Space geodetic observations and modeling of co- and post-seismic deformation due to the 2015 M7.8 Gorkha (Nepal) earthquake

2015年尼泊尔发生7.8级地震，是西藏南缘近80年来发生的最大地震。我们将利用地表形变的精确测量来研究地震破裂，以及地震后地球S地壳的缓慢松弛。这些测量将与关于西藏下地壳和上地幔组成的岩石的力学性质和强度的长期争论有关。我们将把观测到的2015年高尔卡地震的形变与该地区其他大地震，特别是2005年克什米尔(巴基斯坦)地震的观测结果进行比较和对比。这将有助于更好地了解尼泊尔及周边地区的地震灾害。最近发射的干涉合成孔径雷达(InSAR)任务，如ALOS-2和Sentinel-1，很好地拍摄到了2015年的Gorkha地震。短时间的重访时间和对新运行卫星的大范围覆盖将使人们能够以前所未有的细节测量由于重大浅部推力地震而产生的震后变形。我们将使用不同视线的同震雷达干涉图来推导出2015年高尔卡地震的约束良好的有限滑移模型。由于地震震中区的特点是高度可变的起伏，我们将通过比较假设弹性半空间的反演结果和明确考虑地形的有限元模型来评估地形的影响。这些模型还将准确地解释从地震层析成像数据推断的地壳的三维弹性结构。我们将处理和分析震区两年来丰富的雷达采集目录，生成震后形变的时间序列，并结合现有的InSAR和GPS数据来研究震后松弛的机制。在该项目的支持下产生的数据和模拟结果将提供给更广泛的研究界。

The 2015 magnitude 7.8 Gorkha (Nepal) earthquake was the largest earthquake at the southern edge of Tibet in the last 80 years. We will use precise measurements of surface deformation to study the earthquake rupture, as well slow relaxation of the Earth?s crust following the earthquake. These measurements will bear on a long-standing debate about mechanical properties and strength of rocks comprising the lower crust and upper mantle beneath Tibet. We will compare and contrast the observed deformation due to the 2015 Gorkha earthquake with observations from other large events in the region, in particular the 2005 Kashmir (Pakistan) earthquake. This will result in better understanding of seismic hazards in Nepal and surrounding areas. The 2015 Gorkha earthquake was well imaged by the recently launched Interferometric Synthetic Aperture Radar (InSAR) missions, such as ALOS-2 and Sentinel-1. Short revisit times and wide-swath coverage of new operating satellites will allow measurements of postseismic deformation due to a major shallow thrust earthquake in unprecedented details. We will use coseismic radar interferograms from different lines of sight to derive a well-constrained finite slip model of the 2015 Gorkha earthquake. Because the earthquake epicentral area is characterized by a highly variable relief, we will evaluate the effects of topography by comparing results of inversions assuming elastic half-space, and finite element models that explicitly account for topography. These models will also accurately account for the 3-D elastic structure of the crust, as inferred from seismic tomography data. We will process and analyze a rich 2-year-long catalog of radar acquisitions in the earthquake area, generate time series of postseismic deformation, and combine available InSAR and GPS data to investigate the mechanisms of postseismic relaxation. Data and modeling results generated under the auspices of this project will be made available to a wider research community.