Monitoring the variations of groundwater level in Shaanxi Province based on seismic ambient noise
It is a useful attempt to monitor the variations of groundwater level based on the changes of the seismic wave velocity by using seismic ambient noise.In this paper,we collected continuous records from several seismic stations in the Weihe River and Han River,extracted seismic wave velocity variations by using the auto-correlation functions of seismic ambient noise,and analyzed the response of seismic velocity variations to regional precipitation and groundwater level changes.It was found that:(1)Seismic velocity variations have obvious time-varying characteristics and relates to the regional precipitation processes under certain delays;spatially,the corresponding seismic velocity variations are obvious in high elevation areas due to persistent water level adjustments,while there are relatively small in river valley areas due to stable water level changes.Meanwhile,the north-south spatial difference in overall precipitation in Shaanxi is also reflected in the variational peaks of seismic velocity for different seismic stations,i.e.,the velocity variation for the seismic stations in the Han River basin is slightly higher overall than those in the Wei River basin.(2)Combining the water level and seismic velocity changes given by groundwater and seismic observations,there are differential delays between the groundwater level changes and the seismic wave variations,and especially,the presence of the Ankang reservoir leads to a smaller magnitude and larger time delay in the dv/v variation at the seismic station ANKG than others.
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