Spatio-temporal variations of seismicity and coupling in the Himalaya

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。横跨喜马拉雅的大地测量变形主要反映了喜马拉雅主逆冲断层从地表到深度约15-20km的锁定。局部地震监测显示，封闭性断裂带下倾边缘附近的应力聚集可能是导致聚集性地震活动的主要原因。但大地应变和地震活动性的分布呈现横向变化，这表明大地应变和地震活动性都表现出强烈的季节性变化。这些变化可能是由陆地储水量的变化引起的，主要是在恒河平原，但也可能提倡其他原因。利用尼泊尔和西藏南部的连续GPS （Continuous GPS）数据和尼泊尔国家地震台网记录的地震活动数据，分析尼泊尔喜马拉雅地区大地应变和地震活动的空间格局和时间演变。该项目的主要目标是：(1)确定喜马拉雅主逆冲（MHT）的锁定模式；(2)评估地震间应变积累与地震活动性之间的关系；(3)确定应变时间变化的原因；(4)分析地震活动性与应变率之间的关系，并得出地震成核的意义。该项目将有助于限制应力积累的时空模式，这为尼泊尔喜马拉雅地区未来的地震做准备。它将促进我们对物理参数的理解，这些物理参数决定了断层是稳定地蠕动还是具有产生重复地震滑动事件的粘滑运动。它还将促进我们对地震成核的理解。该项目将提供有关尼泊尔和印度北部地震灾害的重要信息。实际上，喜马拉雅地区大地震的频率主要取决于震间期滑动缺陷积累的速度。此外，滑移亏缺的空间格局可能是不均匀的，并可能影响大型地震破裂，正如我们对许多俯冲带所推断的那样。这个项目将解决地震构造学中最具挑战性的问题：为什么一个特定的断层部分会蠕动或产生地震？地震活动率与震间应变积累和其他应力波动源（潮汐、雪荷载、陆地蓄水）有何关系？最后，该项目将促进国际科学合作，并将构成博士研究项目的核心。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Geodetic deformation across the Himalaya reflects primarily locking of the Main Himalayan Thrust (MHT) fault from the surface to a depth of about 15-20km. Local seismic monitoring has revealed clustered seismicity that is probably driven by stress accumulation near the downdip edge of the locked fault zone. The pattern of geodetic strain and the distribution of seismicity show however lateral variations which could reveal heterogeneous stress build up on the Also both geodetic strain and seismicity show strong seasonal variations. These may be induced by landwater storage variations, mostly in the Gangetic plain, but other causes may also be advocated. We therefore offer to analyze the spatial pattern and temporal evolution of geodetic strain and seismicity in the Nepal Himalaya using data from Continuous GPS (CGPS) from Nepal and southern Tibet, and seismicity recorded by the National Seismic Network of Nepal. The main objectives of this project are to(1) determine the pattern of locking on the Main Himalayan Thrust (MHT),(2) assess the relationship between interseismic strain build up and seismicity,(3) determine the cause of temporal changes of strain,(4) analyze the relationship between seismicity and strain rates and derive implications for earthquake nucleation.The project will help constrain the spatio-temporal pattern of stress build up that is preparing future earthquakes in the Nepal Himalaya. It will advance our understanding of the physical parameters that determine whether a fault creeps steadily or has a stick-slip motion producing repeating seismic slip events. It will also advance our understanding of earthquake nucleation.The project will contribute important information regarding seismic hazard in Nepal and northern India. Indeed, the frequency of large earthquakes in the Himalaya depends critically on the rate at which deficit of slip accumulates in the interseismic period. Also the spatial pattern of deficit of slip is probably heterogeneous and might influence large earthquake ruptures as has been inferred for a number of subduction zones.This project will address most challenging questions in seismotectonics: why does a particular fault portion creeps or produces earthquakes? How does seismicity rate relates to interseismic strain buildup and to other sources of stress fluctuations (earth tides, snow loading, landwater storage.) Finally, the project will foster international scientific collaboration and will constitute the core of a PhD research project.