2008年汶川Ms8.0地震前定点形变高频异常特征的研究

High-Frequency Anormaly Characteristics of Fixed-point Deformation before the 2008 Wenchuan M_S8.0 Earthquake

本文以中国大陆西部定点形变观测资料作为研究对象,采用S变换和超限率时频分析法对其进行了处理和分析。研究结果表明:在2008年汶川MS8.0地震前,距离震中600km范围内的定点形变个别台站观测到高频异常,异常持续时间较长;距离震中300km范围的个别台站临震高频异常非常显著;并且不同的定点形变观测手段对高频信号的响应不同,地倾斜测项临震前高频异常形态较地应变测项更为清晰灵敏。同时S变换和超限率两种方法处理结果具有较好的一致性,表明本文提取到的高频异常可信度较高。

In this article,the fixed point deformation data of the west Chinese mainland had been analyzed by the analytical method of S transformation and overrun rate.The results show that abnormal signals with high frequency had been observed by some fixed-point deformation stations in the area of 600 km from the epicenter before the 2008 Wenchuan MS8.0 earthquake and had lasted a longer time.The short-term and impending highfrequency anomalies are obvious in the area 300 km from the epicenter.In addition,the responses to high-frequency signals are not the same for different fixed-point derformation approach.Usually,high-frequency anomaly patterns of ground tilt are more sensitive and clear than crustal strain.Meanwhile,the results of S transformation and overrun rate analyses have good consistency,which indicates the reliablity of the extracted high-frequency anomaly.