Segmentations of active normal dip-slip faults around Ordos block according to their surface ruptures in historical strong earthquakes

From the results of researches of active faults in resent years, a correlation analysis between segments of the faults according to surface ruptures in nine historical strong earthquakes occurring in downfaulted system and active structures around Ordos block is conducted in paper. The result shows that there is a good correlation between them, except few individual data that have more uncertain parameters. It shows that intensity and segments of surface ruptures in these strong earthquakes are intrinsically related with the active structures. These strong earthquakes produced stable and unstable rupture boundaries of characteristic-earthquake type and successive occurrence of strong earthquakes on the different boundary faults in the same tectonic unit.

Stress and Strain Accumulation Due to a Long Dip-Slip Fault Movement in an Elastic-Layer over a Viscoelastic Half Space Model of the Lithosphere-Asthenosphere System

Most of the earthquake faults in North-East India, China, mid Atlantic-ridge, the Pacific seismic belt and Japan are found to be predominantly dip-slip in nature. In the present paper a dip-slip fault is taken situated in an elastic layer over a viscoelastic half space representing the lithosphere-asthenosphere system. A movement of the dip-slip nature across the fault occurs when the accumulated stress due to various tectonic reasons e.g. mantle convection etc., exceeds the local friction and cohesive forces across the fault. The movement is assumed to be slipping in nature, expressions for displacements, stresses and strains are obtained by solving associated boundary value problem with the help of integral transformation and Green’s function method and a suitable numerical methods is used for computation. A detailed study of these expressions may give some ideas about the nature of stress accumulation in the system, which in turn will be helpful in formulating an earthquake prediction programme.

Modifications in the Stress Field of a Long Inclined Fault Caused by the Welded-Contact Boundary Conditions across the Interface between Two Elastic Half-Spaces

In welded-contact boundary conditions, some stress components are not required to be continuous across the boundary between two elastic half-spaces. The purpose of this note is to study the modifications in the stress field of a long inclined strike-slip, dip-slip or tensile fault caused by the welded-contact boundary conditions across the interface between two elastic half-spaces. The Poisson’s ratios of the two half-spaces do not appear in the stress field of a strike-slip fault. In the case of a dip-slip fault, the Poisson’s ratio of the half-space in which the fault lies, has a significant influence on the stress field across the interface. However, for a tensile fault, the modification in the stress field is significantly affected by the Poisson’s ratios of both the half-spaces.

Displacement Field due to Nonuniform Slip along a Long Dip-Slip Fault in Two Welded Half-Spaces

The solution of static deformation of two homogeneous, isotropic, and perfectly elastic half-spaces in welded contact due to a long dip-slip fault with uniform slip is well known. The aim of the present article is to obtain the static deformation of two homogeneous, isotropic, and perfectly elastic half-spaces in welded contact due to nonuniform slip along a long dip-slip fault. The fault is vertical and lies entirely in the lower half-space, extending up to the interface. Four slip profiles are considered： lin- ear, parabolic, elliptic, and cubic. Closed-form expressions for the elastic residual field have been ob- tained for the different slip profiles. The displacement field due to four nonuniform slip profiles is com- pared with the displacement field due to uniform slip. For comparison, we have assumed the source potency for different slip profiles to be the same, which is achieved by taking the fault slip at the inter- face constant and varying the fault width. It is found that the displacement field varies significantly at the fault width rather than at the interface. Moreover, uniform slip along the fault makes the edges singular. This singularity at the lower edge is not present in the case of nonuniform slip along a long dip-slip fault.