2014年景谷6.6级地震前重力场异常特征研究

Anomalous Characteristics of Gravity Field before the 2014 Jinggu M_(s)6.6 Earthquake

地震的孕育发生过程伴随着构造运动、物质迁移和密度变化,将引起地球重力场变化,流动重力重复观测有可能捕捉到与地震孕育有关的前兆信息,从而为中短期地震预测提供重要依据.对云南地区流动重力观测资料进行整体计算分析,研究了2014年10月7日云南景谷6.6级地震前区域重力场动态演化特征,并利用小波多尺度分解技术对布格重力异常和区域重力场动态变化进行分解,并选取合适的小波基分离得到不同深度场源特征的地壳介质横向不均匀性.结果表明,EGM2008布格重力异常数据和实测重力数据的小波多尺度结果较为一致.对比分析发现,此次景谷地震发生在区域重力场负异常的边缘,由负向正变化的高梯度带附近.基于小波多尺度分解的重力场图像能较清晰地反映2014年景谷6.6级地震孕育、发生过程中震中区域深部物质密度变化引起的异常,为地球构造运动及孕震机理研究提供一定参考.

The process of earthquake incubation is accompanied by tectonic movement,material migration and density changes,which will cause changes in the Earth's gravity field.The mobile gravity observation may capture precursor information related to earthquake incubation,thereby providing important basis for mid-and short-term earthquake prediction.Based on the mobile gravity observation data in Yunnan,the dynamic variation and evolution of regional gravity field before the 2014 Jinggu M_(s)6.6 earthquake on October 7,2014 are studied.The Bouguer gravity anomaly and the dynamic variation of regional gravity field are decomposed by using the wavelet multi-scale decomposition technology,and the crustal medium with different depth field source characteristics is separated by selecting the appropriate wavelet basis.The results show that the wavelet multi-scale results of EGM2008 Bouguer gravity anomaly data are relatively consistent with the measured gravity data.Through comparative analysis,the Jinggu earthquake occurred at the edge of the negative anomaly of the regional gravity field,near the high gradient belt that gravity changes from negative to positive.The gravity field image based on wavelet multi-scale decomposition can clearly reflect the anomaly caused by the change of deep material density in the epicenter area during the preparation and occurrence of Jinggu M6.6 earthquake,which has certain reference research value for the study of tectonic movement and seismogenic mechanism.