Research In Three-dimensional Crustal Deformation And Dynamic Mechanism On The Southeast Coast In Fujian

The Fujian region belongs to Wuyi-Dai Yunlong fold in South China fold system which is closelyrelated with circum-pacific seismic belt. It is one of the regions with active seismic activities in China.From the aspect of Plate Tectonics, Fujian province is located in the south-east of Eurasian plate margin,lies in the subduction from Pacific plate (Philippine plate) to the Eurasian plate and the inside of thecollision zone. Due to the joint impact of the movement of the Pacific plate (Philippine plate) and Eurasianplate, under the environment of long-term tectonic evolution, tectonic activities in Fujian Province ischanging constantly with extremely complex tectonic activities. Especially southeast coastal areas ofFujian which comes from the interaction between the Indian Plate and the Eurasian Plate, the PacificPlate as well as the Philippine Plate. There are extrusions from the Philippine Plate and the Pacific Platetowards the Eurasian plate, and pressure to the east deprived by Tibetan Plateau intensive uplift under thepressure of Indian plate as well as the expansion of Okinawa trench and other joint effects.The rapid development of geodesy allows the observations of high precision and high stability, accessto a large amount of information, and fast quasi-real-time information processing become possible, so as toprovide extremely important means for the quantitative study of geodynamics. It has an importantsignificance. In the three-dimensional deformation monitoring of crustal movement, Global PositioningSystem (GPS) of high-precision, Interferometry SAR (InSAR), Very Long Baseline Interferometry (VIBL),Artificial Satellite measurement technology (SLR) and other modern geodetic means are applied. Theobservation data of crustal Movement with intensive scope and time will become the basis of quantitativeresearch in the Earth Sciences.Using the geodetic means to obtain intensive three-dimensional crustal deformation field in to a widerange of time and space is extremely important for the study of the movement trends of crustal deformationand deep dynamic mechanism inferred. However, with further in-depth studies, the characteristics of thecrustal plate tectonics, fault activity characteristics, tectonic stress field, risk evaluation of seismogenicfault and other in-depth research of intensive mechanism become the focus. Therefore, combined withlarge-scale and intensive space-time three-dimensional crustal deformation field, use the geophysicalinversion, three-dimensional numerical simulation methods as well as other methods to research on theinternal dynamics mechanism triggering the crustal movements in multi-angle, multi-disciplinary andmulti-field is the main form of the current Geo-studies.In recent years, the law of motion on the southeast coast in Fujian and its neighboring regions,adjacent plate collision mechanism, rules of tectonic evolution, geodynamic processes, and influence ofenvironmental transitions has been a hot research topic in the field of Earth Sciences. Through the study ofthe motion characteristics of the southeast coastal areas in Fujian, it reveals the dynamic relationshipbetween the relative motion and deformation of the region with the active fault zone activities and provide important information for the earthquake prediction of southeast coastal areas in Fujian and study ofcontinental dynamics basis, which has a far-reaching significance for the establishment of numericalsimulation in this area and motion dynamics model, as well as providing an important basis for thecontinental dynamics research in this region. Discussion on these issues has important scientific andpractical significance for the development of the theory of Earth Sciences in the southeast coastal areas ofFujian, understanding the tectonic movement in southeast coastal areas of Fujian, demonstrating theinternal structure and mechanism of deformation of the southeast coastal areas in Fujian, analyzing andpredicting environmental change and disaster prevention as well as reduction.This paper focuses on the analysis of three-dimensional deformation field characteristics and itsdynamic mechanism of the southeast coastal areas in Fujian, based on the summary of the geologicalstructure of the southeast coastal areas in Fujian, fault activity characteristics, geological drilling survey,geophysical exploration data and other information, comprehensively use GPS, standards, InSAR and othergeodetic technical means to conduct careful research and comparison on activity trends, internaldeformation characteristics, stress-strain relations in the southeast coastal areas of Fujian block;comprehensively utilize geodetic inversion processing, three-dimensional numerical simulation and otherprocessing techniques for further analysis of its detail, deep features; and propose a reasonable mechanismof the deep structure of the southeast coastal areas in Fujian combined with the crustal movementcharacteristics of integrated regional peripheral South China plate and Taiwan region. In accordance withthe above purposes, main content and conclusions of this study include:1. A systematic collection of geological structure, physical exploration and crustal deformation data ofthe southeast coastal areas of Fujian, to master the geological unit evolution and tectonic settings, andconduct a preliminary study on the southeast coastal areas in Fujian regional tectonic and dynamicbackground. Geological data show that impact of large fracture system movement on which cannot beignored, the faults developed in the region is the important reasons for the uneven movement. Fujiansoutheast coastal structure pattern is mainly composed of