Study On Well Water Level Response And Mechanism Induced By Earthquake

Earthquakes can cause dynamic changes of groundwater,among which the observation of well water level is the most abundant.In time,it can appear before,during and after earthquakes,and in space,it can appear in the source,epicenter and thousands of kilometers away.Its change forms are various,including instantaneous oscillation or step change,or slow rise or fall.Analysis of these abundant observation phenomena and hydrogeological processes related to earthquake provides a unique way to study the correlation between groundwater regime and tectonic activity.In this paper,the dynamic response and mechanism of well water level change caused by earthquake are studied from the point of view of the change of hydraulic parameters of well aquifer system caused by earthquake.Based on the difference of co-seismic response patterns between well X10 and X11 with the same hydrogeological unit in the same tectonic zone in Xinjiang,the response characteristics and variation mechanism of well water levels in different parts of the same groundwater system to earthquakes are studied.The main contents are as follows:(1)by analyzing the dynamic response characteristics of well water level caused by different earthquakes and the seismic recording ability of well water level,it is explained that the number of coseismic responses recorded by X10 well is far more than that of X11 well;(2)based on the similar occurrence time of four earthquakes(Hutubi Ms6.2 and Solomon Islands Ms7.8 on December 8,2016,Jiuzhaigou,Sichuan on August 8,2017)was explained In this paper,the hydraulic parameters of well aquifer system during seismic wave action and non earthquake period are estimated by using water seismic wave inversion method,pumping test and micro water test method.The mechanism of aquifer permeability change caused by earthquake is discussed.It is considered that the main cause of co-seismic rise of well water level is the aquifer seepage caused by earthquake The increase of permeability.(3)Based on the co-seismic response characteristics of well water level caused by the Xinjiang Urumqi Ms5.2 earthquake,the influence of fault zone on the dynamic change of well water level is discussed from the aspects of co-seismic static strain,seismic energy density,and the response characteristics of well water level to amplitude and phase lag of earth tide The stress state affects the movement state of groundwater flow,resulting in different response characteristics of well water level.To sum up,the mechanism of groundwater dynamic response caused by earthquake is relatively complex,which can not be explained by a single action mechanism,which may be related to various factors such as co-seismic static strain,seismic energy density and borehole conditions.