广义海原断裂带断层气地球化学特征与地震活动性关系对比研究

Geochemical Characteristics of Fault Gas along Generalized Haiyuan Fault Zone and Its Relation to Earthquakes

根据广义海原断裂带断层气汞、氡浓度现场测量结果,对该断裂带不同段断层气浓度空间分布特征以及整体分布趋势进行深入分析,结合该区历史大震背景、现今地震活动性以及地震时空分布特征及b值空间扫描,深入探讨断层气分布特征与地震活动性之间的关系。研究表明,该断裂带断层气浓度强度分段性明显,与地震活动性存在较好的对应关系。研究结果可为该断裂地震危险性分析提供现今深部流体地球化学活动方面的证据,也为今后地震中长期预报提供重要基础资料。

The eastern section of the North Qilian fault zone lies on the northeastern edge of the Qinghai—Tibet Plateau uplift zone,which consists of the Jinqianghe fault,Laohushan fault,and Maomaoshan fault.The Haiyuan fault,located in the west of the Ordos Block,is a NW trending, large strike-slip fault.It has good continuity with the eastern segment of the North Qilian Moun-tain fault,and both exhibit left-type dislocation.Therefore,the eastern segment of the North Qil-ian Mountain fault and the narrow Haiyuan fault are collectively referred to as the generalized Haiyuan fault zone.Seismic activity is very strong in this area,where many MS≥7.0 earthquakes have occurred over time,such as the famous 1920 Haiyuan MS8.5 earthquake and the 1927 Gulang MS8.0 earthquake.Therefore,the region＇s seismic hazards should be carefully investigated.Based on the measurement results of the mercury and radon concentrations of 10 fault-gas profiles in the generalized Haiyuan fault zone,in this paper,we describe our detailed analysis of the spatial distri-bution characteristics of the mercury and radon concentrations in different segments and their o-verall distribution trend along the fault zone.Combined with the seismotectonic background and spatio-temporal evolution characteristics of large earthquakes,as well as the spatial distribution characteristics of the b-value,we studied the relationship between the spatial distribution charac-teristics of fault gas and the seismic risk of different segments in the generalized Haiyuan fault zone.The results show that the intensity of the fault-gas concentration in the fault zone exhibits obvious segmentation,and is also correlated to some degree with the seismic activity.Based on the above research,we made a pre-j udgment of the potential seismic risk in different segments of the generalized Haiyuan fault zone from the geochemistry perspective.This research can provide vital background information for earthquake prediction in the study area.