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Paper No. 11
Presentation Time: 5:00 PM


HIGHLAND, Lynn M., U.S. Geological Survey, Geologic Hazards Team, Box 25046, MS 966, Denver Federal Center, Denver, CO 80225 and SUN, Ping, Institute of Geomechanics, Chinese Academy of Geological Sciences, No. 11, Minzu Daxue Nanlu, Haidian District, Beijing, 100081, China,

The Magnitude 7.9 (Mw) Wnechuan, China, Earthquake of May 12, 2008 caused at least 88,000 casualties, of which one third are estimated to be due to the thousands of earthquake-induced landslides. In addition to damaging the built enviornment, the landslides caused profound changes to the natural environment. The affected area is mountainous, featuring densely-vegetated, steep-walled, narrow canyons. Although the majority of the landslides were newly-developed, many older ones were reactivated. The landslides destroyed an estimated 400,000 hectares of cropland and caused the loss of 67,018 hectares of natural ecosystems, comprising forests, shrubs, grassland, and wetlands. Primarily due to vegetation denudation, the landslides changed one of the world's most biodiverse temperate forests, the Hengduan Mountain region, an important carbon sink. The stripping of vegetation and its subsequent decomposition increased the potential for substantial atmospheric CO2 emissions. Landslides altered soil properties by causing increased aeration in the upper layers, resulting in increased soil temperature, which may lead to droughts. Some landslides were hundreds of million cubic meters in volume, and moved at extremely high speed, causing phenomena such as air blasts, flowslides, and sturzstroms. The explosive nature of the landslide movement, together with the voluminous landslide debris, caused rapid damming of rivers and streams, forming 256 landslide dams. As a result, waterway morphology, (such as drainage patters) was altered, as was the quality of drinking water, and fish habitat, primarily due to sediment content. landslide debris and denuded slopes increased the severity and number of deadly debris flows, which have since occurred in the affected region. Destructive landslides impacted the many giant panda reserves in the area. In addition to severely denuding the slopes of bamboo, the panda's food source, the landslides fragmented the landscape, crippling the panda's ability to travel to food sources, and find and associate with others. The landslide-associated destruction of the panda reserves' infrastructure and wild lands as well as the damaged transportation routes to the area has severely reduced the crucial tourist business in the region.
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