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

2015 年 M7.8 廓尔喀（尼泊尔）地震引起的震前和震后形变的空间大地测量观测和建模

• 批准号: 1547516
• 负责人: Yuri Fialko
• 金额: $ 19.4万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1547516&HistoricalAwards=false
• 关键词: Space; geodetic; observations; modeling; co

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.

2015年发生的7.8级廓尔喀地震（尼泊尔）是西藏南缘近80年来最大的地震。我们将使用表面变形的精确测量来研究地震破裂以及地震后地壳的缓慢松弛。这些测量结果将引发关于西藏下地壳和上地幔岩石的机械特性和强度的长期争论。我们将比较和对比 2015 年廓尔喀地震观测到的变形与该地区其他大型事件的观测结果，特别是 2005 年克什米尔（巴基斯坦）地震。这将有助于更好地了解尼泊尔及周边地区的地震危害。最近启动的干涉合成孔径雷达 (InSAR) 任务（例如 ALOS-2 和 Sentinel-1）对 2015 年廓尔喀地震进行了很好的成像。新运行卫星的重访时间短、覆盖范围广，将能够以前所未有的细节测量重大浅冲地震造成的震后变形。我们将使用来自不同视线的同震雷达干涉图来推导 2015 年廓尔喀地震的良好约束有限滑移模型。由于地震震中区的特点是地势变化很大，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根据地震层析成像数据推断的地壳 3D 弹性结构。 我们将处理和分析震区长达两年的丰富雷达采集数据，生成震后形变的时间序列，并结合现有的 InSAR 和 GPS 数据来研究震后弛豫机制。在该项目的支持下产生的数据和建模结果将提供给更广泛的研究界。