The Relationship Between Earthquakes And The Gas Geochemical Anomalies In The Mud Of Wenchuan Earthquake Faults Scientific Drilling Hole

It has been confirmed by a number of earthquake cases that there is ground water after the earthquake. Exploring the relationship between fluid geochemistry and earthquake is beneficial for recognizing the earthquake mechanism and improving the capability of earthquake monitoring, forecasting and early warning.Wenchuan Earthquake faults Scientific Drilling (WFSD) provides a research platform to carry out deep fluid geochemistry. WFSD-1 completly recorded the aftershock data and drilling fluid data from November 2008 to July 2009 and got through the main earthquake fault plane. It has some scientific significance.The article was based on the 180-1201m deep underground fluid concentration of gas components, collected WFSD-1 drilled within the fault zone during the aftershocks of 3.5 or above directory information, to study the relationship between the gas composition of subsurface fluid anomalies and aftershocks.In this article, Ar, CO2, CH4, H2, He, N2, O2 and other fluid geochemical profiles was found within the drilling hole of the earthquake fault zone. In 180-1205m deep hole there were many gas abnormalities from underground fluid.To conduct the analysis of the gas composition data flow, the concentration by time and Differential analysis in WFSD-1 hole statistically. In the process of the factors analysis, the accuracy of the factor scores of the of abnormalities indicating aftershocks is 75%. Derived from the statistical analysis, there may exist correspondence between the gas composition of subsurface fluid anomaly and seismic activity in the region. Anomalies generally occur a few days before the earthquake, and continued days after the earthquake, presented in different gas components are not the same exception rule, and the number of abnormal increases with epicentral distance decreased. The change of He, CH4, and CO2 concentration on earthquake component capacity were obviously better than the change of Ar, N2, O2 concentration. He / Ar ratio and N2/O2 mostly showed positive anomalies, Ar/N2 and O2/Ar was opposite to the state. It showed that the relationship of the crustal fluid movement and earthquake activity is actually associated.The anomalies of all the gas components of subsurface fluid in an earthquake was divided into three categories: Abnormal fluid gas group is showed before and after the earthquake CO2, H2, He mass is abnormal, O2, Ar, CH4 negative anomaly; more abnormal peaks is showed CO2, H2, CH4, He is abnormal, O2, Ar negative anomaly; Single peak anomaly is showed CO2, H2, CH4, He is abnormal, O2, Ar negative anomaly.The results showed the relationship between underground fluid and tectonic activity is closed. There are fissures, fracture surfaces, faults in rocks in the place of Ground water significantly in office. The sources of underground fluid is variety. Ratio and related information from N2/Ar that, in the study area are mostly underground fluid precipitation, there may be some of the causes of deep sources. From the ratio of N2/Ar and related information, in the study area are mostly underground fluid precipitation, there may be some of the causes of deep sources.