1 State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
2 China Earthquake Networks Center, Beijing 100045, China;
3 CEA Key Laboratory of Earthquake Prediction, Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China
Abstract：In order to analyze 3-dimensional movement and deformation characteristics and seismic risk of the Xianshuihe fault zone, we inverted for dynamic fault locking and slip deficit rate of the fault using the GPS horizontal velocity field of 1999-2007 and 2013-2017 in Sichuan-Yunnan region, and calculated annual vertical change rate to analyze the vertical deformation characteristics of the fault using the cross-fault leveling data during 1980-2017 locating on the Xianshuihe fault. The GPS inversion results indicate that in 1999-2007, the southeastern segment of the fault is tightly locked, the middle segment is less locked, and the northwestern segment is basically in creeping state. In 2013-2017, the southeastern segment of the fault is obviously weekly locked, in which only a patch between Daofu-Bamei is locked, and the northwestern segment is still mostly in creeping state, in which only a patch at southeastern Luhuo is slightly locked from surface to 10km depth. The cross-fault leveling data show that annual vertical change rate of the Zhuwo, Gelou, Xuxu and Goupu sites on the northwestern segment is larger, which means vertical movement is relatively active, and annual vertical change rate of the Longdengba, Laoqianning, and Zheduotang sites on the southeastern segment is small, which means the fault is locked, and the vertical movement changes little before and after the Wenchuan earthquake. Combining with the 3-dimensional movement and deformation, seismic activity and Coulomb stress on the Xianshuihe Fault, we consider the seismic risk of the southeastern segment is larger, and the Wenchuan earthquake reduced the far-field sinistral movement and the fault slip deficit rate, which may reduce the stress and strain accumulation rate and relieve the seismic risk of the southeastern segment.
WEN Xue-ze. 2000. Character of rupture segmentation of the Xianshuihe-Anninghe-Zemuhe fault zone, Western Sichuan［J］. Seismology and Geology, 22(3):239-249(in Chinese).
ZHAO Jing, LIU Jie, NIU An-fu, et al. 2014. Study on fault locking characteristic around the Daliangshan sub-block［J］. Seismology and Geology, 36(4):1135-1144(in Chinese).
FANG Ying, JIANG Zai-sen, YANG Yong-lin, et al. 2010. Deformation characteristics of southern segment of Xianshuihe Fault before and after Wenchuan MS8.0 earthquake［J］. Journal of Geodesy and Geodynamics, 30(3):22-26(in Chinese).
LI La-yue, JI Ling-yun, LI Yu-jiang, et al. 2016. Current activity characteristics of Xianshuihe fault zone and its relationship with strong earthquakes based on fault-crossing measurements［J］. Acta Seismologica Sinica, 38(5):739-750(in Chinese).
WANG Li-feng, LIU Jie, ZHAO Jin-gui, et al. 2013. Coseismic slip and post-seismic relaxation of the 2011 M9.0 Tohoku-Oki earthquake and its influence on China mainland［J］. Earthquake, 33(4):238-247(in Chinese).
XUAN Song-bai, SHEN Chong-yang, TAN Hong-bo. 2015. Tectonic implications of images of Bouguer gravity anomaly and its normalized full gradient in Lushan-Kangding area［J］. Chinese Journal of Geophysics, 58(11):4007-4017(in Chinese).
YI Gui-xi, LONG Feng, WEN Xue-ze, et al. 2015. Seismogenic structure of the M6.3 Kangding earthquake sequence on 22 Nov. 2014, Southwestern China［J］. Chinese Journal of Geophysics, 58(4):1205-1219(in Chinese).
Wang H, Wright T J, Biggs J. 2009. Interseismic slip rate of the northwestern Xianshuihe Fault from InSAR data［J］. Geophysical Research Letters, 36(3):L03302.
FANG Ying, ZHANG Jing, JIANG Zai-sen, et al. 2015. Movement characteristics of the northwest segment of the Xianshuihe fault zone derived from cross-fault deformation data［J］. Chinese Journal of Geophysics, 58(5):1645-1653(in Chinese).
HE Mei-xing, FANG Hui, WANG Xu-ben, et al. 2017. Deep conductivity characteristics of the southern Xianshuihe fault zone［J］. Chinese Journal of Geophysics, 60(6):2414-2424(in Chinese).
