Crustal deformation in western Sichuan region and implications for 12 May 2008 Ms 8.0 earthquake

Abstract

We have established 65 GPS stations and derive a detailed horizontal deformation distribution in western Sichuan region, in conjunction with previous measurements at additional 90 stations. The resulting velocity field shows that strike‐slip fault system here plays a significant role in adjusting crustal movements (in direction and magnitude) along the eastern borderland of the Tibetan Plateau. We find Xianshuihe fault is essentially creeping in its southeasternmost portion with left‐lateral slip rate of 8.4 ± 2.8 mm/a. We report ∼5.6 mm/a left‐lateral slip rate across Anninghe and Daliangshan fault. Mabian fault slips left‐laterally at the rate of 2.5 ± 1.4 mm/a with nearly null fault‐normal motion. Deformation across Litang and Yunongxi fault appear insignificant at present time. Our results reveal recently ruptured Longmenshan fault has both right‐lateral slip rate and compressional rate close to 2.0 ± 1.0 mm/a, implying that the Longmenshan fault indeed absorbs some northeastern motion of Tibetan Plateau and likely causes strain accumulation there, which leads to the breakout of the 12 May 2008 Ms 8.0 earthquake. We also find several domains with markedly localized strain rates, which are associated with individual structures.