| 喜马拉雅主逆冲断层闭锁程度与滑动亏损特征研究 |
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| 引用本文： | 赵静,江在森,牛安福,武艳强,占伟,魏文薪.喜马拉雅主逆冲断层闭锁程度与滑动亏损特征研究[J].武汉大学学报(信息科学版),2017,42(12):1756-1764. |
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| 作者姓名： | 赵静 江在森 牛安福 武艳强 占伟 魏文薪 |
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| 作者单位： | 1.中国地震局地质研究所地震动力学国家重点实验室, 北京, 100029 |
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| 基金项目： | 地震科技星火计划项目XH15049Y国家自然科学基金41330314国家自然科学基金412740082015-度震情跟踪专项工作任务2015010201 |
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| 摘 要： | 基于融合的GPS速度场结果，使用DEFNODE负位错反演程序估算了喜马拉雅主逆冲断层（the main Himalayan thrust，MHT）的闭锁程度和滑动亏损空间分布，并结合剖面结果分析了断层远、近场的运动特征。结果表明，MHT的闭锁深度基本达到18~24 km，断层面闭锁宽度达到102~136 km，两次历史大地震破裂区域之间的未破裂段落和未发生大地震的段落闭锁深度更深，闭锁断层面更宽，2015年尼泊尔Mw7.8大地震就发生在两次大地震破裂区域之间的段落；MHT总滑动亏损速率和垂直断层挤压滑动亏损速率自东向西逐渐减小，平行断层右旋滑动亏损速率则基本上自东向西逐渐增加；MHT 3条剖面拟合结果也反映出其存在很强的闭锁。根据估算的此次Mw7.8地震的复发周期230年和最近500多年发生的大地震分布，认为MHT整条段落尤其是尼泊尔西部与印度接壤处和可能还没有破裂的不丹地区依然有发生8级大地震的危险。
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| 关 键 词： | 尼泊尔地震 速度场融合 MHT 断层闭锁 滑动亏损 |
| 收稿时间： | 2016-05-18 |
Characteristics of Fault Locking and Fault Slip Deficit in the Main Himalaya Thrust Fault |
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| Affiliation: | 1.State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China2.China Earthquake Networks Center, Beijing 100045, China3.CEA Key laboratory of Earthquake Prediction, Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China4.First Crust Monitoring and Application Center, China Earthquake Administration, Tianjin 300180, China |
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| Abstract: | An Mw7.8 earthquake occurred in Nepal on April 25, 2015. The epicenter is (28.147°N, 84.708°E). It occurred as a result of fault thrusting on the main thrust interface between the subducting India plate and the overriding Eurasia plate to the north. The movement and locking of the main Himalaya thrust (MHT)fault and its seismic potential need us to do some further study. We collected 6 sets of GPS horizontal velocity field covering Indian plate, Qinghai-Tibet plateau and adjacent areas, and transformed them to an approximately unified reference frame. Then we used the negative dislocation model of DEFNODE to invert the spatial fault locking and fault slip deficit in the MHT, and analyzed the far-near field movement of the fault combining with the GPS velocity profiles.The results show that the locking depth of the MHT is about 18-24 km, and the locking width of the fault plane reaches 102-136 km. The locking depth is deeper and the locking width of the plane is wider in the fault between two major historical earthquakes rupture area and the fault of no historical earthquakes. The Mw7.8 Nepal Earthquake is located in the area between two major historical earthquakes rupture area where the fault is relatively deeply and tightly locked. The total slip deficit and vertical compressional slip deficit of the MHT gradually reduce from east to west. The vertical compressional slip deficit of the easternmost segment of the fault is about 28.0 mm/a, which gradually reduces in the tightly locked area, and decreases to about 6.4 mm/a at the westernmost segment. The dextral strike-slip of parallel slip deficit changes from 0.4-7.0 mm/a from east to west in Nepal. The three profile model fitting results of the MHT are consistent with the slip deficit of corresponding fault plane, and it is very like the profile results across the middle segment of the Longmenshan fault before the 2008 Wenchuan earthquake, which reflects that the MHT is tightly locked. We estimated that the Mw7.8 earthquake recurrence is about 230 years according to the peak slip and the vertical compressional slip deficit at the epicenter. Because only the 1905 India Kangra 8.0 earthquake, the 1934 Nepal Bihar 8.1 earthquake and this Nepal Mw7.8 earthquake happened for recent 500 years, it is possible that M8 earthquake happens on this fault especially on the border of Nepal and India and possibly unruptured Bhutan. |
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