Pre- and post-seismic deformation related to the 2015, Mw7.8 Gorkha earthquake, Nepal
Pre- and post-seismic deformation related to the 2015, Mw7.8 Gorkha earthquake, Nepal
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DOI：
10.1016/j.tecto.2016.06.014
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发表时间：
2017-09-13
期刊：
影响因子：
2.9
通讯作者：
Liu-Zeng, Jing
中科院分区：
文献类型：
--
作者：
Gualandi, Adriano;Avouac, Jean-Philippe;Liu-Zeng, Jing
我们分析了2015年4月25日发生在尼泊尔的M（w）7.8 Gorkha地震前后连续记录GPS站的时间序列，该地震破坏了喜马拉雅主冲断层（MHT）。记录显示，由于地表水文，季节变化很大。在对这些变化进行校正之后，覆盖地震前和地震后时期的时间序列没有显示出任何可检测到的瞬时震前位移。相比之下，瞬态震后信号是清晰的。观测到的信号显示出向南的位移与MHT上的后滑一致。使用额外的数据部署后的主震站，我们反转的时间序列的时空演变的MHT上的滑移。这个模型表明余震主要是主震破裂的下倾。另外两个地区表现出明显的后滑：一个更小的破裂区上倾，以及主震和最大余震破裂之间的区域。在主震后第一个类似于7个月的余震释放了[12.8 +/- 0.5] x 10（19）Nm的力矩，相当于同震力矩的17.8 +/- 0.8%。在这段时间内，余震释放的力矩估计为2.98 × 10（19）Nm。因此，在同震偏移校正后，大地测量观测到的震后变形为76.7 +/- 1.0%。后滑的对数时间演化与速率强化型摩擦滑动相一致。根据这一理论，并假设根据该地区的耦合图和20.2 +/- 1.1 mm/yr的长期滑动速率调制长期加载速度，在震后变形完全松弛后，后滑动应释放约34.0 +/- 1.4%的同震力矩。后滑导致MHT较浅部分的负荷，该部分在2015年没有破裂，之后保持锁定。在尼泊尔，Gorkha地震破裂区的上倾和加德满都西部发生进一步大地震的风险仍然很高，MHT一直处于锁定状态，自1505年以来没有发生过大于M（w）7.5的地震。(C)2016由Elsevier B. V.出版
We analyze time series from continuously recording GPS stations in Nepal spanning the pre- and post-seismic period associated to the M(w)7.8 Gorkha earthquake which ruptured the Main Himalayan Thrust (MHT) fault on April 25th, 2015. The records show strong seasonal variations due to surface hydrology. After corrections for these variations, the time series covering the pre- and post-seismic periods do not show any detectable transient pre-seismic displacement. By contrast, a transient post-seismic signal is clear. The observed signal shows southward displacements consistent with afterslip on the MHT. Using additional data from stations deployed after the mainshock, we invert the time series for the spatio-temporal evolution of slip on the MHT. This modelling indicates afterslip dominantly downdip of the mainshock rupture. Two other regions show significant afterslip: a more minor zone updip of the rupture, and a region between the mainshock and the largest aftershock ruptures. Afterslip in the first similar to 7 months after the mainshock released a moment of [12.8 +/- 0.5] x 10(19) Nm which represents 17.8 +/- 0.8% of the co-seismicmoment. The moment released by aftershocks over that period of time is estimated to 2.98 x 10(19) Nm. Geodetically observed post-seismic deformation after co-seismic offset correction was thus 76.7 +/- 1.0% aseismic. The logarithmic time evolution of afterslip is consistent with rate-strengthening frictional sliding. According to this theory, and assuming a long-term loading velocity modulated on the basis of the coupling map of the region and the long term slip rate of 20.2 +/- 1.1 mm/yr, afterslip should release about 34.0 +/- 1.4% of the co-seismic moment after full relaxation of post-seismic deformation. Afterslip contributed to loading the shallower portion of the MHT which did not rupture in 2015 and stayed locked afterwards. The risk for further large earthquakes in Nepal remains high both updip of the rupture area of the Gorkha earthquake and West of Kathmandu where the MHT has remained locked and where no earthquake larger than M(w)7.5 has occurred since 1505. (C) 2016 Published by Elsevier B.V.