滑坡的摩擦力与正压力力偶的地震波场模拟  

Simulation of the seismic waves excited by frictional force and normal pressure couple of landslides

作　　者：李文莹 张勇[1] 华思博 许月怡 LI WenYing;ZHANG Yong;HUA SiBo;XU YueYi(School of Earth and Space Sciences,Peking University,Beijing 100871,China)

机构地区：[1]北京大学地球与空间科学学院,北京100871

出　　处：《地球物理学报》2023年第7期2811-2825,共15页Chinese Journal of Geophysics

基　　金：国家自然科学基金(42074058)资助。

摘　　要：滑坡的地震波反演是确定滑坡动力学过程的有效途径.然而,目前的滑坡地震波反演大多基于点源模型,将滑坡面近似为点源,仅考虑滑体作用于滑床的摩擦力及其变化.但实际滑坡过程中,由于重力和滑动距离的存在,滑床还受到一个逐渐增加的正压力力偶作用.为定量探讨这一正压力力偶对滑坡地震波场的贡献,我们基于有限滑坡面模型,分别正演模拟了滑坡过程中摩擦力和正压力力偶的地震波场,得到了正压力力偶地震波场在整个滑坡地震波场中的能量比例及其随距离的变化.研究发现,正压力力偶地震波场具备近场项衰减特征,相较于摩擦力波场随距离衰减更快.正演模拟显示,正压力力偶地震波场在滑坡尺度2~3倍距离范围内较为显著;但在更远距离上,由于其幅度大致随距离的平方衰减,其贡献几可忽略.此外,正压力力偶波场在波形特征上与摩擦力波场也存在明显区别,二者的相对大小与摩擦系数和坡度等参数密切相关.本文模拟分析表明,完整的滑坡近场地震波场应该同时考虑摩擦力和正压力力偶的贡献;滑坡动力学参数反演中,利用近场地震波记录,考虑有限尺度的滑坡面,原则上我们不仅可以确定传统滑坡动力学参数,还有可能确定摩擦系数和流体压力等参数在空间上的变化分布.Seismic inversion is an effective way to study the dynamic processes of landslides.However,current seismic inversions of landslides mostly rely on point-source models,approximating the landslide surface as a point and considering only the frictional force exerted by the sliding body on the sliding bed.In actual landslide processes,the sliding bed is also affected by a gradually increasing normal pressure couple due to gravity and sliding distance.To quantitatively investigate the contribution of this normal pressure couple to the seismic wave field of landslides,we performed forward simulations based on a finite landslide surface model to simulate the seismic wave fields of both the frictional force and the normal pressure couple.We obtained the energy proportions and their variations with distance of the seismic wave field caused by the normal pressure couple compared to the entire landslide seismic wave field.It is found that the seismic wave field resulting from the normal pressure couple exhibits characteristics of near-field attenuation and decays faster with distance compared to the frictional force.Based on the forward simulation results,the seismic wave field generated by the normal pressure couple is significant within a distance range of 2~3 times the size of the landslide.However,at further distances,its contribution can be neglected due to its amplitude decaying roughly proportional to the square of distance.Additionally,the waveforms of the normal pressure couple differ significantly from those of the frictional force,with the relative amplitude closely related to parameters such as the friction coefficient and slope angle of the landslide.The simulation and analysis in this study suggest that both the frictional force and the normal pressure couple should be considered in near-field seismic waves of landslides.By utilizing a finite-source model and incorporating near-field seismic data,it is theoretically possible to determine not only traditional landslide dynamic parameters but also the spatial di

关 键 词：滑坡 摩擦力 正压力力偶 地震波场 

分 类 号：P315[天文地球—地震学]