三峡地区壳幔深部界面重力反演  

Gravity inversion for deep crust-mantle interface in Three Gorges region

作　　者：汪健[1] 申重阳[1] 李辉[1] 孙少安[1] 邢乐林[1] 

机构地区：[1]中国地震局地震研究所地震大地测量重点实验室,中国武汉430071

出　　处：《地震学报》2014年第1期70-83,158,共14页Acta Seismologica Sinica

基　　金：国家自然科学重点基金(40730317);地震行业专项(201008001)资助

摘　　要：为了更精细了解长江三峡地区壳幔深部界面起伏特征,对最新获得的三峡坝区1∶20万完全布格重力异常图与以往三峡地区1∶50万完全布格重力异常图进行拼接,结合人工地震测深、层析成像结果等数据,利用Parker-Oldenburg位场迭代方法对壳幔主要界面进行了反演研究.主要新认识有:巴东—秭归莫霍面深度为42km左右,江汉平原及周边中地壳界面深度为21—25km;深部界面总形态与地表地质构造呈立交桥式结构;三峡大坝处于研究区中地壳最薄处,仅为9km,这可能与黄陵隆起中部存在浅层低密度体有关;三峡地区地震大多发生在本区上地壳内,与壳幔深部界面的起伏变化密切相关,如秭归MS5.1地震发生在莫霍面中地壳界面隆陷梯变最大部位,说明深部作用对区域构造地震活动具有重要影响.Abstract： In order to better understand the fluctuation of deep crust-mantle in- terface in Three Gorges region, we performed the gravity inversion by using Parker-Oldenburg iterative inversion method. During the inversion, we used the existing map of Three Gorges complete Bouguer gravity anomaly （1：500 000） and a new map of Three Gorges dam complete Bouguer gravity anomaly （1 ： 200 000）, as well as results of deep seismic sounding and tomography. The inversion re- sult shows that the Moho depth between Badong and Zigui is about 42 km, the depth of middle crustal interface in Jianghan plain and its surrounding area lies in the range of 21 25 km, and the overall morphology of the deep interface and the surface geology presents an overpass-like structure. The middle crust be neath Three Gorges dam is about 9 km thick, being the thinnest part of the middle crust in this region, which is possibly related to the shallow low-density body in Huangling anticline area. Earthquakes always occur in the upper crust, so there exists close relationship between seismic activity and deep crust-mantle interface fluctuation. For example, the Zigui MsS. 1 earthquake took place in the place where the gradient changes of Moho and middle crustal interface were most significant, indicating that deep structure has important effect on regional seismic activity.

关 键 词：反演 重力异常 深部构造 长江三峡 

分 类 号：P312.1[天文地球—固体地球物理学]