The geometry of active shortening in the northwest Himalayas and the implications for seismic hazard
The geometry of active shortening in the northwest Himalayas and the implications for seismic hazard
复制标题
喜马拉雅山西北部主动缩短的几何形状及其对地震灾害的影响
DOI：
10.1093/gji/ggac303
复制
发表时间：
2022
影响因子：
2.8
通讯作者：
O'Kane A
中科院分区：
文献类型：
--
作者：
O'Kane A
大型逆冲断层适应了印度和西藏之间沿喜马拉雅山南缘沿着的汇合，并有产生大地震造成广泛破坏的历史。沿着喜马拉雅山的沿着大部分地区，有地貌学证据表明，这些逆冲断层可以在Mw>8的地震中破裂到地表。然而，在喜马拉雅地区的查谟和克什米尔（印度西北部），逆冲断层是盲目的，大规模的褶皱是地表活动变形的唯一表现，这使得很难评估该地区的地震危险性。在本文中，我们使用现场，卫星和地震观测，以确定在查谟和克什米尔断层几何。然后，我们估计从潜在的地震在该地区的地震波场，将产生的模型，如果逆冲断层下查谟和克什米尔断裂地面运动。我们发现，使被锁定的主喜马拉雅冲断层的埋藏浅部破裂的地震可能产生的峰值地面速度比其较深部分的相同震级的地震大3倍以上。我们还模拟地面运动，将导致从逆冲断层的几何形状代表喜马拉雅弧的不同部分。这些模拟表明，即使是看似微小的变化，在浅断层的几何形状可能会导致大的差异，在预期的地面运动，突出的重要性，准确地确定浅层几何逆冲断层沿着山脉的边缘估计地震危险性。
Large thrust faults accommodate the convergence between India and Tibet along the southern margin of the Himalaya and have a history of producing great earthquakes that cause widespread damage. Along most parts of the Himalaya, there is geomorphological evidence that these thrusts can rupture to the surface inMw>8 earthquakes. However, in the Himalayan state of Jammu & Kashmir (NW India), the thrust faults are blind and large-scale folding is the only expression of active deformation at the surface, making it difficult to assess the seismic hazard in this region. In this paper, we use field, satellite, and seismological observations to determine the fault geometry in Jammu & Kashmir. We then estimate the ground motions from potential earthquakes in the region using models of the seismic wavefield that would be generated if the thrust fault beneath Jammu & Kashmir were to rupture. We find that earthquakes that rupture the buried, shallow part of the locked Main Himalayan Thrust could generate peak ground velocities that are >3 times larger than earthquakes of the same magnitude on its deeper portions. We also model the ground motions that would result from the thrust fault geometries representative of different parts of the Himalayan arc. These simulations show that even seemingly minor variations in the shallow fault geometry can lead to large differences in the expected ground motions, highlighting the importance of accurately determining the shallow geometry of thrust faults along the margins of mountain ranges for estimating seismic hazard.