JIANG Zai-sen, DING Ping, WANG Shuang-xu, et al. 2001. The Geotectonic Deformation Monitoring and Earthquake Prediction in the Western China［M］. Seismological Press, Beijing(in Chinese).
LI Yuan, LIU Xia, LIU Xi-kang, et al. 2016. Activity analysis of faults around Qilianshan before the 2016 Menyuan MS6.4 earthquake［J］. Journal of Geodesy and Geodynamics, 36(4):288-293(in Chinese).
RAN Hong-liu, HE Hong-lin. 2006. Research on the magnitude and recurrence interval of characterized earthquakes with magnitude ≥ 6.7 along the northwestern portion of the Xianshuihe fault zone in western Sichuan, China［J］. Chinese Journal of Geophysics, 49(1):153-161(in Chinese).
SU Qin, YANG Yong-lin, XIANG He-ping. 2012. Seismicity character analysis on the Xianshuihe faults before and after the 2008 Wenchuan M8.0 earthquake［J］. Earthquake Research in Sichuan, (1):24-29(in Chinese).
XIONG Wei, TAN Kai, QIAO Xue-jun, et al. 2015. Tectonic deformation and fault activity of active blocks in Longmenshan and surrounding area after Wenchuan earthquake［J］. Journal of Geodesy and Geodynamics, 35(5):758-763(in Chinese).
XU Jing, SHAO Zhi-gang, MA Hong-sheng, et al. 2013. Evolution of Coulomb stress and stress interaction among strong earthquakes along the Xianshuihe fault zone［J］. Chinese Journal of Geophysics, 56(4):1146-1158(in Chinese).
Savage J C, Gan W J, Svarc J L. 2001. Strain accumulation and rotation in the eastern California shear zone［J］. Journal of Geophysical Research, 106(B10):21995-22007.
YI Gui-xi, WEN Xue-ze, SU You-jin. 2008. Study on the potential strong-earthquake risk for the eastern boundary of the Sichuan-Yunnan active faulted-block, China［J］. Chinese Journal of Geophysics, 51(6):1719-1725(in Chinese).
Papadimitriou E, Wen X Z, Karakostas V, et al. 2004. Earthquake triggering along the Xianshuihe fault zone of western Sichuan, China［J］. Pure and Applied Geophysics, 161(8):1683-1707.
ZHAO Jing, JIANG Zai-sen, NIU An-fu, et al. 2015. Study on dynamic characteristics of fault locking and fault slip deficit in the eastern boundary of the Sichuan-Yunnan rhombic block［J］. Chinese Journal of Geophysics, 58(3):872-885(in Chinese).
ZHAO Jing, JIANG Zai-sen, WU Yan-qiang, et al. 2013. Analysis of reliability and stability of inversion result with negative dislocation model of Defnode［J］. Journal of Geodesy and Geodynamics, 33(1):21-24(in Chinese).
ZHOU Rong-jun, HE Yu-lin, HUANG Zu-zhi, et al. 2001. The slip rate and strong earthquake recurrence interval on the Qianning-Kangding segment of the Xianshuihe fault zone［J］. Acta Seismologica Sinica, 23(3):250-261(in Chinese).
Jiang G Y, Xu X W, Chen G H, et al. 2015. Geodetic imaging of potential seismogenic asperities on the Xianshuihe-Anninghe-Zemuhe fault system, southwest China, with a new 3-D viscoelastic interseismic coupling model［J］. Journal of Geophysical Research:Solid Earth, 120(3):1855-1873.
Wen X Z, Ma S L, Xu X W, et al. 2008. Historical pattern and behavior of earthquake ruptures along the eastern boundary of the Sichuan-Yunnan faulted-block, southwestern China［J］. Physics of the Earth and Planetary Interiors, 168(1-2):16-36.
Zhang J, Wen X Z, Cao J L, et al. 2018. Surface creep and slip-behavior segmentation along the northwestern Xianshuihe fault zone of southwestern China determined from decades of fault-crossing short-baseline and short-level surveys［J］. Tectonophysics, 722:356-372.
McCaffrey R. 2005. Block kinematics of the Pacific-North America plate boundary in the southwestern United States from inversion of GPS, seismological, and geologic data［J］. Journal of Geophysical Research:Solid Earth, 110(B7):B07401.
2018, Vol. 40 
