Did the 2008 Wenchuan earthquake lead to a net volume loss?

Abstract

The topographic evolution of mountain landscapes is a coupling process of tectonic rock uplift, landslide erosion, and valley incision etc. A widely accepted notion is that an earthquake will build up the mountainous topography, whereas some researchers suggest that the 2008 Wenchuan earthquake tumbled down the mountain because the wasting mass volume due to landsliding is two to six times larger than the gain volume caused by rock uplift. The purpose of this paper is to compare the wasting mass volume due to seismic landsliding with the gain volume caused by rock uplift related to the 2008 Wenchuan event based on a new detailed landslide inventory prepared by visual interpretation of aerial photos and satellite images of high resolutions. The results show that about 5.9 km3 materials, generated by nearly 200,000 landslides triggered by the Wenchuan earthquake, are distributed in the landslide intensity area. Although the landslides volume is larger than the published volume of tectonic rock uplift (2.6 _ 1.2 km3), it is rather smaller than that from the previous study. We think it is not enough only to account for the co-seismic landslide volume and uplifted volume in the study of landscape evolution of the Longmenshan mountain area where the Wenchuan event took place. Orogenic evolution is affected by a variety of factors, such as co-seismic and interseismic crustal uplift, and isostatic compensation of mass removed from the surface of the earth which leads to orogenic growth, whereas co-seismic landslides and river erosion can destroy mountainous topography.