A MATHEMATICAL SIMULATION FOR THE PATTERN OF SEISMIC TRANSFERENCE IN NORTH CHINA

Paper describes a certain process of solving a space-time inversion problem. A certain North China region is treated as a grillage of tectonic structures composed of 24 major faults and as an elastic-ideally plastic body in plane strain at a depth of 15 km. It is subjected to uniform stress along the boundaries. By means of the finite element method, the stress field is calculated and the zones of seismic risk are delineated in this region. By reducing the coefficient of friction in a fault from static to kinetic, stress and strain energy may be released there. Five major earthquakes in the last 12 years in this region are simulated in this manner. By comparing the stress fields before and after the stress release, one obtains the change in strain energy, fault offsets, areas of seismic risk etc. They are compared to data from actual measurements. If they don't agree well, tectonic framework, parameters of mechanical properties and external stress field are adjusted until they do.The results show that the present method can reproduce in essence the pattern of seismic transference in the last 12 years and may give some idea about the zones of seismic risk in the future. They also suggest that, after an earthquake, there are narrow sectors in the left-frontal part along the slippage directions that become safer than before, while in the remaining parts the danger of shear fracture increases.