Shear-wave splitting beforeand after the 1999 Xiuyan earthquake in Liaoning, China

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 MS5.9 (ML5.3) 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.

Using seismic waveform data recorded at station Yingkou （YK） of Li-aoning Telemetry Digital Seismic Network, this paper studied the characteristics of shear-wave splitting before and after the Xiuyan Ms5.9 （ML5.3） earth-quake on November 29, 1999, with the SAM method （Gao et al）. The result shows that predominant polarization 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 regional tectonic stress field in North China. The time-delays increased before the Xiuyan earthquake, indicating stress accumulation before the mainshock. Predominant polarization of fast shear-waves at YK is also related to the spatial distribution of small earthquakes and correlated to the fault strike. The histogram of monthly average polarizations of fast shear-waves shows that the polarization of fast shear-waves seems to have changed from two months before the mainshock, but this needs to be verified with more data.