Study On Seismic Influence Field Based On Multi-factors

Seismic stations are sparse in most areas of China,and the earthquake impact field is predicted rapidly based on the ground motion map calculated by the attenuation relationship of seismic ground motion.At present,there are some problems,such as inadequate suitability of the attenuation relationship of seismic ground motion in localization and inadequate consideration of site conditions in China.The earthquake impact field often relies only on the in-situ earthquake damage investigation and intensity estimation.Therefore,the study of earthquake impact field based on multi-source data and multi-angle analysis has become an urgent problem to be solved.Based on the research and analysis of satellite remote sensing,station observation and seismic intensity evaluation of historical earthquakes,this paper collects Sentinel 1A/IW images of synthetic aperture radar(SAR)in Jiuzhaigou areas,Digital Elevation Model(DEM)topographic data of Shuttle Radar Topography Mision(SRTM)in kilometer grid,and strong seismic ground motion records of 12 recent earthquakes with magnitude 5 or more in Sichuan area from 2008 to 2017.Based on the observation data from both space and ground aspects,the seismic influence field is studied.Firstly,taking Ms7.0 earthquake occurred in 2017 in the Jiuzhaigou,Sicuan,China as an example,the site condition around the disaster area of the earthquake is classified by using topographic data,and the effects of different site conditions on seismic ground motion are analyzed through acceleration time history,acceleration response spectrum and their attenuation characteristics.Then,using the Peak Ground Acceleration(PGA)recorded by strong motion stations triggered by the 12 strong earthquakes,the attenuation relationship of seismic ground motion in Sichuan region is fitted by stepwise regression and least square method,and the attenuation relationship is established with the attenuation relationship of the Fifth Generation Zoning Map of China's Ground Motion Parameters and Wang Suyun's Attenuation Relation of Ground Motion in Western China.Finally,taking the Jiuzhaigou Ms7.0 earthquake as an example,based on satellite images and ground station observation data such as Sentinel 1A images,aftershocks,peak acceleration records,etc.,the earthquake influence field is determined comprehensively from the aspects of coseismic deformation,aftershock and spatial distribution of PGA,and compared with the intensity distribution map released officially by China Earthquake Administration.The results show that the earthquake influence field is affected by many factors,such as earthquake magnitude,rupture of seismic faults,propagation distance of ground motion,and site conditions.In this paper,topographic slope is used as an alternative index of Vs30(average shear wave velocity within 30 meters below the surface of site)in the absence of measured data of seismic shear wave velocity in shallow layer of the surface.According to the empirical statistical relationship between Vs30 and slope and the site classification method based on Vs30,the sites can be classified rapidly and the effects of different sites on peak acceleration and acceleration response spectrum of ground motion are analyzed.The results show that the soil layer has obvious amplification effect on ground motion.Therefore,the attenuation relationship of PGA considering Vs30 was obtained by stepwise regression analysis.Considering the coseismic deformation range distribution obtained by D-InSAR analysis,aftershock range distribution and PGA spatial distribution of Jiuzhaigou earthquake,the distribution of Jiuzhaigou earthquake influence field is determined,which is compared with the intensity distribution map assessed by seismic field investigation.The results show that the relatively accurate distribution of earthquake influence field can be obtained early by comprehensive evaluation of multiple factors,which can provide important decisionmaking reference for emergency command and rescue after earthquake.