnings Issued! [MAPS + TECTONIC SUMMARY + VIDEOS]

USGS earthquake location.

April 15, 2016 - JAPAN - A magnitude-7.1 earthquake has hit Japan near the city of Kumamoto on the island of Kyushu, the Japan Meteorological Agency reported. Tsunami warnings have been issued.

The epicenter of the quake in southern Japan was located at a shallow depth of 10 kilometers, near the area where a 6.5 earthquake struck on Thursday.

#tsunami advisory on the coastal area of Ariake Sea and Yatsushiro Sea on the western coast of #Kumamoto. Magnitude 7.1 #earthquake #jishin

— Aiko Doden (@nhk_asianvoices) April 15, 2016

The latest footage from Kumamoto in Japan, where a 7.4-magnitude earthquake has hit https://t.co/0ZqutBrWwW https://t.co/HxsmZ5ZvLe

— Sky News (@SkyNews) April 15, 2016

According to the US Geological Survey, the quake had a magnitude of 7.0 and its epicenter was located just 1 km southwest of the city of Kumamoto.

USGS shakemap intensity.

An aftershock of 5.8 magnitude has also been reported in the area.

"Tsunami warnings or advisories are currently in effect," Japan Meteorological Agency said.


WATCH: Japan quake death toll rises.

The tsunami advisory has been issued for the Ariake and Yatsushiro Seas.

The advisory warns of a possible wave of one meter in height, Japan's NHK broadcaster said.

USGS Tectonic Summary

The April 15, 2016 M 7.0 earthquake north of Kumamoto, on the island of Kyushu in southwest Japan, occurred as the result of strike-slip faulting at shallow depth. Focal mechanisms for the earthquake indicate slip occurred on either a left-lateral fault striking to the northwest, or on a right-lateral fault striking northeast. While the earthquake occurred several hundred kilometers northwest of the Ryukyu Trench, where the Philippine Sea plate begins its northwestward subduction beneath Japan and the Eurasia plate, the shallow depth and faulting mechanism of this earthquake indicate it occurred on a crustal fault within the upper Eurasia plate. At the location of this event, the Philippine Sea plate converges with Eurasia towards the northwest at a velocity of 58 mm/yr.

The April 15, 2016, M 7.0 event (UTC 16:25:06) occurred one day after a series of foreshocks in the same region, which included M 6.2 and M 6.0 earthquakes. The April 14 events resulted in at least 9 fatalities and over 800 injuries.

In contrast to this recent sequence of shallow earthquakes, most seismicity in the Kyushu region is related to the subduction of the Philippine Sea plate at depth. Just thirteen M 5+ earthquakes have occurred at shallow depths (< 50 km) within 100 km of the April 2016 events over the preceding century. In January and April of 1975, two shallow events with magnitudes of M 5.8 and M 6.1 - 40 km and 65 km to the northwest of the April 2016 earthquake, respectively – caused injuries, but no known fatalities. A shallow M 6.6 earthquake in March 2005, just off the north coast of Kyushu and 110 km north of the April 2016 event, caused over 1000 injuries and at least one fatality.

Mapped faults in the region generally trend east-west or northeast-southwest, in agreement with the right-lateral plane of preliminary focal mechanisms, and the trend of early aftershocks. Since the April 14, M 6.2 event (12:26:36 UTC), 19 other shocks have been located, including the latest M 7.0 earthquake.

USGS 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 (Magnitude greater than 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.

USGS plate tectonics.

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 (Magnitude greater than 8.0) earthquakes and 250 large (Magnitude greater than 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



- RT | USGS.

DISASTER IMPACT: Japan Earthquake Update - Tens Of Thousands Flee In Fear Of Aftershocks And Volcanoes; 9 People Killed And Over 850 Injured! [VIDEO]

A collapsed house is seen after an earthquake in Kumamoto, southern Japan.
© REUTERS/Kyodo

April 14, 2016 - JAPAN - Tens of thousands of people have been evacuated from earthquake-hit southern Japan as dozens of aftershocks struck and officials monitored nearby volcanoes for signs of activity.

