Numerical Simulation Of Crustal Block's Deformation Coupled With Earthquake Events Of Spring-Block Model

Earthquakes in the continental lithosphere are the result of tectonic motion. Seismicity is related to stability of fault rather than its strength. Rupture of fault which occurs on the boundary of a crustal block is a consequence of motion and deformation of tectonic plates. For studying mechanism of rupture of fault, deformation of interior plate by tectonic motion should be considered. In this paper, energy statistics is used to analyze the spatial and temporal distribution of earthquakes around the world, China continental seismic regions and tectonic twist nodes. Distribution of seismic regions is simulated by a viscoelastic two-layer model. Transfer of stress and dynamic interaction in the viscoelastic crust are studied by numerical simulation under various kinds of boundary conditons. A numerical method of the finite element coupled with spring-block model is developed to simulate the system of faults and crustal blocks. Heterogeneous slip of a fault can be studied with distributed velocity un the spring-block model. The coupled model is applied to analyze the dynamics of movement of the Chuandian block and seismicity on boundary faults. The coupled model provides a way to link slow motion of a large-scale continental plate with sudden small-scale rupture of faults. It can be used for theoretical and practice application.The active and inactive periods of the world seismic zones are discussed further. The temporal change of great earthquakes in the circum-Pacific belt and Mediterranean-Himalayan belt is examined. There are eight periods which are more than that proposed by Mogi in last century. These periods are 1897-1916, 1917-1933, 1934-1951, 1952-1970, 1952-1971, 1972-1979, 1980-1998 and 1999-2002. In the Mediterranean-Himalayan seismic zone, the activity of great earthquakes is remarkably high during periods 1897-1917, 1934-1951, 1972-1979 and 1999-2002, appreciably low in the periods 1917-1933, 1952-1971 and1980-1998. The northern Pacific seismic belt is active in the inactive periods of Mediterranean-Himalayan seismic zone. The activities of southwest and southeast Pacific belts do not show such a regular pattern. So during different periods, there are two types of seismic distribution around the world. One is the circum-Pacific belt, and another is the latitudinal belt which joining the Mediterranean-Himalayan seismic zone with southwest and southeast Pacific belts. These results suggest that large earthquakes are strongly coupled on a global scale.There are four tectonic twist nodes, i.e. Asam, Pamir, Hunchun and Taiwan, around China continent. The seimic activity in these areas can be devided into micro-dynamic periods. The Hunchun deep earthquake zone and Taiwan are located in the west-Pacific tectonic belt of the eastern Eurasia plate. So they have similar temporal seismic characteristics. The periods of accumulation and release of stress in Pamir are shorter than those in Asam. The activity of tectonic twist nodes sometimes is related with space-time distribution of intracontinent earthquakes.For understanding the transfer of stress of the brittle-ductile model, a simplified model of two-layer viscoelastic lithosphere is built. Shear stress is applied on its boundary. The result comparison with Kusznir's model demonstrates that theIndia-Eurasia collision affects the wild deformation of China continental seismic zones. The heterogeneous brittle-ductile models with constant stress and constant velocity boundary conditions show that stress transfers from the ductile layer to the brittle layer, and the heterogeneous ductile layer also affects stress distribution of the brittle layer. The stress would be heterogeneous in the brittle layer along horizontal direction because strain difference of layer's interface controls transfer process of stress. As a conclusion, the brittle-ductile coupling produces the quick transfer of stress, and the deep heterogeneous ductile layer generates stress distribution and dynamic process in the brittle layer.Stress process and redistribution of a strike-slip...