内蒙古东部地震形势及平均波速比分析

Analysis on seismicity tendency and the mean wave velocity ratio in eastern Inner Mongolia

内蒙古东部地区(41°—51°N,115°—125°E)近几年来地震活动性增强,中强地震比较活跃。2009年,辽蒙交界和牙克石-扎兰屯地区的地震形势更加紧迫。基于内蒙古东部的地震形势分析,根据内蒙古东部地区的台站分布、断裂构造及地震空间分布特点等,划分出4个分区;在2003年到2009年的时段内,筛选出符合计算要求的地震事件482个。根据多台和达法,分别计算各个分区的平均波速比值,通过对波速比曲线进行近均值滑动滤波,分析波速比在中强地震前的变化规律,认为可以把震前波速比异常作为中强地震发生的中短期指标。

The seismicity level and middle-strong earthquake become more active, in eastern part of Inner Mongolia （Latitude 41°--51°, Longitude 115°--125°） in recent years. In 2009, the earthquake situation become more pressing in the boundary area of Liaoning and Inner Mongolia and Yakeshi and Zhalantun area. Based upon the analysise of seismicity tendency, the distribution of seismic stations, faulted structure and the special distribution characteris- tic of earthquakes in eastern Inner Mongolia, the research area is divided into 4 districts. 482 events were selected, in the period from 2003 to 2005, to calculate the mean wave velocity ratio in each district with the method of multiple station arrival summation. Through the slip filtering of wave velocity ratio curve, the variation rule of wave velocity ratio before middle and strong earthquake is analyzed. The result suggests that the anomaly of wave velocity ratio before earthquake may be a prediction index of the moddle and strong earthquakes.