A total of 44,000 people were evacuated late on Thursday in the town of Mashiki after a magnitude-6.4 earthquake collapsed buildings and damaged other infrastructure. Nine people have been confirmed dead, ranging in age from 29 to 94. A further eight are in serious condition, and more than 850 were injured.

The Japan Meteorological Agency (JMA) has warned there are likely to be strong aftershocks for the next week and advised people to stay away from any buildings that look unstable.

There are also concerns about volcanic activity in the wake of the quake.

The island of Kyushu, where the earthquake happened, is a highly volcanic area. A level 2 warning - meaning people should not approach a volcano's crater - has been in place for Asosan in Kumamoto prefecture on the island since November 2015.


WATCH: Japan quake damage being assessed as mass evacuation continues.

Head teacher Sosuke Tanaka hosted about 300 people at West Hiroyasu elementary school, which was turned into an evacuation centre, and said many in Kumamoto suffered a sleepless night. "We saw earthquakes through the evening, so many did not manage to get a proper night's rest," he said. About 120 aftershocks have been observed since the initial earthquake, more than 15 of which measured 3 or higher on the Japanese intensity scale.

At the Mashiki gymnastics centre, Yoko Marume said more and more people have been evacuating since the earthquake. "We had about 200 overnight, but now, I would say there are about 500," she told the Guardian. "People have been gathering here from across the city, it's a big space. Most are shaken, many believe that their houses could fall down."

Junko Seto, an 80-year-old woman, told the Asahi Shimbun: "My husband returned to our house to see how things looked, and he says there isn't room to stand because of the mess caused."

"I want to go home and get things in order, but with the aftershocks I am too scared to go home yet."

Japan's Self Defense Forces have entered Hiroyasu, in a mountainous region of Kumamoto prefecture, to inspect the damage caused to roads and housing by the earthquake. "There has been significant damage to wooden housing around here," Tanaka told the Guardian.

Rations of bread and water were distributed to evacuees in the early hours of Friday. Marume said lunch boxes had arrived for evacuees at the gymnastics centre.

The initial temblor measured a maximum 7 on the Japanese intensity scale, equivalent to the force of the 1995 Kobe disaster and the March 11, 2011, earthquake in east Japan. So far, however, the damage caused in Kyushu seems low in comparison.

A spokeswoman for the JMA said: "We are watching closely, but we have seen no change in Asosan or other volcanoes since the earthquake."

Sakurajima, in neighbouring Kagoshima prefecture, erupted in February. - Guardian.

PLANETARY TREMORS: Very Strong 6.4 And 6.0 Magnitude Earthquakes Strike Japan - Tsunami Warning Issued, But Later Cancelled; Several AFTERSHOCKS; Rescuers Battle To Free People Trapped Under Rubble; Fires Breakout; At Least 19 HOMES COLLAPSED! [MAPS + TECTONIC SUMMARY + PHOTOS + VIDEOS]

USGS earthquake location.

April 14, 2016 - JAPAN - A 6.4 magnitude earthquake has struck east of Kumamoto, Japan, according to the Japan Meteorological Agency. It had a depth of 10 kilometers (6.2 miles).

The quake hit at 9:26 p.m. local time (12:26 GMT), eight kilometers (4.97 miles) from the city of Tamana.

USGS shakemap intensity.

The earthquake left behind damage to buildings, as well as a fire.

Keisukei Urata, an official in Uki, told AP that he saw walls around houses collapsing.

"Papers, files, flower vases and everything fell on the floor," Kasumi Nakamura, an official in the village of Nishihara, located near the epicenter, told NHK. He said the rattling started small but then grew violent, lasting about 30 seconds, adding that there were aftershocks.

La classique scène de la pancarte d'un bureau de chaîne télé qui vibre. #Kumamoto pic.twitter.com/jiAwfUmqEp

— Thomas Bertrand (@ThomasKyoto) April 14, 2016

The situation at the apartment building of a friend in #Kumamoto after M6.4 quake. pic.twitter.com/XHmA9wR9kB

— Kjeld Duits (@KjeldDuits) April 14, 2016

熊本県のスーパーがヤバイ pic.twitter.com/AcGXqSiNZQ

— アリエッティ@EARTH.福岡3日5日 (@m_s_k_h) April 14, 2016

震度7の地震があった熊本市内のブックオフの様子 pic.twitter.com/OtkJfCfkE1

— かいざー (@MECCYAEEYA) April 14, 2016

One aftershock measuring 5.7 struck about 40 minutes after the quake, according to the Japan Meteorological Agency.

