GPS Inversion of Kinematic Model of the Main Boundaries of the Rhombus Block in Sichuan and Yunnan

Abstract

Based on GPS observation between 1991 and 1999 in Sichuan and Yunnan, we adopt the robust Baye's least squares estimation and multi‐fault dislocation models to analyze the quantitative kinematics models of the main boundaries of the rhombus block in Sichuan and Yunnan. The geodetic inversion suggests that the left‐lateral strike slip rates of the Xianshuihe fault zone and the Anninghe fault zone in Sichuan are about 30mm/a with overthrust faulting at rates of roughly 9 and 11mm/a respectively; in Yunnan, the right‐lateral strike slip rate of the Red River (Honghe) fault zone is 10mm/a with a normal faulting of 16 mm/a; and the left‐lateral strike slip rates of the Chenghai fault zone and the Heqing‐Eryuan fault zone are about 11 and 13 mm/a with normal faulting at rates of about 24 and 16mm/a separately. If all displacements along these faults were accommodated by elastic stress and strain, thus the accumulated seismic energy on each fault would be sufficient to produce a moderate earthquake with Ms ~6 each year. According to above results, the horizontal displacement and strain field caused by the main fault movement were simulated and showed the interaction among boundary faults.

GPS-constrained inversion of present-day slip rates along major faults of the Sichuan-Yunnan region, China

“…Sun et al [4] estimated the shear strain rate across the fault zone as 10.9 mm/a through seismic moment inversion. Our inversion results reveal that the Xianshuihe fault slips left-laterally at a rate of 8.9-17.1 mm/a, and the slip rate increases first and then decreases from NW to SE, which is consistent with but slightly higher than previous results [2][3][4][5][8][9][10]14,17,35,36] . Significant extensions appear across the SE section of the Garzê-Yushu fault and the Garzê-Luhuo section of the Xianshuihe fault, possibly associated with a pull-apart basin created by a right step between these two left-slip faults.…”

“…Shen et al [8] used GPS data and inverted for the slip rates of main faults in the Sichuan-Yunnan region employing a multi-fault dislocation model. Shen et al [36] calculated the slip rates of major faults from GPS velocity profiles based on a rigid block motion model.…”

“…The NE trending faults include the Longmenshan and Lijiang-Xiaojinhe faults. Plenty of work has been done in the past about regional geology and deformation [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] , resulting in abundant information for our model setup and testing of the modeling results.…”

“…In recent years GPS techniques have gained rapid developments and have been applied repeatedly in studies on crustal deformation in the Sichuan-Yunnan region [8,[32][33][34][35][36][37] . Shen et al [8] used GPS data and inverted for the slip rates of main faults in the Sichuan-Yunnan region employing a multi-fault dislocation model.…”

Late Quaternary surface deformation and rupture behavior of strong earthquake on the segment north of Mianning of the Anninghe fault

“…The studies on the Late Quaternary deformation and recurrence pattern of strong earthquake of western Sichuan and the Anninghe fault have been carried out almost all the time in the past tens of years and a series of research results, especially on the Anninghe fault, have been gained [3][4][5][6][7][8][9][10][11][12] e.g. the discussions on the tectonic deformation pattern and the temporal-spatial distribution of strong earthquake in the western Sichuan region, the geometry, Late Quaternary activity and segmentation of the Anninghe fault, as well as the paleoearthquakes at certain places.…”