Spatiotemporal Evolution Characteristics Of Gravity Field Caused By Tectonic And Non-tectonic Factors Based On GRACE/GRACE-FO Gravity Satellite

At present,the world is faced with many severe environmental changes,such as crustal movement,land water reserves change,sea level rise,glacier melting and so on.These problems are closely related to the migration of surface materials,which will cause the redistribution of the earth's mass and is an important factor leading to the change of the earth's time-varying gravity field.Therefore,an in-depth study of the temporal and spatial distribution of regional surface material migration and the resulting characteristics of the temporal and spatial evolution of the gravity field has important theoretical and practical significance for a deep understanding of the mechanism of regional climate and environmental evolution and the relationship between human activities and the natural environment.With the rapid development of space monitoring technology,especially GRACE(Gravity Recovery and Climate Experiment)and GRACE Follow On(GRACE-FO)gravity satellites have many advantages such as high precision,allweather,continuity,global coverage,etc.,so that they can provide Long-term earth observations and time-varying gravity field models which have become effective technical means for continuous monitoring of regional time-varying gravity information.Based on this,this paper considers from tectonic and non-tectonic factors respectively,and selects two cases of regional surface material migration phenomenon as examples: typical strong earthquake(Chile Mw8.8 earthquake in 2010)and typical groundwater reserves change(North China region).Using the high-precision time-varying gravity field provided by the gravity satellite,the regional mass changes caused by strong earthquakes and changes in groundwater reserves are inversed,and the temporal and spatial differences and evolution characteristics of regional surface material migration caused by the two factors are discussed.The main achievements and innovations are summarized as follows:(1)In view of whether gravity satellites can effectively detect coseismic gravity changes caused by strong earthquakes with Mw<9.0(tectonic factors)and long-term post-earthquake gravity field changes,this paper combines the GRACE and GRACE-FO time-varying gravity field models for the first time to explore the spatio-temporal evolution characteristics of the full-time chain gravitational field of the Chilean Mw8.8 strong earthquake from pre-earthquake,coseismic to post-earthquake,and to verify the advantages of GRACE/GRACE-FO in monitoring the gravity field changes of strong earthquakes with MW8.0 and above,and better reveals the characteristics of the long-term change trend of the gravity field after strong earthquakes,which has important theoretical reference value for deep understanding of the crustal movement after the earthquake and the adjustment of mantle viscoelasticity under the action of plate subduction.(2)Aiming at the problem of susceptibility to stripe errors when using GRACE time-varying gravity field model to invert the surface gravity changes caused by earthquakes,this paper further develops the use of gravity gradients on the basis of the study of coseismic gravity changes of the Chile Mw8.8 earthquake,and verifies it by cross comparison with the theoretical change of gravity gradient acquired by difference method.The results show that the gravity gradient method can greatly suppress the stripe error while retaining more effective signals,which can effectively improve the observation accuracy and sensitivity,and provide a new idea for the use of gravity satellites to detect coseismic gravity field effects.(3)This paper makes full use of the advantages of gravity satellite in detecting the regional time-varying gravity field changes caused by the mass changes of land and groundwater reserves(non-tectonic change factors),and effectively makes up for the deficiency of traditional well detection and other conventional means that can only roughly count the changes of shallow groundwater reserves.Based on the GRACE and GRACE-FO time-varying gravity field model CSR RL06 GSM data,this paper inverted the long-term changes in groundwater reserves in the North China Plain from 2002 to 2019,and quantitatively estimated the groundwater loss rate and its temporal and spatial evolution characteristics in North China during different periods of time.It provides an important quantitative reference basis for the rational development and utilization of regional groundwater and the rational formulation of water resources management plans.