渭河断陷及邻近地区震源空间分布规律探讨

选取１０３°～１１３°Ｅ,３１°～３９°Ｎ范围内陕西、山西、河南、湖北、甘肃、宁夏等省（区）共７９个地震观测台站１９８４—１９９３年的观测资料,对于被４个以上台站所记录到的地震,根据其直达横波与纵波的到时差,采用鲍威尔（Ｐｏｗｅｌ）搜索法重新进行了定位,测定了震源深度,共得到２０５１个可定震中的地震的震源深度数据．作出了渭河断陷及邻近地区现代地震的震中分布图、震源空间分布图、震源深度的平均等值线分布图、震源深度的经向剖面图和纬向剖面图．根据这些资料对震源空间分布规律进行了初步探讨．结果表明,渭河断陷及邻近地区震源的空间分布是不均匀的,与该地区大地构造的差异性及地壳速度结构的非均匀性密切相关．

DISCUSSION ON THE REGULARITY OF SPATIAL DISTRIBUTION OF EARTHQUAKE SOURCES IN AND AROUND THE WEIHE DOWNFAULTED BASIN

The 2 051 earthquakes are relocated and their focal depths are determined by using Powell scanning method and time difference of P and S wave from earthquake data observed from 1984 to 1993 at 79 local seismic stations in the zone of 103°~113°E, 31°~39°N in Shaanxi,Shanxi, Henan, Hubei, Gansu and Ningxia provinces.The maps of distribution of present earthquake epicenters,spatial distribution of present earthquake sources,isogram distribution of average focal depths and longitudinal and latitudinal sections of focal depths of present earthquakes in and around the Weihe downfaulted basin are drawn. On the basis of above-mentioned works the regularity of spatial distribution of earthquake sources are studied. The results show that the non-uniform spatial distribution of earthquake sources in and around the Weihe downfaulted basin basically reflects the differences of seismicity level of the region and closely related to the difference of geotectonics and heterogeneity of crustal velocity structure of the region.