Research on seismic stress triggering

This paper briefly reviews basic theory of seismic stress triggering. Recent development on seismic stress triggering has been reviewed in the views of seismic static and dynamic stress triggering, application of viscoelastic model in seismic stress triggering, the relation between earthquake triggering and volcanic eruption or explosion, other explanation of earthquake triggering, etc. And some suggestions for further study on seismic stress triggering in near future are given.

Seismic performances of dyke on liquefiable soils

Various field investigations of earthquake disaster cases have confirmed that earthquake-induced liquefaction is a main factor causing significant damage to dyke,research on seismic performances of dyke is thus of great importance.In this paper,seismic responses of dyke on liquefiable soils were investigated by means of dynamic centrifuge model tests and three-dimensional（3D） effective stress analysis method which is based on a multiple shear mechanism model and a liquefaction front.For the prototype scale centrifuge tests,sine wave input motions with peak accelerations 0.806 m/s2,1.790 m/s2 and 3.133 m/s2 of varied amplitudes were adopted to study the seismic performances of dyke on the saturated soil layer foundation with relative density of approximately 30%.Then,corresponding numerical simulations were conducted to investigate the distribution and variations of deformation,acceleration,excess pore-water pressure（EPWP）,and behaviors of shear dilatancy in the dyke and the liquefiable soil foundation.Moreover,detailed discussions and comparisons between numerical simulations and centrifuge tests were also presented.It is concluded that the computed results have a good agreement with the measured results by centrifuge tests.The physical and numerical models both indicate that the dyke hosted on liquefiable soils subjected to earthquake motions has exhibited larger settlement and lateral spread：the stronger the motion is,the larger the dyke deformation is.Compared to soils in the deep ground under the dyke and the free field,the EPWP ratio is much smaller in the shallow liquefiable soil beneath the dyke in spite of large deformation produced.For the same overburden depth soil from free site and the liquefiable foundation beneath dyke,the characteristics of effective stress path and stress-strain relations are different.All these results may be of theoretical and practical significance for seismic design of the dyke on liquefiable soils.

Equivalent formulae of stress Green's functions for a constant slip rate on a triangular fault

We present an equivalent form of the expres- sions first obtained by Tada （Geophys J Int 164：653-669, 2006. doi： 10.1111/j. 1365-246X.2006.03868.x）, which rep- resents the transient stress response of an infinite, homo- geneous and isotropic medium to a constant slip rate on a triangular fault that continues perpetually after the slip onset. Our results are simpler than Tada＇s, and the corre- sponding codes have a higher running speed.

F-structure model of overlying strata for dynamic disaster prevention in coal mine

The rupture and movement scope of overlying strata upon the longwall mining face increased sharply as the exploitation scale and degree growing recently,and the spatial structure formed by fractured strata became much more complex.The overlying strata above the working face and adjacent gobs would affect each other and move cooperatively because small pillar can hardly separate the connection of overlying strata between two workfaces,which leads to mining seismicity in the gob and induces rockburst disaster that named spatial structure instability rockburst in this paper.Based on the key stratum theory,the F-structure model was established to describe the overlying strata characteristic and rockburst mechanism of workface with one side of gob and the other side un-mined solid coal seam.The results show that F-structure in the gob will re-active and loss stability under the influence of neighboring mining,and fracture and shear slipping in the process of instability is the mechanism of the seismicity in the gob.The F-structure was divided into two categories that short-arm F and long-arm F structure based on the state of strata above the gob.We studied the underground pressure rules of different F-structure and instability mechanism,thus provide the guide for prevention and control of the F-structure spatial instability rockburst.The micro-seismic system is used for on-site monitoring and researching the distribution rules of seismic events,the results confrmed the existence and correct of F-spatial structure.At last specialized methods for prevention seismicity and rockburst induced by F-structure instability are proposed and applied in Huating Coal Mine.

Boundary integral equations for dynamic rupture propagation on vertical complex fault system in half-space:Theory

The boundary integral equation method （BIEM） is now widely used in numerical studies on earthquake rupture dynamics, and is proved to be a powerful tool to deal with problems on complex fault system. However, since this method heavily lies on the specific forms of Green＇s function and only the Green＇s function in full-space has a closed analytic expression, it is usually limited to a full-space medium. In this study, as a first step to extend this method to an arbitrary complex fault system in half-space, the boundary integral equations （BIEs） for dynamic strike-slip on vertical complex fault system in half-space are derived based on exact Green＇s function for isotropic and homogeneous half-space. Effect of the geometry of the complex fault system are dealt with carefully. Final BIEs is composed of two parts： contribution from full-space, which has been thoroughly investigated by Aochi and his co-workers by using the Green＇s function for full-space, and that from free surface, which is studied in detail in this study.

Experimental studies of focal mechanism based on the dynamic process of energy release

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