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.

Key words: the Xianshuihe Fault, fault locking, annual vertical change rate, 3-dimensional deformation characteristics

摘要： 为了综合分析讨论鲜水河断裂带的三维运动与变形动态特征和地震危险性，利用川滇地区1999—2007和2013—2017 2期GPS速度场资料，反演计算了鲜水河断裂带的闭锁程度和平行与垂直断层的滑动亏损速率动态分布；利用布设在鲜水河断裂带附近的1980—2017年跨断层短水准资料，通过计算断层年均变化速率分析了断裂带垂直运动特征。GPS反演结果显示：1999—2007期鲜水河断裂SE段处于强闭锁状态，中段闭锁程度逐渐减弱，到NW段基本为蠕滑状态；2013—2017期鲜水河断裂SE段滑动亏损积累速率明显减弱，只有道孚—八美段之间有一小段闭锁较强，NW段依然大部分为蠕滑状态，只有炉霍SE部一段断层地表至10km深度闭锁稍有增强。水准结果显示：鲜水河断裂NW段侏倭、格篓、虚墟和沟普场地年均垂直变化速率较大，断层垂向活动较为活跃；SE段龙灯坝、老乾宁和折多塘场地年均垂直变化速率很小，断层垂向活动处于闭锁状态；汶川地震后断层垂向活动变化并不明显。综合分析认为鲜水河断裂SE段的地震危险性较高，而汶川地震降低了断层滑动亏损和应力应变能积累速率，可能在一定程度上缓解了鲜水河断裂尤其SE段的地震紧迫性。

关键词: 鲜水河断裂, 断层闭锁程度, 年均垂直变化速率, 三维变形特征