HR: 1340h
AN: T43B-1353    [Abstracts]
TI: Coulomb stress change on the Xiaojiang and the Red River faults, southeastern Tibetan Plateau, from the 1970 Ms=7.7 Tonghai earthquake
AU: * He, J
EM: jkhe@itpcas.ac.cn
AF: Institute of Tibetan Plateau Research, Chinese Academy of Sciences, No.18,ShuangQing Road, Haidian District, Beijing, 100086, China
AU: Lu, S
EM: sjlu@itpcas.ac.cn
AF: Institute of Tibetan Plateau Research, Chinese Academy of Sciences, No.18,ShuangQing Road, Haidian District, Beijing, 100086, China
AU: Wang, X
EM: xgwang@itpcas.ac.cn
AF: Institute of Tibetan Plateau Research, Chinese Academy of Sciences, No.18,ShuangQing Road, Haidian District, Beijing, 100086, China
AB: The Xiaojiang and the Red River faults are two large-scale active faults in the southeastern Tibetan Plateau. Over the last 500 years, about 4 M >7.0 earthquakes, including the 1833 M~8 Songmin event, and 2 M~7.0 earthquakes occurred on the Xiaojiang fault and the Red River fault, respectively. In 1970, a devastating earthquake with Ms=7.7 happened near Tonghai of Yunnan province. This event raptures the Qujiang fault, a relatively small active fault in the corner where the right-lateral Xiaojing fault and the right-lateral Red River fault are conjugated. To investigate if the 1970 Ms=7.7 event would enhance the potential of seismicity along the two large-scale strike- slip faults, we explore quantitatively, in the framework of the Coulomb failure stress ( CFS), the idea that both coseismic and postseismic stress changes from this event may increase the likelihood of failure on some segments of the Xiaojiang and the Red River faults. A wide range of lithospheric rheology has been tested, associated with available ruptures of the 1970 event. Numerical results show that on some segments of the two active faults, the positive coseismic CFS is ~0.12-0.26 bar on the Xiaojiang fault, and ~0.24-0.52 bar on the Red River fault at 7-km depth. Relaxation of viscoelastic deformation of the lower crust and upper mantle increases the positive CFS to ~0.20-0.6 bar on the Xiaojiang fault, and ~0.32-0.84 bar on the Red River fault at the same depth after ~37 years. The modeled positive CFS correlates well with distribution of the instrumentally recorded seismicity between 1973 and 2003 around the two faults. This means that the 1970 event is presently increasing the CFS on the two active strike-slip faults. The Red River fault recorded little historic earthquake near the segment aside the 1970 event; along the Xiaojiang fault, more than ~37 strong earthquakes in the last ~16000 years have occurred with an average recurrence interval of M ~7.0 event merely ~200-500 years. The last strong earthquakes on different segments of the Xiaojiang fault are ~170 years ago (e.g. the 1500 M>7, the 1713 M~7, the 1733 M~7.8, and the 1833 M~8 earthquakes). Thus, the increase of CFS as our model shown, associating with the relatively short recurrence interval of strong earthquake should lead us to play a great attention on the potential of strong earthquake in the near future.
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 8111 Continental tectonics: strike-slip and transform
DE: 8164 Stresses: crust and lithosphere
SC: Tectonophysics [T]
MN: 2007 Fall Meeting