7/16/2007 Honshu, Japan

Updated 9/22/2007


This 6.6 Magnitude quake hit at 10:13 AM local time (01:13 GMT), just off the west coast of the island of Honshu in central Japan. The epicenter was 45 miles west of the city of Nigata and 150 miles to the northwest of Tokyo. It was followed a couple of hours later by a 6.8 M quake nearby. Although the second quake was stronger, it was focused depper and thus cause less damage. According to the US Geological Service account of the quake, these quakes were different enough that the second one is not considered an aftershock of the first.

The earthquake caused damage to 875 buildings, especially older ones, 1,088 injuries and 11 deaths. The shaking was so strong that people said they couldn't stand during the quake. A nuclear power plant remains shut down two months after the quake due to damage that resulted in the release of radiation. This accident follows several other incidents at nuclear power plants in Japan that have called into question the safety of Japan's extensive nuclear power program.

Japan is located at the western edge of the Pacific Plate, where it interacts with the Eurasian Plate and some small tectonic plates inbetween. This results in many earthquakes as these plates interact. In 2004 a 6.6 M quake in the same general area killed 40 people and injured 3,000. The US Geological Service account of the quake describes the geology in more detail. (See the Plate Tectonics page for more information on these processes.) The US Geological Survey (USGS) is an invaluable resource in understanding and tracking earthquakes.

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9/12/2007 Sumatra Earthquake

Updated 9/20/2007

An 8.4 Magnitude earthquake hit southern Sumatra at 11:10GMT on September 12, 2007. 6:10pm local time. The epicenter was 80 miles SW of the city of Bengkulu. This is the same area as the June 11, 2000 7.9 magnitude quake. This is the third quake over 8.0 magnitude this year, following last month's Peruvian quake and the April Solomon Islands quake (see below). 23 deaths have been reported so far. This is quite low for a major earthquake in this area. Over 45,000 buildings have been damaged but casualties have been surprisingly low for a quake of this size. There have been numerous strong aftershocks, including one 7.9 magnitude and one 6.8. Both of these are strong enough to be considered major quakes on their own. In all, there have been 23 aftershocks greater than 5.0 Magnitude in the week following the quake.

There were fears of a tsunami throughout the Indian Ocean area. However, aside from a 3 ft wave in the local Sumatra area that didn't cause any damage, there hasn't been one. After each of the larger quakes, warnings were issued and then withdrawn when no tsunami occured. This nervousness is understandable with memories still fresh from the disastrous 2004 tsunami, which was caused by a larger (8.9 M) quake further north along the southern Sumatra coast. Tsunami predictions are difficult because the size of a tsunami following a large quake is dependent on conditions on the seabed at the epicenter. This is often not known. What we do know is that a large undersea earthquake could produce a tsunami. The larger the quake, the greater the chance of a tsunami. With a limited amount of time to get the word out, governments have been quick to issue a warning since the 2004 tsunami, which hit many areas without warning. This quake was large, although considerably smaller than the 2004 one. In fact, it was larger than any quake to hit the the US outside of Alaska in the last 300 years.

The quake is caused by the subduction of the ocean beneath the Sumatra coast. The subduction zone stretches over 2800 miles along the southern coast of Sumatra and Java. This movement created strain in the crust that is relieved by quakes in different areas of the subduction zone. That is why there have been so many large quakes along the southern edge of the Sumatra and Java coasts. Each quake relieves pressure in one section of the zone but in the process builds pressure in neighboring sections. Over a period of 150-300 years the whole zone will experience earthquakes. The process continues as the Australian Plate is being forced under the smaller plates to the north, between the Eurasian Plate and the Pacific Plate. This is certainly the most seismically active area of the world. The smaller quake 7 years ago relieved some strain but apparently not enough, especially given the other quakes on other segments of the subduction zones in the interim.

US Geological Survey Paghttp://theearthquakemuseum.weebly.com/plate-tectonics.html"> Plate Tectonics page for more information on these processes.) The US Geological Survey (USGS) is an invaluable resource in understanding and tracking earthquakes.

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8/15/2007 Peruvian Earthquake

Updated 8/18/2007

The 8.0 M earthquake occurred at 23:41 GMT on Wednesday August 15 (6:41 PM local time). The epicenter was on the coast 92 miles south of Lima and 68 miles NW of Ica, which sustained the greatest damage. The quake was felt as far away as Arequipa, Peru's 2nd largest city 250 miles to the south and the site of an 8.1 M quake in 2001. Shaking was reported to have lasted 2 minutes.

The death toll is over 500, with reports from some areas still not in. The cities of Ica, with 261,000 people, and Pisco, a city of 116,000, have been hardest hit. Reports talk of massive destruction. 127 bodies were recovered from one church that collapsed during a funeral service. Thousands more have been injured and tens of thousands are homeless. People have been camping out for fear of further building collapses. There have been several strong aftershocks. Three days after the quake, although aid was arriving, many people were desperate for food. There have been reports of looting. Some aid shipments have been stopped and looted by people who apparently couldn't stand to see it go by, while they were in such need. President Alan Garcia sent in the army to restore order. Aid distribution has been slowed by damage to the Pan American highway, the major transportation link in the area.

