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2015年4月25日,在印度板块与欧亚板块交界区的喜马拉雅地震带上发生了尼泊尔MS 8.1级大地震.震前GPS速度场和应变率场显示,喜马拉雅地震带整体表现为15.94±1.82 mm/a的压缩特征,同时还具有分段活动特征.此次地震发生在速度场顺时针旋转和逆时针旋转的分界带,该处最大主压应变率的量值在喜马拉雅地震带并非最大.GPS观测的同震位移场揭示了尼泊尔MS 8.1级地震引起的地壳变形特征,分别有9和6个测站观测到明显的水平向和垂向同震位移,其水平分量的运动方向整体表现为南向运动,位于震中东南侧的3个测站垂直分量表现为上升,其余测站为下降.中国境内距离震中最近的5个测站的垂向同震位移显示,此次地震造成珠穆朗玛峰的沉降量约为4mm.依据GPS观测到的同震位移场,利用非负最小二乘方法反演震源断层面上的滑动分布.反演结果表明最大滑动量为6.84 m,滑动量较大的区域分布在加德满都附近及其以北区域的下方,这可能是造成加德满都地区具有较大破坏的原因之一,该滑动分布模型能够很好地解释GPS观测到的同震位移.利用此滑动分布模型计算的地震矩为8.21×1020 N m,对应的矩震级为MW7.9.
An MS 8.1 MS8 magnitude earthquake occurred in Nepal in the Himalayan seismic zone at the junction of the Indian and Eurasian plates on April 25, 2015. The GPS velocity and strain rate fields before the earthquake showed that the overall Himalayan seismic zone showed an average of 15.94 ± 1.82 mm / a, and also has the characteristics of subdivision activity.The earthquake occurred in the boundary between the clockwise rotation and counterclockwise rotation of the velocity field, where the magnitude of the maximum principal compressive strain rate is not the maximum in the Himalayan seismic zone. The coseismic displacement field revealed by the GPS reveals the crustal deformation characteristics caused by the Ms 8.1 MS Nepal earthquake. There are 9 and 6 stations observing significant horizontal and vertical coseismic displacements, respectively, and the horizontal component of the crustal movement shows overall In the southward movement, the vertical component of the three stations located on the southeast side of the epicenter show a rise and the remaining stations are descending.The vertical coseismic displacements of the five stations nearest to the epicenter in China show that the earthquake caused Everest Of the settlement is about 4mm.According to the co-seismic displacement field observed by GPS, the non-negative least square method is used to invert the slip distribution on the focal fault plane.The inversion results show that the maximum slip is 6.84 m, The large area distributes near Kathmandu and its north area, which may be one of the causes of greater damage in Kathmandu region, which can well explain the observed coseismic displacements by GPS. The seismic moment calculated by the distribution model is 8.21 × 1020 Nm and the corresponding moment magnitude is MW7.9.