The US Geological Survey (USGS) put the quake at a 6.2 magnitude.

The Japan Meteorological Agency originally issued a tsunami warning, but later canceled it.


WATCH: Dozens injured after 6.4-strong earthquake hits east of Kumamoto.

Second large earthquake hits Japan measuring 6.0 in magnitude as rescuers battle to free people trapped in rubble

Fires burn after a second quake hit Japan.
© Sky News

A second huge earthquake has hit Japan measuring 6.0 in magnitude.

This comes as the nation was coming to terms with the destruction caused by the 6.4 tremor which struck earlier today.
It is unclear how much damage the latest quake has caused but there is reportedly, currently no tsunami warning in place.

Fires were seen breaking out after nineteen homes reportedly collapsed near to the site of the tremor.

Rescue workers are currently battling to free those trapped in the rubble. After the first tremor, the Nuclear Regulation Authority said there were no irregularities at three nuclear plants on the southernmost island of Kyushu and nearby Shikoku.

Some high-speed trains were halted as a precaution. Japanese media showed watermelons falling from shelves at asupermarket in Kumamoto.

A quake of magnitude 9 struck offshore north of Tokyo in March 2011, causing tsunami waves along the coast which killed nearly 20,000 people and triggered a meltdown at a nuclear powerplant.

The first tremor caused widespread damage.
© Getty

The earlier quake struck 11 km (7 miles) east of the city of Kumamoto, the U.S. Geological Survey reported. It initially said the magnitude was 6.2 but revised it down. Japanese public broadcaster NHK said the quake registered 6.4.

There was no tsunami warning, but Japan's chief government spokesman, Yoshihide Suga, said several buildings had collapsed. He gave no more details. Footage captured some dramatic scenes during the earlier quake with one camera catching officer workers diving for cover as the quake hit.

Watermelons fell from store shelves and lay crushed on the floor of a supermarket in Kumamoto city, near the epicentre, NHK footage showed.

Objects fell from shelves and staff ducked under desks as the quake shook the NHK office in Kumamoto, video showed.

Tectonic Summary

The April 14, 2016 M 6.4 earthquake north of Kumamoto, on the island of Kyushu in southwest Japan, occurred as the result of strike-slip faulting at shallow depth. Focal mechanisms for the earthquake indicate slip occurred on either a left-lateral fault striking to the northwest, or on a right-lateral fault striking northeast. While the earthquake occurred several hundred kilometers northwest of the Ryukyu Trench, where the Philippine Sea plate begins its northwestward subduction beneath Japan and the Eurasia plate, the shallow depth and faulting mechanism of this earthquake indicate it occurred on a crustal fault within the upper Eurasia plate. At the location of this event, the Philippine Sea plate converges with Eurasia towards the northwest at a velocity of 58 mm/yr.

Moderate-to-large, shallow earthquakes in Kyushu are infrequent – most seismicity in the region is related to the subduction of the Philippine Sea plate at depth. Thirteen M 5+ earthquakes have occurred at shallow depths (> 50 km) within 100 km of the April 2016 event over the past century. In January and April of 1975, two shallow events with magnitudes of M 5.8 and M 6.1 - 40 km and 65 km to the northwest of the April 2016 earthquake, respectively – caused injuries, but no known fatalities. A shallow M 6.6 earthquake in March 2005, just off the north coast of Kyushu and 110 km north of the April 2016 event, caused over 1000 injuries and at least one fatality.

Mapped faults in the region generally trend east-west or northeast-southwest, in agreement with the right-lateral plane of preliminary focal mechanisms, and the trend of early aftershocks. In the first three hours after the M 6.4 event (12:26:36 UTC), 7 aftershocks have been located, the largest of which is a M 6.0 event at 15:03:47 UTC.

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 (Magnitude greater than 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.

USGS plate tectonics.

