Significant isostatic imbalance near the seismic gap between the M8.0 Wenchuan and M7.0 Lushan earthquakes  

作　　者：Guangyu Fu Guoqing Zhang 

机构地区：[1]Key Laboratory of Earthquake Prediction, Institute ofEarthquake Science, China Earthquake Administration [2]Key Laboratory of Computational Geodynamics, Chinese Academy of Sciences [3]State Key Laboratory of Geodesy and Earth’s Dynamics

出　　处：《Chinese Science Bulletin》2014年第34期4774-4780,共7页

基　　金：supported by Basic Research Projects of Institute of Earthquake Science,China Earthquake Administration(CEA)(2013IES01013 and 2011IES010103);the East-Asia Earthquake Project(ZRH2013-01);the National Natural Science Foundation of China(41331066);the Open Fund of StateKey Laboratory of Geodesy and Earth’s Dynamics(SKLGED2014-43-E)

摘　　要：A gravity network with 302 observation points has been established in the western Sichuan Foreland Basin(SFB) to explore Bouguer gravity anomalies(BGAs). Our observational results reveal that the BGAs are negative as a whole, with a maximum value of-220 m Gal(10-5m s-2)at the northwest region of the study area. The real Moho depths beneath the SFB revealed by BGA data change smoothly from 39.5 km in the southeast to 43.7 km in the northwest of the monitoring region. However, the isostatic ones deduced from Airy isostatic model and topographical data vary approximately 39.5–42.0 km. The maximum differences of 2.7 km between the real and isostatic Moho depths are found near the seismic gap between the M8.0Wenchuan and M7.0 Lushan earthquakes, where the crust is in the greatest isostatic imbalance of the monitoring region. Analysis of the isostatic state indicates that the deep dynamic environment near the seismic gap between these two earthquakes indicates an M C 7.0 earthquake in the future. This study indicates that we can use isostasy as a potential approach to study the dynamic process of crustalmaterial movement and to analyze regional potential seismic risks.A gravity network with 302 observation points has been established in the western Sichuan Foreland Basin （SFB） to explore Bouguer gravity anomalies （BGAs）. Our observational results reveal that the BGAs are negative as a whole, with a maximum value of -220 mGal （10^-5m s^-2） at the northwest region of the study area. The real Moho depths beneath the SFB revealed by BGA data change smoothly from 39.5 km in the southeast to 43.7 km in the northwest of the monitoring region. However, the isostatic ones deduced from Airy isostatic model and topographical data vary approximately 39.5-42.0 km. The maximum differences of 2.7 km between the real and isostatic Moho depths are found near the seismic gap between the M8.0 Wenchuan and M7.0 Lushan earthquakes, where the crust is in the greatest isostatic imbalance of the monitoring region. Analysis of the isostatic state indicates that the deep dynamic environment near the seismic gap between these two earthquakes indicates an M ≥ 7.0 earthquake in the future. This study indicates that we can use isostasy as a potential approach to study the dynamic process of crustal material movement and to analyze regional potential seismic risks.

关 键 词：地震发生 庐山 汶川 BGA封装 布格重力异常 失调 川西前陆盆地 地壳均衡 

分 类 号：P315[天文地球—地震学]