西秦岭北缘断裂带断层气浓度空间分布特征与强震危险性分析

Geochemical Features of Fault Gas on Northern Margin Fault of Xiqinling and Its Seismic Hazard Analysis

以西秦岭北缘断裂带不同段断层气Hg、Rn浓度空间分布特征分析为基础、通过对历史大震背景、现今地震活动影像以及b值空间分布特征的对比分析,从地球化学的角度,对西秦岭北缘断裂带不同段落的活动习性进行深入探讨,并识别出该断裂带潜在大震危险区段。可为未来地震趋势判定及震情跟踪提供重要的基础资料。

The Northern Xiqinling fault zone is located at the northeast edge of the Tibet Plateau,which is one of the largest active faults in northern region of the plateau and the key earthquake hazard area in Gansu province.During the most recent decade,many large earthquakes have occurred in succession near the rim of Bayan Har Block,including the Mani Ms7.9 earthquake on the western border,the KunLun Ms 8.1 earthquake on the northwestern border,the Wenchuan Ms8.0 and Lushan Ms7.0 earthquakes on the eastern border,the Yushu Ms7.1 earthquake on the southern border,and the MinXian Ms6.6 earthquake on the northeast border.The spatial and temporal variation characteristics of these seismic events show that the Bayan Har Block has entered a new period of seismic activity,which has enhanced the earthquake risk of the adjacent areas including the Qaidam and Qilian blocks.Therefore,continued research of seismic hazards and background fields of the Northern Xiqinling fault zone are necessary.In this study,we surveyed the spatial distribution characteristics of fault gas concentration on the Northern Xiqinling fault zone.The hazard area was predicted according to the spatial concentration anomaly values of Hg and Rn soil gas combining with the seismotectonic background and spatiotemporal evolution characteristics of large historical and recent earthquakes.We conclude that the tectonic background of large earthquakes at the F1 and F4 segments of the Western QinLing fault zone includes few small earthquakes,a lengthy period since the most recent large earthquake,and a low gas concentration of Hg and Rn.In comparison,the F3 segment of the Northern Xiqinling fault zone showed frequent small earthquakes,a short period since the most recent large earthquake,and a high gas concentration of Hg and Rn.This research can provide vital background information for earthquake prediction.