MODELLING THE EVOLUTION OF A HALF GRABEN BASIN USING ELASTO-VISCOPLASTIC FINITE ELEMENT ANALYSIS
ZHANG Gui bin 1, Martin H.P. Bott 2(1 China University of Geosciences, Beijing 100083, China; 2 Department of Geological Sciences, University of Durham, DH1 3LE UK)
The evolution of a half graben basin bounded by normal faulting in the upper crust with a Byerlee type strength envelope has been modelled by elastoplastic finite element analysis. The substratum is assumed to be inviscid and the basin is filled by sediments lower in density than the crust. The nonlithostatic stresses, regions of failure and flexure profiles have been computed as the upper crustal layer is extended by progressive increments. The plastic deformation reduces the effective elastic thickness of the layer. The throw of the fault increases until thoroughgoing failure has become well established, after which the throw ceases to increase. Thus the strength of the layer limits the amount of subsidence and uplift that can occur. The thickness of the strong upper crustal layer and the density of the sedimentary infill are two important factors in controlling the width and maximum subsidence of the basins. Either increasing the layer thickness or increasing the density of the sedimentary infill has the effect on increasing the width and maximum subsidence of the basins. The most important application of the results is to interpret continental rift systems.
【Fund】： 高等学校博士学科点专项科研基金资助项目!(96 0 49111);; 英国皇家学会资助项目!(RoyalSociety— BritishPetroleumFellowshipAward)