短期前兆综合异常方法在青藏高原北部地区的应用——以兴海地震为例

Application of the Short-term Synthetic Anomaly Index of Precursors in Northern Area of Qinghai-Xizang Plateau——Taking the Xinghai Earthquake As the Example

通过对青藏高原北部地区118个定点前兆台项资料的研究,提出了利用前兆台网提取前兆综合异常度指标的方法,包括空间综合度和时间综合度。利用前者来研究青藏高原北部地区强震前短期前兆异常的时空演化特征;利用后者来判定未来中强地震的发震时间。在空间综合异常度的研究中较好地解决了前兆台网分布不均匀引起的异常集中区与震中偏离的问题。作为实例给出了2000年9月12日青海省兴海MS6.6地震前前兆异常的时间和空间综合异常度高值区存在扩散-向震中集中-发震-扩散的过程。

The data from 118 fixed precursor observation stations in north region of Qinghai - Xizang Plateau are selected for research. A method of synthetic anomaly index, including the time and spatial synthetic index, extracting from the data of precursor observation nets, is presented. Using the spatial synthetic index we can research the evolution characteristics of short-term precursor before moderate-strong earthquake in the region, and using the time one we can judge the occurring time for future earthquake. The problem of anomaly area drifting caused by the station not well-distribute is also solved. As the example, the change cause of the time and spatial synthetic anomaly index before Xinhai Ms6.6 earthquake on Sept. 12, 2000, which showed ＂ spreading→consentrating to the epicentre→earthquake→spreading again＂, is introduced.