基于有限断层模型的芦山"4·20"7.0级强烈地震强地面运动特征

doi:10.3969/j.issn.0253-4967.2013.02.020

摘要/Abstract

摘要：

基于芦山地震的震源破裂过程反演结果,利用有限断层模型,以芦山地区三维地壳速率结构模型为基础,对芦山 "4·20"7.0级强烈地震引起的强地面运动进行了模拟.对这次地震中由典型盲断层引起的强地面运动数值模拟结果反映了与实际震害相近的分布特征: 断层上盘的宝盛、龙门及芦山以北位于极震区,也是强地面运动的高强度集中区,特别是垂向分量的速度、加速度峰值均在该地区达到了最大值,最能反映地表震害特征的竖向地震加速度在龙门一带达到了350gal,与极震区Ⅸ度的烈度相当,而在芦山以北龙门一带,瞬时竖向位移峰值高达110cm,这些特征与实际震害分布是非常相近的.综合分析认为,这次地震强地面运动表现出了明显的逆冲断层引起的强地面运动的分布特征,同时在强地震动传播过程中,由于高陡峭地形地貌特征及四川盆地内山间盆地的影响,地形地貌和盆地效应对地震波的反射和放大作用明显加强,也是该地区地震破坏强度增大的重要因素.

关键词: 芦山"4·20"7.0级地震, 破裂过程, 有限断层, 强地面运动, 震害分布

Abstract:

Field investigation and damage evaluation of the Lushan M7.0 earthquake have revealed that the seismogenic fault of this earthquake is a typical blind fault with thrust component and there is no distinct surface rupture or deformation zone. The earthquake caused severe damage and failure such as mountain landslide,bedrock collapse,sand liquefaction on near-fault region and tensional fractures. In order to estimate the influence of strong ground motion on damage distribution,based on the inversion of slip distribution and rupture process on the source fault of the Lushan 7.0 earthquake,strong ground motion simulation is carried out with finite-fault model and three-dimension crust model of Lushan area and its adjacent region. In the finite-fault model,the rupture source is characterized as a low-angle fault plane with inhomogeneous slip distribution. The maximum slip on fault plane is up to 150cm. For the three-dimension crust model,deep fault structure,steep terrain and basin have been taken into account and described by different physical parameters. In this paper,the numerical simulation results of strong ground motion about Lushan main earthquake reveal two following major characters. The first is that the distribution characteristics of peak acceleration values,peak velocities and peak displacements on the ground surface shows good consistency with the seismic damage investigation. On the hanging-wall of the causative fault,high intensity of strong ground motion mainly concentrates on Baosheng,Longmen and the northern area of Lushan,which are located within the IX meizoseismal area. Around the area of Longmen town,the maximum acceleration of UD component reaches up to 350gal and the maximum transient displacement is up to 110cm,which are consistent with recordings and investigations. The second conclusion from simulation results is that the strong ground distribution and propagation process are influenced by basin effect and steep terrain. Seismic wave propagated back and forth in intermountain basins,combining with the amplification of thin soil layers,which directly caused and increased the earthquake damage.

Key words: Lushan 7.0 earthquake, rupture process, finite fault, strong ground motion, seismic damage distribution

中图分类号:

P315.2

张冬丽, 黄蓓, 张献兵, 徐锡伟, 郑文俊. 基于有限断层模型的芦山"4·20"7.0级强烈地震强地面运动特征[J]. 地震地质, 2013, 35(2): 423-435.

ZHANG Dong-li, HUANG Bei, ZHANG Xian-bing, XU Xi-wei, ZHENG Wen-jun. STRONG GROUND MOTION DISTRIBUTION AND SIMULATION BASED ON FINITE FAULT MODEL OF LUSHAN 7.0 EARTHQUAKE ON APRIL 20,2013[J]. SEISMOLOGY AND GEOLOGY, 2013, 35(2): 423-435.

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