Geodetic imaging mega-thrust coupling beneath the Himalaya
Geodetic imaging mega-thrust coupling beneath the Himalaya
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喜马拉雅山下大地测量成像巨型推力耦合
DOI：
10.1016/j.tecto.2018.08.014
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发表时间：
2018
期刊：
影响因子：
2.9
通讯作者：
Gang Chen
中科院分区：
文献类型：
--
作者：
Shuiping Li;Qi Wang;Shaomin Yang;Xuejun Qiao;Zhaosheng Nie;Rong Zou;Kaihua Ding;Ping He;Gang Chen
2015 年廓尔喀地震凸显了了解喜马拉雅地区地震活动的迫切需要，预计喜马拉雅地区的地震活动受青藏高原南缘下方喜马拉雅主断层 (MHT) 上的粘滑行为控制。我们将西藏南部的 GPS 数据与公众可用于对发震断层摩擦特性进行大地测量成像的数据进行整合，旨在更好地了解最大的大陆巨型逆冲断层上的应变累积及其与大地震的关系。耦合模型中修正了三场大地震（1934 年比哈尔邦 Mw8.4、1950 年阿萨姆邦 Mw8.5 和 2005 年克什米尔 Mw7.6）粘弹性松弛造成的震后效应。新模型受到喜马拉雅东部和西部句法之间传播的所有 GPS 速度、水准仪速率和 InSAR 干涉图的约束，证实了先前的发现，即 MHT 完全锁定在地壳最上层 15-20 公里处，在其以下，耦合发生突然下降，在宽 30-50 公里的狭窄过渡区内，系数从 0.8 降至 0.2。一般来说，从GPS速度中去除1934年比哈尔邦和2005年克什米尔地震的震后贡献后，耦合模式变化不大，同时，在去除1950年阿萨姆邦地震引起的扰动后，东喜马拉雅联轴周围的高耦合区域从100km扩大到>140km。断层耦合的空间变化与历史地震震中区吻合较好。在锡金和不丹喜马拉雅山，锁定区比喜马拉雅山沿线的其他地方更宽。不丹喜马拉雅山下过去 300 年积累的应变足以引发 Mw~8.6 的最大地震。
The 2015 Gorkha earthquake highlights the urgent need for understanding seismicity in the Himalaya, which is envisaged to be governed by stick-slip behavior on the Main Himalayan Thrust (MHT) beneath the southern edge of the Tibetan Plateau. We integrate GPS data in southern Tibet with those public available for geodetic imaging of the frictional properties of the seismogenic fault, aiming at a better understanding of the strain buildup on the largest continental mega-thrust and its relation to great earthquakes. The postseismic effects due to viscoelastic relaxation from three large earthquakes (1934 Bihar Mw 8.4, 1950 Assam Mw 8.5 and 2005 Kashmir Mw 7.6) are corrected in the coupling modeling. The new model, constrained by all GPS velocities, spirit leveling rates and InSAR interferograms spread between the eastern and western Himalayan syntaxes confirms previous findings that the MHT is fully locked in the uppermost 15–20 km of crust, below which an abrupt decrease in coupling occurs with coefficients reduced from 0.8 to 0.2 within a narrow transition zone of 30–50 km in width. Generally, the coupling pattern is modified little after removing the postseismic contributions of the 1934 Bihar and 2005 Kashmir earthquakes from GPS velocities, meanwhile, the high-coupling region around the Eastern Himalayan Syntaxis is widened from 100 km to >140 km after removing the perturbation induced by the 1950 Assam earthquake. The spatial variation of fault coupling coincides well with the epicentral areas of historical earthquakes. In the Sikkim and Bhutan Himalaya, the locking zone is wider than elsewhere along the Himalaya. The strain buildup for the past 300 years under the Bhutan Himalaya would be sufficient to power a maximum earthquake of Mw ~8.6.