Interpreting the Coseismic Uplift and Subsidence of the Longmen Shan Foreland Basin System during the Wenchuan Earthquake by a Elastic Flexural Model

• Published in: Acta geologica Sinica (Beijing) Vol. 90; no. 2; pp. 555 - 566
• Main Authors: Zhaokun, YAN, Yong, LI, Chongjian, SHAO, Rongjun, ZHOU, Liang, YAN, Guohua, ZHAO, Binglei, YAN
• Format: Journal Article
• Language: English
• Published: Richmond Blackwell Publishing Ltd 01.04.2016; Wiley Subscription Services, Inc; State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation(CDUT), Chengdu 610059, China%Sichuan Earthquake Administration, Chengdu 610041, China
• Edition: English ed.
• Subjects: Basins; coseismic uplift and subsidence; Earthquakes; Flexing; flexural model; foreland basin system; Levelling; Longmen Shan; Mathematical analysis; Mathematical models; Sea level; Subsidence; Uplift; Wenchuan Earthquake; 四川盆地; 地震; 挠曲; 有效弹性厚度; 模型方程; 盆地沉降; 隆起; 龙门山; flexural model; Longmen Shan; foreland basin system; Wenchuan Earthquake; coseismic uplift and subsidence
• ISSN: 1000-9515; 1755-6724
• DOI: 10.1111/1755-6724.12690

The coseismic surface uplift of the Longmen Shan（LMS） created an instantaneous topographic load over the western margin of the Sichuan Basin, where surface subsidence, decreasing eastward, has been measured using several methods, such as GPS, SAR and levelling. Using an elastic flexural model, we aim to interpret the coseismic surface uplift and subsidence, and constrain the effective lithospheric elastic thickness（Te） of the Sichuan Basin. Using different effective elastic thickness values for the Sichuan Basin, a series of subsidence curves were computed by the elastic flexure model equation for a broken elastic plate. The curves, produced by models using an effective elastic thickness of 30–40 km, provided the best fit to the general pattern of observed coseismic subsidence of the Sichuan Basin. However, the calculated subsidence（-40–70 cm） at the front of the LMS is evidently lower than the observed values（-100 cm）, suggesting that the effective elastic thickness therein should be lower. These results indicate that the lithospheric strength may decrease westward from the Sichuan Basin to the LMS.