2017米林M6.9地震序列监测及南迦巴瓦地震活动性研究

南迦巴瓦地震台网完整地记录了米林M6.9地震发生的全过程.本文利用南迦巴瓦地震台网的连续波形数据对米林地震序列进行了研究.南迦巴瓦台网的定位结果显示,米林主震位于29.89°N,95.04°E,震源深度为16.7km,余震序列呈NW向展布,分布在南迦巴瓦峰和加拉白垒峰连线的东北部靠近帕隆—旁辛断裂.经计算,本次地震的h值为1.26,b值为0.84,综合序列衰减情况分析,本次地震属于主震—余震型地震.米林地震前,南迦巴瓦峰地区地震活动表现出明显的时间不均匀性,自研究区1992年ML6.2地震以来,研究区每12年左右发生一次ML6.0级以上地震,2017年至米林地震前,研究区6月前与6月后的地震活动差异很大,6月后的地震活动在频度上要明显强于6月前.空间分布上,米林地震震中附近为研究区地震活动性最强的区域,属于雅鲁藏布江断裂和帕隆—旁辛断裂交汇区域.

2017 Mainling M6.9 earthquake sequences monitored and Namche Barwa seismicity analysis

Namche Barwa earthquake network recorded the whole process of Mainling M6.9 earthquake. Using the continuous waveform data recorded by Namche Barwa earthquake network, this paper analyzed Mainling earthquake sequence. The location results of Namche Barwa earthquake network show that the mainshock is located at 29.86°N, 95.05°E and the focal depth is 16.7 km. The aftershock sequences are distributed in the direction of NW, and in the NE region of Namche Barwa and Gala Peri line, near Palong-Punxin fault. After calculation, the h value of this earthquake sequences is 1.26, b value is 0.84. The comprehensive sequence attenuation analysis shows this earthquake belongs to the main shock-aftershock type. Seismic activity in Namche Barwa shows obvious time inhomogeneity before Mainling earthquake. After M_L6.2 earthquake in 1992, beyond M_L6.0 earthquake happened every 12 years or so. Before 2017 to Mainling earthquake, seismicity is different before and after June, and the seismic activity is obviously stronger after June than that before June. For the spatial distribution of earthquakes, the area with the strongest seismicity is near the epicenter of the Mainling earthquake in study area, which belongs to the intersection area of the Yarlung Zangbo river fault and Palong-Punxin fault.