Present-day Crustal Movement Speed Field of China Continent Block Using Local Repeated GPS Network

Since 1992,China has established many large-scale high precision GPS crustal deformation monitoring network,including state high precision GPS Order-A network,China crustal deformation monitoring network,crustal deformation monitoring network in Qinghai-Tibet plateau,north China network,southeast coastal GPS network and Sinkiang network.GPS measurements of above GPS crustal monitoring networks are collected and they are reprocessed in ITRF97 frame.A complete GPS crustal movement image and speed field with uniform frame,the largest coverage and the most stations are obtained.Finally,a primary geo-scientific explanation of the speed field is given in the paper. China continent is located in the southeast of Eurasian plate.Its special tectonic location and lithographic structure after long-period complex evolvement makes the continental rock layer divided into several plates.And the main tectonic deformation happens at the faulted zone,folded belt and fault depression belt at the border of these plates,while the relative deformation inside the plates is small.There are mostly seismic active belts along the border of plates,thus the research of movement law and relative deformation is the hotspot that catches the attention of the geodetic world.According to the convergence velocity of plates,the uplifting extent of Pliocene epoch leveling and the gliding velocity of the fault,the compression velocity of each fault mountain system in the west of China continent can be estimated,and the movement velocity of each plate relative to Siberian land mass can be deduced.Moreover,the Euler poles and angular velocities of China continent blocks are figured by active fault gliding velocity according to plate geometry,and then average movement velocity vectors of each block are calculated,but they are all average value on the scale of geology.Movement images and relative movement images of each plate or block relative to one ITRF frame are obtained.However,China continent lacks a complete integer movement image of each main plate based on GPS monitoring.And surveying and data analyzing and processing of these GPS networks are accomplished by different units,thus the crustal movement images established by each GPS network are not the same due to different data processing method and datumFK(W39。40ZQin analyzing,which influences the proper utilization of GPS observation data and correct geoscientific explanation. This paper,collecting 6 items of materials of various high precision GPS crustal monitoring networks of China since 1992,uses uniform data processing method to reprocess data,carries out adjustment and deduces to the same coordinate frame datum,thus the complete GPS crustal movement image and speed field with uniform frame,the largest coverage and the most stations are obtained.This paper introduces the thought,method and final result of this work,and gives a primary geo-scientific explanation. The bearing and grade of the continent plates by GPS are in accordance with those by geological model,with difference in one or two,mainly the difference of nearly 900 in direction in Erdos plate.In the speed fields given by GPS,China continent land mass movement shows the difference in the west and the east,besides different movement velocity vector characteristics in each area.In the west the trend is moving towards the north and northeast,while in the east the trend is creep towards the south and southeast,with a huge north by north dextral shear zone. From GPS speed field,we can say the collision of Eurasian plate and Indian plate restrict the movement and deformation of China continent,especially in the middle west area.At the same time,the Pacific plate is diving towards the west,and the impact to China continent,especially northeast China land mass through Japanese Gulf can not be ignored.China continent is located in the intersection of Indian plate,Eurasian plate and Pacific plate,and the internal tectonic movement and deformation are the result of relative action.In the southwest side of China continent,Indian plate is advancing at the speed of 50mm/a; in the west of China, strong pushing force forms a series of adaxial arc reverse faulting zone; and in the east of China, the Pacific plate is diving tow ards Eurasian plate and the Japanese Sea is extending like an arc, equivalent to add a pushing force in the direction of southwest. Thus, the comprehensive effect of relative action betw een Indian plate, Eurasian plate and Pacific plate form the general strain field structure that the principal axis of stress is deflecting tow ards the east to northeast from near north and south in the west. Since the tertiary period, Indian plate is colliding with Eurasian further, and Qinghai-Tibet plateau is rising rapidly and extending around, causing strong pushing force in the south. And the south of tw o borders of north China sub-plate (w est border of Erdos plate)is under a force that decreases from the south to the north and pushes from near west and east to north by east. This pushing force will cause Erdos plate turn anticlockwise. China continent is a dynamic system consisting of many blocks and with complex geological structure, terrain and relief. With the further implement of China crustal netw ork project, more and denser GPS repeated surveying data are expected to be obtained, and more external crustal movement images can be given. Concerning geological and geophysical materials more, and using numerical mainfold method combining block discontinuous deformation analysis method w ith finite unit method, we can study the dynamic movement field and dynamics mechanism of China continent blocks better.