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 (Magnitude greater than 8.0) earthquakes and 250 large (Magnitude greater than 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



- RT | Daily Mirror | USGS.

PLANETARY TREMORS: Major Global Seismic Uptick - Strong 6.2 Magnitude Earthquake Strikes Off The Coast Of Japan; No Tsunami Threat! [MAPS + TECTONIC SUMMARY]

USGS earthquake location.

January 11, 2016 - JAPAN - The U.S. Geological Survey is reporting a 6.2-magnitude earthquake off Japan.

The quake was reported just after 2 a.m. Tuesday morning local time (1700 GMT Monday), 984 kilometers (611 miles) north of Tokyo.

It was west of Hokkaido island.

USGS shakemap intensity.

The tremor was initially measured by the USGS as a 6.1 magnitude.

The depth was reported at 236 kilometers.

There is no current tsunami warning from the Pacific Tsunami Warning Center. - Statesman Journal.

Seismotectonics of the Kuril-Kamchatka Arc

The Kuril-Kamchatka Arc extends approximately 2,100 km from Hokkaido, Japan along the Kuril Islands and the Pacific coast of the Kamchatka Peninsula, until terminating at its intersection with the Aleutian arc south of the Commander Islands, Russia. It marks the region where the Pacific plate subducts into the mantle beneath the Okhotsk mircoplate, a proposed regional subdivision of the larger North America plate. This subduction is responsible for the generation of the Kuril Islands chain, volcanoes along the entire arc, and the deep Kuril-Kamchatka Trench. Relative to a fixed North America plate, the Pacific plate is moving northwest at a rate that increases from 79 mm/yr near the northern end of the arc to 83 mm/yr adjacent to Hokkaido.

In the southern section of the Kuril arc oblique subduction results in the partitioning of stress into both trench-normal thrust earthquakes (e.g., the 12/03/1995 M 7.9 Kuril Island event) and trench-parallel strike-slip earthquakes (e.g., the 10/16/1994 M 6.7 Kuril Island event). This oblique convergence also drives the southwestern translation of the Kuril Arc, and its collision with the Japan Arc. The collision in turn drives the uplift of the Hidaka Mountains, and causes northwest-southeast oriented compressional earthquakes across Hokkaido.

USGS plate tectonics.

North of approximately 44° latitude, adjacent to the island of Urup, convergence becomes dominantly trench normal. In this area, cross-sections of the subduction zone reveal a well-defined Wadati-Benioff zone extending to depths of 650 km, supporting assumptions that the Pacific plate is relatively old and has been subducting for close to 100 Myr. As the arc approaches its northern terminus off the coast of the Kamchatka Peninsula, the character of subduction changes again due to the entrainment of the Meiji Seamount and the influence of transform motion along westernmost extent of the Aleutian Arc. The angle of subduction decreases from 55 to 35 degrees from south to north, and the maximum depth of seismicity decreases from ~600 km to ~200 km, causing a northwestern deviation in the volcanic front.

The Kuril-Kamchatka Arc is one of the most seismically active regions in the world. Deformation of the overriding North America plate and associated microplates generates shallow crustal earthquakes, while slip at the subduction zone interface between the Pacific and North America plates generates interplate earthquakes that extend from near the base of the trench to depths of 40 to 60 km. The aftershock zones of great historic earthquakes abut one another along the strike of the arc but generally do not overlap; sections of the subduction zone have typically experienced earthquakes of a consistent size at fairly regular recurrence intervals, though the length of seismicity catalogs is typically shorter than the expected repeat times of the largest earthquakes known to have occurred in the region.

Patterns in along-arc seismicity can reveal seismic gaps, zones where no great ruptures have occurred for an anomalously long period of time. In the Kuril region, a gap between Simushir Island and Onekotan Island that had remained unruptured by a large earthquake since 1780 was the site of an M 8.3 event on November 15, 2006. Minutes after the November 15 earthquake, aftershocks began rupturing one or more faults near the outer rise region seaward of the Kuril-Kamchatka Trench, adjacent to the location of the main shock. On January 13, 2007, two months after the 2006 event, a great (M 8.1) normal faulting earthquake occurred in this same region. Because the January 2007 event ruptured within the aftershock zone of the November 2006 quake, it is speculated to be the result of changes in the regional stress field following the earlier event, despite occurring on a different fault. The inferred coupling of the 2006 and 2007 events make them one of the largest earthquake doublets to have ever been recorded.

