Static Coulomb stress changes on faults caused by the 2008 Mw 7.9 Wenchuan, China earthquake

The 12 May 2008 Mw 7.9 Wenchuan earthquake has changed the regional tectonic stress field significantly. It is important to know how such a change affects the tectonic loading processes of the faults and therefore the seismic potential of the region. Utilizing the slip distribution of the Wenchuan earthquake as the driving source we compute the changes of Coulomb failure stress (CFS) on the neighborhood faults assuming a friction coefficient of 0.4. Our results show that the CFSs have increased on average 1.6 × 104 and 1.8 × 104 Pa at the SW and NE ends of the Longmen Shan, 2.6 × 104 Pa at the western segment of the Qinling Southern Frontal, 2.0 × 104 Pa at the northernmost part of the Longriba, 1.4 × 104 Pa at the southernmost part of the Xianshuihe, 1.3×104 Pa at the southeast end of the East Kunlun, 9.0 × 103 Pa at the southernmost part of the Minjiang, 2.9 × 103 Pa at the Baiyu, and 3.5 × 103 Pa at the Longxian–Baoji faults. Recurring times of these faults are advanced, about 39 and 230 years for the SW and NE segments of the Longmen Shan, ∼ 5.5 years toward the east end of the East Kunlun, and ∼ 1.6 years for the SE segments of the Xianshuihe faults. The quake also relaxed the CFS significantly on most part of the Minjiang, southwest segment of the Longriba, northwest segment of the Xianshuihe, southeast segment of the Yushu–Maqu, north part of the Xiaojinhe, Daliangshan, and Anninghe faults, with the CFS reductions ranging on average of 1.8 × 104, 2.5 × 104, 7.1 × 103, 2.4 × 103, 1.0 × 103, 1.0 × 103, and 1.6 × 103 Pa, respectively. Recurring times of these faults are delayed, up to 185 years for the south segment of the Minjiang, up to 18 years for the northeast of the Longriba, up to 9.8 years for the West Qinling Northern Frontal, and up to 2.7 years for the northwest segment of the Xianshuihe faults, respectively. We test sensitivity of the changes of CFS to variations of apparent fiction coefficient μ′, and find that the senses of CFS change are almost invariant with μ′ except at the Minjiang, Longriba, and Qinling Southern Frontal faults, where large normal stresses on faults induced by the Wenchuan earthquake could play an important role in manifesting CFS change when μ′ is large. The CFS changes vary slowly along seismogenic depth on most of the receiver faults.