Winter temperatures in this desert region drop in the night and people camping out have been burning salvaged wood from destroyed buildings for warmth. There is a shortage of blankets and warm clothing.

680 prisoners escaped from a maximum security prison after it was damaged in the quake. Police have been trying to apprehend them, in addition to the pressing needs of maintaining order and aiding the victims. Some of the prisoners reported turned themselves in because conditions were so bad in the area that they apparently decided that prison was preferable.

The earthquake was felt strongly in Peru's capital, Lima. People ran into the streets. The power went off and there were reports of loud noise and lights in the sky at the time of the quake. One person said there was lightning caused by power surges as the grid went down.

A tsunami may have been generated in the immediate area, but widescale tsunami warnings in the Pacific were cancelled after a few hours. There have not been reports of tsunami damage.

Earthquakes over 8.0 Magnitude are classified as Great Earthquakes and are capable of wide scale devastation in a heavily populated area. They occur worldwide once every year or two. However, many occur in lightly populated areas and do not cause a lot of damage. This is the second great earthquake this year, following the April Solomon Islands quake (see below). The 2004 Sumatra earthquake and tsunami, by contrast, at 9.0M released 10 times the energy of this quake.

The USGS tectonic summary for this quake said: "This earthquake occurred at the boundary between the Nazca and South American tectonic plates. The two plates are converging at a rate of 77 mm per year. The earthquake occurred as thrust-faulting on the interface between the two plates, with the South American plate moving up and seaward over the Nazca plate. Coastal Peru has a history of very large earthquakes. The August 15 shock originated just south of the source region of the magnitude 8.1 earthquake of October 1974 and just north of the source regions of major earthquakes that occurred in August 1942 (magnitude 7.7) and 1996 (magnitude 7.7). The largest coastal Peru earthquake of the last two centuries was the magnitude 9 earthquake of 1868, which was centered about 700 km southeast of the August 15 earthquake. The 1868 shock produced a tsunami that killed several thousand people along the South American coast and also caused damage in Hawaii."

(See the Plate Tectonics page for more information on these processes.) The US Geological Survey (USGS) is an invaluable resource in understanding and tracking earthquakes.

US Geological Survey page on this quake

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4/1/2007 Solomon Islands Earthquake and Tsunami

Updated 4/4/2007

The 8.1 M earthquake occurred at 20:49 GMT on Sunday April 1 (7:40 AM April 2 local time), followed by a tsunami up to 30 feet high near the epicenter. Several villages were destroyed by the tsunami on the islands nearest the epicenter. At least 30 people were killed and thousands left homeless. However, the news getting out of the area is very sparse. For days the story, if any, has been that several villages have been damaged to an indeterminate degree.

Earthquakes over 8.0 Magnitude are classified as Great Earthquakes and are capable of wide scale devastation in a heavily populated area. They occur worldwide once every year or two. The Solomon Islands have only 500,000 people spread out on small islands in the South Pacific. The quake was the result of the subduction of the Australian Plate, and some smaller plates, under the Pacific Plate.

(See the Plate Tectonics page for more information on these processes.) The US Geological Survey (USGS) is an invaluable resource in understanding and tracking earthquakes.

The US Geological Survey page on this quake

See also the following news stories:

3/6/2007 Sumatra Earthquake

Updated 3/9/2007

A Magnitude 6.4 earthquake, which occurred at 3:49 GMT, 10:49 AM local time March 6, 2007 in southern Sumatra, Indonesia caused at least 52 deaths and over 500 serious injuries. Thousands are homeless. Most casulaties came when buildings collapsed, over 4,000 buildings were damaged, including homes, schools and mosques. The epicenter was 30 miles from the city of Padang and 580 miles NW of Jakarta. Buildings swayed as far away as Singapore, 250 miles away. People fled away from the coast fearing another tsunami, but this quake did not trigger one, since it was located on land, not undersea. A 6.1 Magnitude aftershock was felt 2 hours later. Thousands stayed outdoors, afraid that more aftershocks will cause more buildings to collapse,

Indonesia may be the most seismically active area of the world, with frequent earthquakes. This quake occurred on the Sumatra fault, which runs the length of the island. Unlike the powerful subduction quakes of December 26, 2004 and March 28, 2005 in which the Australian plate dives under the Sunda Plate, the Sumatra fault produces strike slip quakes in which the edge of the Sunda plate is being pulled sideways relative to the rest of the plate. The subduction quakes of 2004 and 2005 were located further up the coast, about 300-400 miles to the NW of this one.

This area is known for twin quakes, with almost identical quakes occuring within 3 hours of eachother in the same area in 1926.

(See the Plate Tectonics page for more information on these processes.) The US Geological Survey (USGS) is an invaluable resource in understanding and tracking earthquakes.

The US Geological Survey page on this quake

See also the following news stories: