使用宽频带地震记录研究2017年6月24日茂县新磨滑坡的动力学过程

Dynamic processes of the 24 June 2017 Xinmo landslide in Maoxian revealed by broadband seismic records

北京时间2017年6月24日5时39分左右,四川省茂县叠溪镇新磨村发生大型岩质滑坡.体积约4.3×106 m3的巨型岩体从山顶脱落,顺坡滑行约2.6km后破碎沉积;碎屑物掩埋了整个新磨村,造成了巨大的人员伤亡和财产损失.本文使用来自滑坡周围的10个地震台站的宽频带观测资料的长周期信号反演了这次滑坡的受力时间函数;同时使用逐步细化的格点搜索方法得到了滑坡的位置,与其真实位置一致;根据反演的受力时间函数计算了滑坡过程中滑体的运动学参数,得到的滑体运动轨迹与实际路径吻合.综合分析地震信号、受力时间函数和运动学参数表明,本次滑坡主运动的持续时间约为79s;脱落岩体在5∶38∶50.2启动后持续加速,在5∶39∶37.2达到速度峰值,约为52.1m·s-1;这段时间内岩体没有明显的破碎;之后,岩体开始铲刮并裹挟古滑坡造成的碎屑沉积物,自身也开始破碎解体,总体开始减速运动,直到5∶40∶9.2主运动停止;此后,小规模的碎屑散落又持续了约10s的时间.

A catastrophic landslide struck the Xinmo Village in Maoxian County,Sichuan Province,China,at approximately 5∶39 a.m.on 24 June 2017(Beijing Time,UTC+8).About 4.3 million m 3 of rock detached from the crest of the mountain,entrained a large amount of pre-existing deposits,and destroyed the whole village after sliding about 2.6 km along the slope,resulting in serious casualties and property losses.We performed a waveform inversion of the long-period seismic signals extracted from 10 broadband seismic stations around the event to obtain its force time history.The location of this event was also simultaneously acquired using a stepwise refined grid search approach,with a negligible error.We calculated kinetic parameters of the sliding material from the inverted force time history and the deduced runout trajectories were consistent with the morphology.Combined analysis of the seismic signals,force time history,and kinetic parameters revealed that major movement of the landslide lasted approximately 79 s.A large intact rock volume detached at 5∶38∶50.2 and started accelerating afterward,until it reached its peak velocity of 52.1 m·s^-1 at 5∶39∶37.2.No significant fragmentation of the rock could be observed during this time period.Subsequently,the sliding rock mobilized and entrained a large amount of debris of an old landslide deposit along the path and fragmented in the same time.The sliding material started decelerating and finally stopped at 5∶40∶9.2.Small scale scattering of debris lasted for around 10 more seconds after the stop of the major movement.