2017年西藏米林6.9级地震震源参数及其构造意义

The source parameters of the M6.9 Mainling,Tibet earthquake and its tectonic implications

北京时间2017年11月18日06时34分,西藏自治区林芝市米林县发生了M6.9级地震.地震位于印度板块向欧亚板块插入的东北犄角,是喜马拉雅造山带地壳缩短和构造旋转变形最为强烈的部位.本研究利用多种近震和远震台网记录的波形和到时数据,对该地震的震源位置和发震时刻进行重新确定.结果表明,地震震源深度为海平面以下7km±2km(或地表以下10km±2km),经纬度为(29.87°N±0.01°N,95.02°E±0.01°E).结合其他地球物理和地质学资料,我们推测该地震发生在NNW向西兴拉断裂带,南迦巴瓦构造结北东向的逆冲推覆和青藏高原东南向逃逸的侧向挤出是该地震发生的主要构造背景.

On Nov. 18 at 06：34 CST time, an M6.9 earthquake occurred at Mainling prefecture, Nyingchi City, Tibet. This earthquake is located close to the northeastern corner where the Indian plate underthrusts beneath the Eurasian plate. Here the crustal shortening and the tectonically rotated deformation are the strongest with respect to other areas along the whole Himalayan orogenic belt. In this study, we recalculate the location and origin time of this earthquake based on waveforms and arrival times recorded by local and teleseismic networks. The resulting focal depth is 7 km±2 km beneath the sea level （10 km±2 km beneath the surface）, and the epicenter is （29.87°N±0.01°N, 95.02°E±0.01°E）. In combination with other previous geophysical and geological studies, we infer that this earthquake occurred on the NNW-trending Xixingla fault. The major tectonic features for this region are the NE-dipping thrust beneath the Namche Barwa syntaxis combined with the lateral extrusion and southeastern escape beneath the Tibetan plateau.