摘要
计算了 1 991年～ 1 999年发生在北纬 3 9°0 0′～ 42°0 0′,东经 1 1 2°3 0′～ 1 1 6°0 0′范围内的ML≥ 2 .0级地震的波速比 ,分析了张北 6 .2级地震前后源区与场区波速比的时空变化特征及其差异 ,发现 6 .2级地震前源区和场区波速比在时间分布上都出现较明显的低值异常 :下降—低值—平静—恢复—发震过程。在空间分布上低值异常比较集中和同步。对计算结果进行了 t检验 ,源区与场区波速比的时空变化及 t检验表明 6 .2级地震前源区与场区波速比异常非常明显 ,场区 1 995年开始出现波速比在正负之间比较大的变化后持续低值。 6 .2级地震后源区和场区的波速比计算结果一致 。
The seismic velocity ratio for earthquakes(M L≥2.0)during 1991 to 1999 in the region 112°30′～116°00′E,39°00′～42°00′N is calculated.The variation character in time and space and the differences of the seismic velocity ratios before and after Zhangbei Ms6.2 earthquake in source region and field area are analyzed.The results show that distinct low value anomalies of seismic velocity ratio in time distribution appeared in source region and field area before the event.The course is decline-low value-quietude-recovery-occurrence.The low value anomalies are concentrative and synchronous in spatial distribution.The calculation is tested with T-test.The results indicates that the seismic velocity ratio anomalies in source region and field area are very obvious before Zhangbei Ms6.2 earthquake.The seismic velocity ratio in field area sustained low value after great changes since 1995.The seismic velocity ratio became uniform and its time and space variation also became normal after the event.
出处
《华北地震科学》
2001年第2期14-20,共7页
North China Earthquake Sciences
