公元734年天水7级地震对麦积山石窟影响的地震动模拟研究  

Ground Motion Simulation Research on the Impact of the M7.0 Earthquake in Tianshui in 734 AD on the Maijishan Grottoes

作　　者：毛岚 石玉成[1,2] 卢育霞 刘琨[1,3,4] MAO Lan;SHI Yucheng;LU Yuxia;LIU Kun(Lanzhou Institute of Seismology of China Earthquake Administration,Lanzhou 730000,China;Gansu Earthquake Agency,Lanzhou 730000,China;Key Laboratory of Loess Earthquake Engineering of China Earthquake Administration&Gansu Province,Lanzhou 730000,China;Research Center for Conservation of Cultural Relics of Dunhuang,Dunhuang 736200,China)

机构地区：[1]中国地震局兰州地震研究所,甘肃兰州730000 [2]甘肃省地震局,甘肃兰州730000 [3]中国地震局(甘肃省)黄土地震工程重点实验室,甘肃兰州1730000 [4]甘肃省敦煌文物保护研究中心,甘肃敦煌736200

出　　处：《石窟与土遗址保护研究》2024年第3期90-101,共12页Research On The Conservation Of Cave Temples And Earthen Sites

基　　金：国家自然科学基金区域创新发展联合基金项目(U22A20599);中国地震局地震科技星火计划项目(XH24043A);2024陇原青年创新创业人才(2024QNTD51)。

摘　　要：历史上麦积山石窟多次受到地震侵袭,尤其是唐开元二十二年(公元734年)天水地震,对石窟造成了严重破坏。为评估734年天水地震对麦积山石窟造成的影响,设计三种不同发震断层破裂方向(两个单侧破裂和一个双侧破裂),并利用随机有限断层法模拟这些情景下的三分向(两个水平向和一个竖直向)地震动。通过计算加速度峰值(PGA)、速度峰值(PGV)、仪器烈度及麦积山石窟的地面加速度时程、速度时程,得到不同破裂方向下震源模型的地震动响应特征。研究结果表明,当麦积山石窟位于发震断层破裂前方时,持时减小,峰值增大;位于发震断层破裂后方时,持时增加,峰值减小。特别是朝向麦积山石窟破裂的震源模型在南北向对石窟地面产生最大冲击,推测南北方向上峰值滞后且峰值脉冲大的地震动可能导致了麦积山石窟东崖与西崖之间的塌毁。此研究不仅为734年天水地震的重现与麦积山石窟的地震危险性评价提供参考,也为麦积山石窟的地震动力特性分析提供依据。The Maijishan Grottoes site has been impacted by earthquakes many times throughout history,although the Tianshui earthquake in the 22nd year of the Kaiyuan era during the Tang dynasty(734 CE)is notable for the serious damage it caused to the caves at Maijishan.In order to evaluate the impact of the earthquake in 734,this study simulated three different directions of seismic fault fractures(two unilateral fractures and one bilateral fracture),as well as ground motion spreading out in three directions(two horizontal and one vertical)by using stochastic finite-fault ground motion modeling.By calculating the peak acceleration(PGA),peak velocity(PCV),instrument intensity,ground acceleration progression,and velocity progression of the Maijishan Grottoes site,these analyses successfully captured the ground motion response characteristics of the source models under the circumstances of different directional fractures.The results show that when the Maijishan Grottoes site is located in front of the fracture of a seismogenic fault,the duration of the ground motion decreases while the peak value increases;when located behind the fracture,the duration increases and the peak decreases.When applied to the Maijishan Grottoes site,the source model facing the factures was found to exert the greatest impact on the ground of the caves in the north-south direction.It is further speculated that ground motion with peak lag and a large peak pulse in the north-south direction may have led to the collapse between the east cliff and the west cliff of the grottoes,as recorded in 734 following the Tianshui earthquake.This study not only provides reference for simulations of the 734 Tianshui Earthquake and the seismic risk assessment of the Maijishan Grottoes,but also provides evidence for the analysis of the seismic characteristics of the site.

关 键 词：麦积山石窟 734年天水地震 地震动模拟 地震破裂方向 

分 类 号：P315.8[天文地球—地震学] K879.2[天文地球—固体地球物理学]