Extraction And Analysis Of Precursory Anomalies Information Of The Deep Groundwater Level Dynamic In North China Plain

The phenomenon of groundwater level change caused by earthquakeis divided into precursory anomalies,Co-seismic and post earthquake response.The precursory anomalies and the Co-seismic have become one of the hot spots in the geological hydrology research.Many mechanisms of Co-seismic groundwater level response and the method of extracting of the groundwater level precursory information are proposed,which play an important role in earthquake monitoring and prediction.However,at this stage,we still can not accurately judge the reliability of the abnormal information of the earthquake groundwater level,and we need to further develop the research on how to accurately judge the abnormal information of the groundwater level.In this Paper,Based on the 27 underground fluid monitoring wells in the North China Plain,collected the groundwater level response data of the underground fluid monitoring wells in the North China Plain for 15 large earthquakes in 2005²015 ten years.From the angle of"multi earthquake and multi well"analyzed the characteristics of the Co-seismic response of the groundwater level in the North China Plain.by the mathematical statistics method,theoretical the volumetric tidal strain,linear regression analysis,tidal analysis,and wavelet transform to quantitatively analyze the amplitude of the the groundwater level of the coseismic,the strength of the groundwater level response of the solid tide and the sensitivity of the volumetric strain of wells,so as to analyze the correlation between the three in the same well.Finally,the sensitive wells are determined in the study area,and extracted and analyzed the abnormal information precursory anomalies in the sensitive wells and non sensitive wells.The following conclusions are obtained:?1?According to the magnitude of the earthquake,the characteristics of the coseismic response of 27 monitoring wells in the North China Plain in 15far field earthquakes are divided into 2 types.There are 10 wells with obvious response to the Ms8.0 earthquake and the largest amplitude to 1m?Zhang Dao Kou well?and 0.9m?Yutian Ji 03 well?,and the response form are mainly equal amplitude oscillation and Impulse type.The 9 wells response form are small amplitude and seismic response are mainly oscillating type,and there are 8wells without the coseismic response.In the Ms7.0^Ms8.0 earthquake,there are 7 wells appeared coseismic response,and the maximum amplitude is 0.1m?Zhang Dao Kou well?.The response form is mainly oscillating and 20 wells without response.?2?the groundwater level with the coseismic response is obvious, the calculated solid tide coefficient is larger,up to 0.092⁰.277m/10^-6,the sensitivity is high,it is 3.39⁴.13m/10^-8.The observation wells water level without the coseismic response is basically not affected by the solid tide,the solid tide coefficient is small,0.0098⁰.0177m/10^-6,and the sensitivity is low,0.02⁰.01m/10^-8,The sensitivity of most wells is 0.It is concluded that the greater the amplitude of the coseismic response,the better the response is to the earth tide,and the higher the sensitivity of the well water level to the seismic strain in the study area.?3?before extracting the precursory anomaly information of the well groundwater level,the comparison analysis of the coseismic response changes of the three kinds of observed frequencies of the groundwater level,the time water level,the hour water level and the daily water level,the result showed that the high frequency observation precision can completely show the oscillatory change caused by the earthquake.The wavelet analysis method is used to extract the information of precursory anomalies as the 2008 Wenchuan Ms8.0 earthquake.Through the above analysis results,we can provide a certain basis for how to choose seismic sensitive wells in the future and how to accurately judge the abnormal information of groundwater level.