GPS measurements from 10 new permanent sites installed in Himachal, NW Himalaya are analysed with the primary objective to decipher the seasonal crustal deformation characteristics, its origins and hydrological implications. Additionally, we focus on the seismic hazard implications of the seasonal transients as well as of the long-term secular motion of GPS sites. Our findings suggest that the global hydrological loading models can relatively well explain the temporal surface displacements resulting from the monsoon rainfall in the Indo-Gangetic plains (IGP) but poorly account for the winter snowfall in Higher Himalaya. The approximately elliptical horizontal seasonal motion of GPS sites seems to be controlled by the spatio-temporal variations in the monsoonal hydrological load over the IGP. The hydrological process derived from the GPS data suggests slow and steady recovery in the water storage in Himachal Himalaya. The more intriguing phenomena is reflected in the unusually high seasonal site uplift and the yearlong (mid-2020 – mid-2021) plunge in the water storage corresponding to the time-period of COVID-19 lockdown phases, which could be speculated as its indirect impact on the crustal deformation history. The seasonal strain analysis revealed significant spatial heterogeneity. The arc-normal and arc-parallel seasonal strain resulting from differential seasonal motion between GPS sites seems to be primarily localized in the vicinity of locking transition zone, while the locked segment is being largely translated without experiencing significant strain. The localized seasonal strain showed positive correlation with the background seismicity rate suggesting possible modulation of the earthquake nucleation process. The regional seismic hazard assessment suggests susceptibility to a future great earthquake of ∼Mw8.4. The additional observed equivalency between the updated strain budget (∼9.3 m) and the previously reported co-seismic displacement (∼9.3 m) during the last great earthquake around ∼1400–1500 CE, suggests a recurrence interval of ∼600 years for great earthquake events in Himachal Himalaya with significant reliability.

中文翻译：

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来自新 cGPS 测量的喜马拉雅西北喜马偕尔邦的异质季节性变形和应变收支：水文和地震灾害影响


分析了位于喜马拉雅山西北部喜马偕尔邦的 10 个新永久地点的 GPS 测量数据，主要目的是破译季节性地壳变形特征、其起源和水文影响。此外，我们关注季节性瞬变以及 GPS 站点的长期运动对地震危险的影响。我们的研究结果表明，全球水文载荷模型可以相对较好地解释印度恒河平原 （IGP） 季风降雨导致的时间表面位移，但无法很好地解释喜马拉雅高原的冬季降雪。GPS 站点的近似椭圆形水平季节性运动似乎受到 IGP 上季风水文负荷的时空变化的控制。从 GPS 数据得出的水文过程表明，喜马偕尔喜马拉雅山的蓄水量缓慢而稳定地恢复。更有趣的现象反映在异常高的季节性场地隆起和与 COVID-19 封锁阶段的时间段相对应的全年（2020 年中期 - 2021 年年中）储水量暴跌，这可以推测为它对地壳变形历史的间接影响。季节性应变分析揭示了显著的空间异质性。GPS 站点之间季节性运动差异引起的弧法向和弧平行季节性应变似乎主要局限于锁定过渡区附近，而锁定段在很大程度上被平移而没有经历显着应变。局部季节应变与背景地震率呈正相关，提示地震成核过程可能受到调节。 区域地震危险性评估表明，未来 ∼Mw8.4 大地震的敏感性。在公元 1400-1500 年左右的最后一次大地震期间，更新的应变收支 （∼9.3 m） 和先前报告的同震位移 （∼9.3 m） 之间观察到的额外等效性表明，喜马偕尔喜马拉雅大地震事件的重现间隔为 ∼600 年，具有很高的可靠性。