渭河断陷盆地及邻近地区地震活动的深部背景

利用西安数字地震遥测台网记录的数字地震资料，采用P初动半周期方法，得到了渭河断陷盆地及邻近地区的Q值分布，探讨了该区域地震活动性与地壳内速度分布、Q值分布及地质构造的关系。结果表明：①Q值分布有两个地区存在较强烈地横向不均匀性，其一是淳化、耀县高Q值区和相邻的西安、富平低Q值区，其二是陕晋交界处的韩城高Q值区和相邻的澄城低Q值区，它们都位于不同构造单元交界、差异运动显著、新老地层交错的地区；②历史强震震中主要分布在Q值分布高、低值间的过渡带上；③Q值分布与20km深度P波速度分布有较好地一致性。上述结果表明，该区域的地震活动性有深部构造背景，与区域速度场、介质品质因子分布密切相关。

Seismicity and deep backgrounds of the Weihe fault depression and its adjacent areas

In this paper,by using the seismic data recorded from Xi'an digital telemetry seismic network and the method of half period of first P arrivals ,Q value distribution of Weihe fault depression basin and its adjacent area is determined. The relationship between seismicity and Q value distribution, velocity distribution and geological structures in this region is then discussed. The results show that: (1) there are two strong lateral inhomogeneous regions of Q value distribution, one is Chunhua-Yaoxian region with high Q value and its adjacent Xi'an-Fuping region and Huaxian region with low Q value, the other is Hancheng region on the boundary between Shaanxi and Shanxi Provinces with high Q value and its adjacent Chengcheng region with low Q value. These two regions are located in a region where different tectonic units meet, and differential movement is significant and different rock strata are interceded;(2)the historical strong earthquakes occurred mainly in the transitional belt between the regions with high and low Q values; (3) the distribution of Q value is comparatively consistent with the image of P-wave velocity distribution at depth h=20 km in the studied area.The above results indicate that the seismicity in this region has deep geological background and is closely related to the distribution of Q value and the image of P-wave velocity distribution of the region.