A newly‐developed numerical method, RFPA2D, used for analysis of rock failure process is applied to study the influence of mesoscopic heterogeneity on macroscopic behavior of rock failure and seismic sequence types. The failure processes of rock samples with 5 different kinds of heterogeneity are simulated, showing that rock failure with the different heterogeneity will produce different seismic sequence types, mainly including (1) main shockaftershock type, (2) foreshock‐main shock‐aftershock type, and (3) swarm type. Besides, the numerical simulation of rock failure with the different heterogeneity shows that the non‐linear behavior of rock deformation and fracture pattern as well as failure mode are obviously affected by the heterogeneity. With increasing the degree of rock homogeneity, the macroscopic failure process presents brittle behavior markedly. Meanwhile, it is also found that the failure modes of specimens are sensitive to the local variations of the mechanical properties of specimens with the same mechanical properties including the heterogeneity.
This paper made a numerical simulation to the basic tectonic stress field of Chinese mainland and its neighboring region using the visco-elasticity finite element model and the new published displacement rate result. Main contents include the simulation of maximum shear stress and its varying rate, the maximum shear strain and its varying rate, the shear strain energy density and its varying rate, In view of the high inhomogeneous distribution character of seismicity in space and time in Chinese mainland and its neighboring area, the normalized background energy value was given by means of normalized treatment to the earthquake energy release in the eastern and western parts of Chinese mainland. And the comparison of the simulation result with the actual seismicity was made. The ~esults show that the simulation values can explain well the earthquake distribution character of Chinese mainland and its neighboring area.
This paper presents the stress incremental rate of each element by using finite element numerical simulation way. Combined with the practical continent boundary condition and medium parameters, this paper applies the stress increment rate to the more practical modified cell automaton model according to the cell automaton principle. The paper preliminarily gives the more practical seismic space-time repeated evolutive maps, and compares the imitative seismic energy release with the real seismic energy release. It is thought that this model has its advantage over the old one whether in the seismic imitative characteristics or in the comparison with the real situation and is more practical model. Key words: finite element cell automaton model stress distribution seismic activity '
Using seismic waveform data recorded at station YK (Yingkou) of Liaoning Telemetry Digital Seismic Network, this paper studied the characteristics of shear-wave splitting before and after the Xiuyan M S 5.9 (M L 5.3) earthquake in November 29, 1999 with SAM method. The results show that the predominant polarizations of fast shear-waves at YK is in direction of ENE-WSW, consistent with the direction of regional principal compressive stress and also consistent with the direction of the regional tectonic stress field in North China; time-delays increasing before Xiuyan earthquake may shows accumulation of stress before earthquake. The predominant polarizations of fast shear-waves at YK are also related to the spatial distribution of small earthquakes and correlate with the fault strike. The histogram of monthly average polarizations of fast shear-waves shows that polarizations of fast shear-waves also seems to change from two months before the earthquake, but it still needs more data for verification.
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