Gravity Changes before the Lushan, Sichuan, MS7.0 Earthquake of 2013
详细信息
- 责任者：Zhu Yiqing (Second Crust Monitoring and Application Center ; CEA ; Xi’an 710054 ; China) ; Wen Xueze
- 刊名：Chinese Journal of Geophysics
- 出版年：2013
- 卷期：56(6)
- 关键词：重力异常 ; gravity anomaly ; 地震前兆 ; precursor ; 四川 ; Sichuan Province
- 页码：p.1887-1894
- 图表：3 illus., 1 table, 17 refs.
- 分类号：0500
- issnNo：ISSN0001-5733
- isbnNo：CN11-2074/P
摘要
Using the observation data of relative gravity measurements in western Sichuan region from 2010 to 2012, we have systematically analyzed the spatial-temporal variation of the regional gravity field and their relation to the occurrence of the Ms=7.0 Lushan earthquake on April 20, 2013. Our research mainly shows that: (1) Spatially the anomaly change of the regional gravity field is closely related to both the southern segment of the NE-trending Longmenshan fault zone and the NNW-trending Markang fault, suggesting that the active tectonic action or deformation happened along the two fault zones (or segments) during 2010 to 2012, which would have induced the variation in the ground gravity observation. (2) Before the Ms=7.0 Lushan earthquake, regional gravity anomaly appeared in the whole study region and local gravity anomalies at and near the potential source area. Among the region and the areas with gravity anomalies, the anomaly variations near Baoxing, Tianquan, Kangding, Luding and Shimian were up to and over 100×10-8m·s-2 , apparently reflecting an enhancement of tectonic or stress′s action in the study region and at and near the potential source area, that could be related to the preparation and occurrence of the earthquake. (3) The dynamic evolution patterns of the regional gravity changes and those patterns of cumulated gravity variations suggest that significant anomalies of gravity variations in the relative gravity measurements appeared indeed in the last 2 to 3 years in the preparation of the Ms=7.0 Lushan earthquake, and such anomalies can be regarded as one of the medium-term precursory of the earthquake. In a certain degree, the first author of this paper and others once made a medium-term forecast before the Lushan earthquake, especially made a forecast for the locality of the earthquake based on the anomaly gravity variations. The case studied in this article demonstrates again that through relative gravity survey people can catch anomalous gravity variation that would be related to the process of earthquake preparation, especially to those anomaly variations appearing in the last stage of the process. Therefore, relative gravity survey has unique advantages in the medium- to long-term earthquake forecast, especially for forecasting localities of potential earthquakes.