The Kuril-Kamchatka region frequently experiences large (Magnitude greater or equal to 7) and great (Magnitude greater or equal to 8) earthquakes. In the 114 years since 1900, 133 large and 12 great earthquakes have occurred along the arc. Damaging tsunamis followed several of the large interplate megathrust earthquakes, including the September 25, 2003 M 8.3 Hokkaido earthquake, and the November 6, 1958 M 8.4 Etorofu event. The February 3, 1923 M 8.4 Kamchatka earthquake generated an 8 m transoceanic tsunami. On October 13, 1963, a M 8.5 megathrust earthquake off the coast of the island of Urup generated a large tsunami in the Pacific Ocean and the Sea of Okhotsk, with run-up wave heights of up to 4-5 m.

The largest megathrust earthquake to occur along the arc in the 20th century was the November 4, 1952 M 9.0 event, to date the 5th largest instrumentally recorded earthquake in history. This earthquake was followed by a devastating tsunami with run-up wave heights as high as 12 m along the coast of Paramushir, causing significant damage to the city of Severo-Kurilsk. Intraplate earthquakes have also been known to cause significant damage in the region. On October 4, 1994, a large (M8.3) intraplate event occurred within the subducted oceanic lithosphere of the Pacific plate off the coast of Shikotan Island, causing intense ground shaking, landslides, and a tsunami with run-up heights of up to 10 m on the island.

While most large earthquakes along the Kuril-Kamchatka Arc occur at shallow or intermediate depths, the region also hosts large events that rupture at depths greater than 300 km. The most significant of these deep-focus earthquakes to date was the May 24, 2013 M 8.3 event beneath the Sea of Okhotsk, currently the largest deep-focus earthquake on record. The earthquake occurred as the result of normal faulting within the subducted Pacific slab approximately 600 km below the Earth's surface, and was felt as far away as Moscow, Russia, nearly 6,500 km to the west.

More information on regional seismicity and tectonics

- USGS.

PLANETARY TREMORS: Strong Magnitude 6.2 Earthquake Strikes Off Japan's Bonin Islands - USGS! [MAPS + TECTONIC SUMMARY]

Bonin islands, Japan. © Google Maps

November 21, 2015 - JAPAN - An earthquake of magnitude 6.2 struck 112 km (70 miles) southeast of Japan's Bonin islands on Friday, about 1,000 km south of the capital Tokyo, the US Geological Survey said.

The quake at a depth of 10 km (6 miles), hit at 0540 GMT.

There were no immediate reports of damage or casualties. - The New Indian Express.

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 (Magnitude greater than 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.

USGS plate tectonics for the region

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 (Magnitude greater than 8.0) earthquakes and 250 large (Magnitude greater than 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

- USGS.

PLANETARY TREMORS: Magnitude 5.7 Earthquake Strikes Off Japan's Kyushu!

USGS shakemap intensity

November 13, 2015 - JAPAN - A magnitude 5.7 earthquake struck off Japan's southern island of Kyushu, the U.S. Geological Survey said on Saturday.

The quake, initially reported as a magnitude 5.9, struck at 4:20 a.m. on Sunday (1920 GMT on Saturday) 94 miles (151 km) west of Kagoshima. It was shallow, at a depth of only 16.2 miles (26 km) below the seabed. - Reuters.

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 (Magnitude greater than 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.

USGS plate tectonics for the region

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 (Magnitude greater than 8.0) earthquakes and 250 large (Magnitude greater than 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

- USGS.

PLANETARY TREMORS: Powerful 7.0 Magnitude Earthquake Hits Off The Southern Coast Of Japan - Tsunami Alert Issued! [MAPS+TECTONIC SUMMARY]

USGS earthquake location

November 13, 2015 - JAPAN - A tsunami warning has been issued for parts of Japan after a magnitude 7.0 earthquake struck off its south-western coast.

The Japan Meteorological Agency said waves of up to one metre (3ft) could hit the western coast of Kagoshima prefecture and Satsunan islands.

