Research On Relationship Between Crustal Deformation Characteristics And Seismic Activity In Beijing And Its Adjacent Areas

A large number of studies indicate that crustal deformation is an effectivemethod to study tectonic movement, earthquake preparation and occurence. Beijingand its adjacent areas (metropolitan area) is the political, economic and cultural centerin our country.It is also an area with a frequent occurrence of earthquakes. Because ofits special seismic geological environment, it is of important theoretical and practicalsignificance to carry out the research on earthquake prevention and disaster reductionfor this area with the development of economic and society.In this paper, Beijing and adjacent areas was selected as the researching area.Take advantage of the crustal deformation observational data in this area, including allthe cross-fault deformation data. Combined with some fixed point deformation andGPS data in the Capital Region, we carried out the sthdy of fault activitycharacteristics, levels of activity, the intrinsic relationship between temporal andspatial evolution characteristics of modern crustal deformation and seismic activity,which provides a theoretical basis and background reference information for theCapital Region’s earthquake tracking and forecasting.The paper based on a comprehensive collection of data about tectonics, crustaldeformation, seismicity, geodesy, focal mechanism and other data, and studies a largenumber of research literature, I conducted systematic research and obtained thefollowing four main results:（1）First，I studied characteristics of fault activity in the Capital Region, bysubtracting monthly yearly technical ideas, completely and quantitatively calculate thecumulative slip of the fault, that horizontal and vertica1components of fault slip, andhorizontal tension or compression component, and calculate the fault slip rate by thecumulative method, studied the evolution characteristics of fault activity, and thenanalyzed their relationship with seismic activity. The results suggested that the levelof all faults activity is low in the Capital Region, currently, whether vertical activityrate of fault or the level activity rate is not large in the Capital Region, they are bothunder1.00mm/a; nature of the fault activities reflect that left-lateral activity of faultstrengthen, right-lateral activity weaken relatively, tensional activity strengthen,compressional activity weaken relatively; fault activity show a clear phasecharacteristic, the activity intensity and activity mode of a fault are different indifferent time; fault activity and earthquake activities have a certain relationship,regional fault activities strengthen before the earthquake, and fault activity has certainabnormal features before the strong earthquakes occure.（2）In order to quantitatively obtain evolution characteristic of the region’s faultactivity, based on rational calculation and objective analysis on basic parameters, thispaper analyzed deeply fault activity characteristic in view of temparial and spatial,combined with the actual earthquake cases occurring in the past, fault activity spatialand temporal evolution characteristic before and after strong earthquake wasdiscussed, anomalies of different stage and space in the course of spatial and temporal evolution of earthquake precursors were identified and extracted. The results showedthat before the occurrence of strong earthquakes, a clear mid-short-term anomaliesappears, in the view from time, earthquake generally occurred in the course ofanomalies accelerating, turning and restoring; From the point of space,2to3yearsbefore the earthquake, pressure or tensile of epicenter and its surrounding areachanged and gradually formed a pressure zone that contained epicenter area andpressure gradually decreased in the spatial distribution pattern in the area away fromthe epicenter. After the earthquake, the study area emerged a wide range of tensile in arelatively stable spatial distribution, which provide a reference for earthquakeprediction to determine the time and place.（3）In order to further study fault activity overall characteristics in the CapitalRegion, the principal component analysis and integrated parameter Rt of fault activitytwo kinds of new methods were used to obtain quantitatively the overall evolutionlevel of fault activity. Predecessors used the rate synthesis methods to deal with thisproblem, compared with the rate synthesis methods and its results, the methods usedin this paper are more objective, the results obtained can be more effective to obtainthe general characteristics of fault activity and beneficial to extract earthquakeprecursors information, which can be used as effective tools for earthquake predictionand precursory anomalies extracting.（4）Based on analying and researching on cross-fault data, in order to verify,complement and improve the results obtained above, this paper also studied part offixed deformation data (stretching strain) in capital area, calculated strain parameterssuch as maximum principal strain, shear strain etc. The results indicated that the strainparameters had a certain relationship with earthquakes, before and after strongearthquakes, plane strain state showed different evolution characteristics.Fault-crossing measurement in the Capital Region was conducted for decades,themassive observational data were accumulated, which laid a solid foundation forresearthing the regional crustal deformation, fault characteristic and levels of activityand the relationship with seismic activity. For the reasons above, this paper can studythe level of fault activity in the Capital Region, and analyze comprehensively andquantitatively cross-fault deformation data by new methods, effectively extractearthquake precursors information. The result that relationship between moderncrustal deformation characteristics of Beijing and adjacent areas and seismic activityobtained in this paper further enrich theoretical basis and background referenceinformationfor earthquake situation tracking and forecasting.