A massive earthquake has destroyed buildings and homes, most heavily in the Sichuan region. One town is in danger of being flooded due to a collapsing dam.
On Monday May 12, 2008, at approximately 06:30 UTC, a major earthquake shook the entire country of China. As of May 14, the death toll is at 15,000; 14,000 missing; 26,000 still buried. According to the USGS website, the epicenter was located at 31.015 degrees N and 103.365 degrees E – 90 km (55 miles) northwest of Chengdu, Sichuan, China and 1545 km (960 miles) southwest of Beijing, China.
Earthquake Details
The earthquake was a magnitude 7.9 earthquake at a depth of about 19 km (11.8 miles). Earthquakes throughout China are not uncommon, but this is the largest magnitude earthquake to strike the Sichuan region in several decades. A magnitude 7.5 earthquake in the northwest margin of Sichuan Basin killed more than 9,300 people on August 25, 1933. The May 12 earthquake as already claimed 15,000 lives and the death toll is expected to rise.
Geology of the Area
This earthquake was a result of motion on a fault in the northwestern portion of the Sichuan Basin located in central China. A structural basin is a geological feature that forms as a result of tectonic warping of previously flat-lying strata, or layers of sediment. Central Asia has undergone tectonic warping on a continental scale due to the crashing of the Indian Plate into the Eurasia Plate at a velocity of about 50 millimeters per year. The Sichuan Basin is also called the “Red Basin” and it is the principal gas-producing region in China.
Fault Movement
According to the location of the epicenter, geologists have determined that the earthquake is a result of movement on the Longmenshaun fault or a fault tectonically related to this fault. This fault is under constant stress from the slow convergence of crustal material from the Tibetan Plateau to the west, against crust underlying the Sichuan Basin. This fault is a northeast-striking reverse fault. Imagine taking a layered cake and slicing through the top of the cake with a knife that is pointed northeast and slightly at an angle. If the portion of the cake that is on top of the knife slides up, that is a reverse fault; if it slides down, that is a normal fault.
Where Was It Felt?
The large magnitude of this earthquake and relatively shallow depth has led to extensive damage in areas closest to the epicenter and shaking in Beijing, almost 1000 miles from the epicenter, has been reported on the US Geological Survey’s Did You Feel It? website. Reports of the most intense shaking were felt in the cities of Mianyang and Tianpeng, where people reported the movement as violent and buildings were heavily damaged. The earthquake was also felt in parts of Bangladesh, Taiwan, Thailand and Vietnam.
Sources:
US Geological Survey
CNN
