[SCG61-P23] Mechanics preserving co-seismic uplift and marine terraces:
dissymmetric patterns of co-seismic and inter-seismic deformation
Keywords:paleoseismic, mechanical model, Holocene marine terraces
As the calculation procedure, first, We give a constant displacement (10 m) to the edge of the oceanic plate and accumulate strain on the plate boundary. Next, We release all accumulated shear stress by coseismic fault slip,and obtain the vertical displacement pattern on the surface and the slip amount on the plate interface. Based on the fact that the principle of superposition is established in the linear elasticity theory, in this study, We separated the boundary conditions of both the interseismic period and the coseismic period,and calculated the respective vertical displacements and the residual amount by taking the sum. To verify the influence of irregularities on the actual plate boundary surface on the spatial pattern of vertical displacement, We also calculated two patterns for the case where irregularities were locally placed on the plate interface.
As a result of the calculation, we found that the interseismic slip amount in the no-cuppled area converged to 0 in the vicinity of the coupled area, and the coseismic slip amount was not uniform, and occurred across the plate boundary surface. This suggests that the slip on the plate boundary is intermittent in the seismic cycle. Next, from the vertical displacement residuals, we found that their spatial patterns at the interseismic period and the coseismic period were different.Furthermore, when local irregularities are placed on the plate boundary surface, it was found that the spatial pattern of the coseismic uplift is different corresponding to the slip amount of each model. This suggests that the height records the slip amount, and the shape of the plate boundary surface attributes actual coastal terrace formation. The consequence of this study is that the slip on the plate boundary is intermittent, and the coastal terraces depend on the coseismic slip.Therefore, the model in this study will give meaning to estimate the paleoseismic image from the height of coastal terraces.