Study On The Change Of Water Storage By Ground Gravity In North China Plain

Since 2008,several sets of continuous gravity observation stations have been built or reconstructed in 78 seismic stations by CDSN(China Digital Seismograph Network),Crustal Movement Observation Network of China(CMONOC),China Earthquake Background Field Exploration Project(CEBFEP).The continuous gravity observation network has been connected by using Internet technology.It provides an effective method for seismic monitoring and prediction.It provides an effective method for seismic monitoring and prediction.The law of the water resource have been taken increasingly into account with the national economy rapid development.In order to overcome the relationship among the interaction between the earth layers and monitor the water resources with the continuous gravity observation,More than 4 type of the gravitmeters and 3-4 years datum,GRACE?GLDAS and co-location Groundwater level Data have been analysis each other by Gravity load theory and seasonal variations in Hydrological Influences.At the end,to compensate for the low spatial resolution,about 53 of the ground water wells and 6 periods of the Repeated Gravity Measurement have been analyzed in North China Plain(NCP)and acquired the main components of the water reserves in Region of BeiJin and TianJin.Firstly,In this paper,This paper briefly introduced the basic structure and operational principle of 4 type of the gravimeters,and classified various disturbances occurring in tidal preprocessing with elimination-recovery method,and proposed corrective methods of interference and the processing tools.The characteristics of two tidal analysis method(ETERNA and VAV)are compared by using the actual observation data of spring gravimeter and superconducting gravimeter.It is considered that VAV harmonic analysis method is more suitable for tidal correction of spring gravimeter.And then,in this Paper,the tidal correction method have been introduced.It is shown that,besids air pressure,pole tide,ocean tide,the nonlinear drift of the spring gravimeters is most important influences.We have studied 4 type of nonlinear drift methods in 4 type of gravimeters.When checking the nonlinear drift of the gravimeters by co-located air pressure.The results of PET&gPhone and superconducting gravimeter(SG)were found to be consistent with the theoretical between air pressure and gravity change in 4 different types of instruments.Based on the description of the global terrestrial water model(GLDAS and CPC),GRACE and Ground Water data,the influence of the gravity load theory and Bouguer Plate gravity load is used to verify the above-mentioned nonlinear drift correction.Finally,we have analyzed 6 sets and 4 kinds of continuous gravity observation datum and acquired the method of extracting water load singal from the continuous gravity observation data.This method can be used in North China Plain.In order to explain the difference between ground gravity and satellite gravity,the theory of the gravity load and 3type gravity load method have been introduced.Firstly,The relationship among the Land Surface Model provided by GLDAS,the monthly spherical harmonic coefficients,the water storage of GLDAS by SBH(Special Bureau for Hydrology)and groundwater datums would be analyzed in the Region of Beijin and Zhangjiakou.Compared with hydrologic models in GLDAS,it is shown that,the correlation between the land surface models are more than 90%in Time Domain.However,there are some difference between the spherical harmonic model and LSMs in Space Domain.The groundwater datums is conherence with the spherical harmonic model in Time and Space Domain.So,It is considered than the spherical harmonic model of GLDAS can reflect the time-dependent law of water reserves better than the LSMs in North China Plain.In order to compare the Global Terrestrial water model with GRACE,the method with which coseismic gravity change of the 2011 Mw 9.0 earthquake in Japan can be acquired by GRACE have been verified.And then,The same method have been used to compared the spatial characteristics of the correlation coefficient and standard deviation by the spherical harmonic model of GRACE and GLDAS in North China Plain where is the region of Groundwater Funnel.It is shown that the correlation coefficient is smaller in the region of Groundwater Funnel than of Un-Groundwater Funnel.And standard deviation is larger in the region of Groundwater Funnel than of Un-Groundwater Funnel.So,Compared to the GLDAS,GRACE can be better to reflect the deep material migration such as ground water.And then,according to the Gravity Field Sensitivity Analysis,the magnitude difference between the surface gravity observation and satellite gravity came from the region and deep in the sensitivity region.The ground(basement)gravity load effect can reflect about a radius of 200km,and the satellite gravity load effect can reflect about a radius of 300-350km.At last,base on the method of the water load singal acquired from the continuous gravity observation data and global load water model on the context,the spatial characteristics of the ground water have been studied by the 53 ground water well and 6 periods of the Repeated Gravity Measurement in NCP.the speed and amplitude of the ground water have been analyzed by the wavlet and SSA in the NCP.It is shown that,the decline speed of the ground water is about lm/yr in Beijing-Tianjin region and JiLuyu Junction.This result is same as other research result.And there is the different ground water change speed in and out Beijing area.In Beijing city,the decline of the ground water is not obvious,but in the Beijing downtown,the decline speed of the ground water is lareger than lm/yr.At the same time,compared with the anniversary singal in the ground water well and the continuous gravity observation data by SSA(Singular Spectrum Analysis)and fourier series,it is shown that,the amplitude of 2 order singal in SSA method is same as the anniversary singal in Fourier Series.The amplitude of the anniversary is about 4-8×10-8m/s2 in BeiJin,ZhangJiakou and Taiyuan.In the previous section,the anniversary signal in the ground water and ground gravity observation is interrelated to seasonal variations in Hydrological Influences by the SSA.Then,the GLDAS,GRACE,the Repeated Gravity Measurement and Ground water data have been analyzed with EOF method.It is shown that,the rank 1 of the GLDAS is identical with of the GRACE in NCP.So as to the relationship between the Repeated Gravity Measurement and Ground water data.By gravity load theory,Bouguer Plate gravity theory and the Gravity Field Sensitivity Analysis,the groundwater well data can only reflect the spatial variation about 2-5km around the well.And,restricted with the Repeated Gravity Measurement data,the porosity is identical with the lithology result.There is only ± 10%difference between the restricted result and lithology one.In this paper,we have improve the continuous gravity data process method,proposed the non-linear drift correction method for spring gravimeters and acquired the seasonal variations in hydrological influences from the continuous and repeated gravity measurement by SSA and EOF.Using forward modeling for global terrestrial water model and Grace to compute the water load gravity signal,the anniversary signal of surface gravity observation is identified with of the ground water.The porosity of the ground water in Beijin and Tianjin area was studied by using ground gravity observation data,which will lay the foundation for further study on the change of water reserves in the region by using ground observation data.