STRAIN ACCUMULATION AND RELEASE IN THE HIMALAYA FROM ALOS-2 INSAR ANALYSIS

We study the active Himalayan deformation via examining the interseismic, coseismic, and postseismic phases, exploring the strain on the Main Himalayan Thrust due to Indian and Eurasian Plate convergence. We examine postseismic deformations resulting from the 2015 M7.8 Gorkha Earthquake, employing InSAR data, ALOS-2 L-band, from the JAXA ALOS-2 SAR satellite. InSAR in the Himalayas is challenging due to the extreme topographic relief, steep slopes, vegetation and snow cover, and L-band is an advantage. We focus on the phase unwrapping, topographic, tropospheric, and ionospheric corrections to improve the InSAR time-series. The final interseismic results provide information on the evolution of the strain field. Initial results from the 2015-2019 Gorkha postseismic analysis are consistent with afterslip down-dip from the 2015 rupture and absence of afterslip on shallower megathrust. This approach sets the stage for future analyses of data from the forthcoming NISAR mission, with enhanced ionospheric and tropospheric corrections.

本研究围绕喜马拉雅活动形变展开，通过解析震间期、同震期与震后期三个阶段，探究印度板块与欧亚板块汇聚作用下主喜马拉雅逆冲带（Main Himalayan Thrust）所承受的应变。本研究采用日本宇宙航空研究开发机构（JAXA）ALOS-2合成孔径雷达卫星获取的L波段合成孔径雷达干涉测量（InSAR）数据，针对2015年M7.8级廓尔喀地震引发的震后形变展开分析。由于喜马拉雅地区存在极端地形起伏、陡峭坡地、植被覆盖与积雪覆盖，该区域的InSAR数据处理颇具挑战，而L波段恰好具备独特优势。本研究聚焦相位解缠、地形校正、对流层校正与电离层校正，以优化InSAR时间序列分析结果。最终得到的震间期分析结果，可为应变场的演化过程提供参考依据。2015至2019年廓尔喀地震震后分析的初步结果，与“2015年地震破裂带下倾方向存在余滑、浅部巨型逆冲断层带无余滑”的结论一致。本研究采用的分析方法，可为未来针对即将发射的NISAR任务所获数据开展的分析工作奠定基础，该任务将具备增强型电离层与对流层校正能力。