It said the quake happened at the depth of about 10km (six miles).

USGS shakemap intensity

The US Geological Survey said the tremor struck some 159km south-west of the town of Makurazaki.

"Get out of the water and leave the coast immediately," the JMA's warning said.

"As the strong current will continue, do not get in the sea or approach coasts until the advisory is cleared," it added.

Tsunami advisories issued for portions of southwestern #Japan, including the Tanegashima Yakushima areas
The Weather Channel.

In 2011, a massive earthquake caused a tsunami that left more than 18,000 people dead or missing in north-eastern Japan.

Some 230,000 people have yet to return to their home towns since the disaster. - BBC.

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 (Magnitude greater than 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.

USGS plate tectonics for the region

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 (Magnitude greater than 8.0) earthquakes and 250 large (Magnitude greater than 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

- USGS.

PLANETARY TREMORS: Major Global Seismic Uptick Continues As The Black Celestial Event Nears - MEGA-QUAKE Warning In Rumblings Off Japan's Coast Alarms Scientists!

May 14, 2015 - JAPAN - Scientists say they’ve recorded low frequency shaking on the ocean floor that could be the result of increasing pressure, similar to what was released during the devastating 2011 Japan earthquake and tsunami.

Scientists had previously detected a slow moving underwater shift – or foreshock – along the plate responsible for the 2011 earthquake that sent shock waves around the world and devastated Santa Cruz and Crescent City harbors in California.

In a 2012 article, researchers suggested that such a shift may have caused “substantial stress loading” and unstable conditions that triggered the 9.0 magnitude quake and tsunami blamed for killing more than 15,000 people.

Now a second team of researchers says a similar pattern is emerging in a subduction zone where two tectonic plates are engaged in a “slow” earthquakes that would previously have gone unnoticed.

A view of the damage from the 2011 Japan earthquake and tsunami. (Noboru Hashimoto/AFP/Getty Images)

“Monitoring of offshore seismicity off southern Kyushu, Japan, recorded a complete episode of low-frequency tremor, lasting for 1 month, that was associated with very-low-frequency earthquake activity,” reads the abstract in the journal Science.

These quakes moved in waves along the tectonic ridge and stopped abruptly rather than dissipating slowly and releasing the energy, potentially increasing stress that could be released in a “mega thrust” earthquake, according to IFL science.

The hope is that the discovery of such rumbling in an area where big quakes originate may be a first step in early detection of larger tremors with the potential to cause widespread structural damage and trigger tsunamis. - CBS.

 

PLANETARY TREMORS: Major Global Seismic Uptick Continues As The Black Celestial Event Nears - Powerful 6.8 Magnitude Earthquake Strikes Off Japan's Honshu Island; No Tsunami Warning Issued!

Earthquake 3D map.

May 12, 2015 - JAPAN - A powerful 6.8 earthquake has struck off the eastern coast of Japan’s Honshu island, USGS and Japan Meteorological Agency report. Shaking has been felt in Tokyo.

The quake struck at 6:13am local time at a depth of almost 50 kilometers. While USGS originally reported the quake at 6.9 magnitude, JMA measured it at 6.6. No casualties or damage have yet been reported.

USGS earthquake location.

No tsunami warning was issued by JMA and according to the Pacific Tsunami Warning Center, based on all available data a “destructive pacific-wide tsunami” is not expected. No warning has been issued for the US state of Hawaii.

No abnormalities were reported at the Fukushima nuclear power plant, which was crippled by an earthquake and tsunami in 2011.

USGS shakemap intensity.

However, some trains were reportedly delayed on the Tohoku Line between Fukushima and Sendai prefectures following tremors.

Onagawa and Higashidori nuclear power plants also reported no abnormalities. - RT.


WATCH: Strong Magnitude 6.8 Earthquake Strikes Off Japan Coast (near Fukushima).