north east towards fault zone (Changle-Zhaoanfault zone and coastal fault zone) and north west fault zone (Jiulong River fault zone, Jinjiang-Yongan faultzone, Xinghua Bay fault zone and Minjiang Fault zone), controlled by two groups and the quaternary faultzone; in the center of gravity datum (apart from the whole movement in the block), the crustal deformationmotion is small, and the results show that Fujian weak in the North and strong in the south, as well as weakin the west and strong in the south.2. Optimization and transformation of the existing crustal deformation monitoring network, designGPS and leveling scheme for layout of the urban agglomeration and national key project areas, so as toprovide evidence for the earth’s crust three dimensional deformation field and urban planning. This chaptermainly introduces the current level and GPS monitoring network results of Fujian southeast coastal areaand optimize as well as transform the current monitoring network, study and design the perfect monitoringscheme. Geodetic survey data show that the overall layout of existing surface movement depends on the surrounding large tectonic block relative motion state. From GPS data processing result, basic movementmoves along the SE direction, and has strong overall consistency while partition variation characteristics atthe same time. Differences movements are existed here.3. On the basis of traditional geodetic survey means, further study the InSAR and D-InSARtechnology for large scale, high precision vertical deformation of technical feasibility. The paper discussesthe application of SBAS-InSAR technology on the urban agglomeration land subsidence deformationmonitoring of Fujian southeast coastal area. D-InSAR methods of least east squares and multi-baselinewith small base set is applied, and use multiple platform to obtain image processing, combined withmultiple platform to obtain image processing, to describe the deposition velocity and characteristics ofFuzhou Basin, Quanzhou Basin and Zhangzhou Basin. Fuzhou basin acquired by InSAR technology is insedimentation condition, the Xiazhang region is in lifting state, while the Quanzhou area lifting is notobvious.4. Geodetic inversion problem is one of the core problems in in-depth survey of geodesy discipline,using the earth’s surface observed deformation material to speculate space change of the earth’s interiormedium physical state and evolution, it combines with seismology, earth physics and other subjects instudying earth dynamics and geophysical deep structure details the earth internal dynamic process andphysical property characteristics, its joint inversion is the most ideal tool for the geophysical data analysis.The thesis combines many kinds of data joint inversion fault parameters, applies dislocation model and theregional GPS and leveling as well as part of the InSAR results for fault of three dimensional slidingvelocity inversions through the particle swarm algorithm, and focused on analyzing fault characteristics ofChangle-Zhaoan fault zone. Joint inversion fault parameters obtained by using GPS, level, InSAR andother information are: fault movement rate is low, which changes only about1mm/a every year. Activitiesof Changle-Zhaoan fault zone are mainly compressional reverse rupture; forces of various parts of the faultzone are basically the same. The movement rate on the south of Changle-Zhaoan fault zone is high withstrong reverse fault activity; the middle part is weaker, and weakest in the north. The fault movement ofsouth section is larger than the north movement.5. The finite element method is widely used in earth science especially in geophysical and geodeticinversion field. The finite element method is a numerical calculation method based on variation calculusand split interpolation. It turns a problem of solving complex partial differential equation into thecalculating problem of Linear Equations. This paper used finite element method, and applies threedimensional numerical simulations to get stress strain field based on the viscoelastic constitutiverelationship for the numerical simulation of the stress strain field. Use three dimensional viscoelastic modelsimulation:1) the principal compressive stress is3-4times as principal tension, location of regional is NW(NWW)-SE (SEE). Under the action of this stress field, NE shows compressive movements towards faultzone, NW presents tension movement towards fault zone.2) Stress near (Changle-Zhaoan fault zone andcoastal fault zone) and North West fault zone (Jiu-long River fault zone, Jinjiang-Yongan fault zone, Xinghua Bay fault zone and Minjiang fault zone) are relatively concentrated and now active tectonicmovement affects the deformation characteristics of surrounding area.6. With the support of the acquisition of monitoring the earth measurement crustal movement, and onthe basis of understanding research regional geological tectonic characteristics, the paper analyzes thedeformation characteristics of combined with the above research results with inference of the cause of thecrustal deformation, and find out the force source of earth’s crust deformation, and studies the dynamicsmechanism of crustal deformation in Fujian southeast coastal area. Research on regional tectonic dynamicsmechanism: for Fujian southeast coastal and its adjacent area, the present crustal movement and thedeformation state is the result of many kinds of driving force: main force source of controlling southeastmodern crustal stress field and tectonic movement originate from the extrusion from Philippine plate andthe Pacific plate to the Eurasian plate, and the Pressure towards east derived from the Tibetan Plateauintensive uplift under Indian plate extrusion and Okinawa trench expansion as well as other joint action.