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The Effect Of The Lithospheric Structure On Coseismic And Postseismic Deformation Of Intracontinental Large Earthquake

Posted on:2019-03-03Degree:MasterType:Thesis
Country:ChinaCandidate:H XuFull Text:PDF
GTID:2310330548451963Subject:Solid Earth Physics
Abstract/Summary:PDF Full Text Request
Before the triggering of a large earthquake,the region will undergo a period of tectonic loading which will cause the surface deformation.When the earthquake happens,it will lead a relatively clear coseismic rupture in a very short time.The aftershock sequence is always associated with postseismic deformation.Factors affecting postseismic deformation include not only the earthquake triggering faults and the magnitude of earthquake,but also the lithospheric structure.There exists great differences in both lateral and vertical lithospheric structure of the continent.The earthquake is one of the ways which shows the inner movement and the adjustment of energy.Different lithospheric structures have different influences on disparate seismic stages' deformation.It's researched that there exists great lateral differences in vertical lithospheric structure on both sides of Longmen Shan fault zone.The fact that the seismic sequence of Tangshan earthquake is clearly longer than that of Kunlunshan earthquake pushed us to study the influences on the coseismic and postseismic deformation which is caused by vertical differences in the lithospheric structure.With the help of the ABAQUS software and PSGRN/PSCMP program,We respectively build a two-diversion viscoelastic-plastic finite element model and a viscoelastic multilayered model to calculate the seismic deformation by changing the elastic modulus of the upper crust,the elastic thickness of the upper crust and the viscosity of the mid-bottom crust.Combing the calculated data,we can find something in common.The larger elastic modulus of the upper crust corresponds to larger coseismic deformation and shorter relaxation time.The thicker the elastic thickness of the upper crust corresponds to smaller relaxation deformation.The higher viscosity of the mid-bottom crust corresponds to the longer relaxation time and lower relaxation rate.The dip angle of fault mainly affects the type and value of coseismic deformation.The horizontal and vertical deformation of low angle fault are all higher than that of high angle fault.There exists a sunken area near the fault when the angle is bigger.The shovel type fault not only has a larger vertical coseismic deformation,but a sunken area near the fault which is similar with the high angle fault.Take the 1668 M8.5 Tancheng earthquake as an example,we get a coseismic rupture model based on the elastic dislocation theory with the constraint of surface rupture.In addition,we calculate the coseismic,postseismic deformation and Coulomb stress change of this earthquake with a viscoelastic multilayered model.The results show that the rupture fault of the earthquake is adextral strike-slip fault,which has slight thrust.The coseismic displacement of this event is very large.The accumulated energy is released thoroughly.The coseismic rupture of the 1668 Tancheng earthquake increased the Coulomb stress on the northwest,northeast and southeast faults of Tanlu fault zone.The Coulomb stress increases further due to the postseismic deformation.When the mantle is imposed different viscosities,the duration time which the deformation and Coulomb changes become stable will be different.However,the stable values of them are generally same.
Keywords/Search Tags:Seismic deformation, Finite element, Viscoelastic, The aftershock sequence, The coulomb stress
PDF Full Text Request
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