 

Tectonic Summary - Seismotectonics of Japan and Vicinity

Japan and the surrounding islands straddle four major tectonic plates: Pacific plate; North America plate; Eurasia plate; and Philippine Sea plate. The Pacific plate is subducted into the mantle, beneath Hokkaido and northern Honshu, along the eastern margin of the Okhotsk microplate, a proposed subdivision of the North America plate. Farther south, the Pacific plate is subducted beneath volcanic islands along the eastern margin of the Philippine Sea plate. This 2,200 km-long zone of subduction of the Pacific plate is responsible for the creation of the deep offshore Ogasawara and Japan trenches as well as parallel chains of islands and volcanoes, typical of Circumpacific island arcs. Similarly, the Philippine Sea plate is itself subducting under the Eurasia plate along a zone, extending from Taiwan to southern Honshu that comprises the Ryukyu Islands and the Nansei-Shoto trench.

USGS plate tectonics for the region. [PDF]

Subduction zones at the Japanese island arcs are geologically complex and produce numerous earthquakes from multiple sources. Deformation of the overriding plates generates shallow crustal earthquakes, whereas slip at the interface of the plates generates interplate earthquakes that extend from near the base of the trench to depths of 40 to 60 km. At greater depths, Japanese arc earthquakes occur within the subducting Pacific and Philippine Sea plates and can reach depths of nearly 700 km. Since 1900, three great earthquakes occurred off Japan and three north of Hokkaido. They are the M8.4 1933 Sanriku-oki earthquake, the M8.3 2003 Tokachi-oki earthquake, the M9.0 2011 Tohoku earthquake, the M8.4 1958 Etorofu earthquake, the M8.5 1963 Kuril earthquake, and the M8.3 1994 Shikotan earthquake.

More information on regional seismicity and tectonics

- USGS.

PLANETARY TREMORS: Strong 5.7 Magnitude Earthquake Strikes Japan's Hachijo-jima Island - Tsunami Warnings Lifted; Small Waves Seen Along Izu And Ogasawara Islands! [MAPS + TECTONIC SUMMARY]

USGS earthquake location

May 2, 2015 - JAPAN - An earth tremor of magnitude 5.7 has struck 185 kilometres south-south-east of Japan's Izu islands on Saturday, the United States Geological Survey has said.

The USGS at first put the quake at 6.1, but later revised it to a weaker reading. Japanese authorities put the magnitude of the quake at 5.9.

The tremor was at a shallow depth of 10 kilometres.

USGS shakemap intensity

Tsunami warnings were lifted for the Izu and Ogasawara islands after they experienced small waves following the earthquake, public broadcaster NHK said.

Tsunamis of up to 50 centimetres were recorded in the islands stretching south of Tokyo, before the Japan Meteorological Agency lifted warnings at 4:10 am local time, NHK said. - ABC News Australia.

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 (Magnitude greater than 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.

USGS plate tectonics for the region

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 (Magnitude greater than 8.0) earthquakes and 250 large (Magnitude greater than 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

- USGS.

PLANETARY TREMORS: Strong 6.2 Magnitude Earthquake Strikes Off Southern Japan - No Tsunami Warning! [MAPS + TECTONIC SUMMARY]

USGS earthquake location

February 25, 2015 - JAPAN - A 6.2 magnitude earthquake has struck off the southern coast of Japan, according to the US Geological Survey.

The quake, with its epicenter around 290km (175 miles) southeast of Hachijo-jima, Izu Islands, struck at a depth of 65km (38 miles).

The event comes just hours after another 4.4 quake took place just off the Kuril Islands, disputed with Russia.

USGS shakemap intensity

The tremors also come a day after another quake struck off the eastern coast, measuring 5.8, with the epicenter about 100km east of the city of Miyako.

An earlier even in mid-February hit 6.9 magnitude, with promise of 1-meter tsunami waves, hitting off the northern coast of Japan, also close to MIyako. It struck in the same region where a devastating 9.0-magnitude quake had in 2011 - the one that caused the tsunami, which led to the Fukushima nuclear power plant meltdown.

Earthquakes are common in the region. Japan straddles four major tectonic plates, with one of them – the Pacific Plate – subducted beneath the island of Hokkaido, the northeasternmost of Japan’s four main islands. - RT.

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 (Magnitude greater than 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.

USGS plate tectonics for the region

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 (Magnitude greater than 8.0) earthquakes and 250 large (Magnitude greater than 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

- USGS.