Characteristics of the correlation coefficient of spectral amplitude of earthquake sequences in western Yunnan region since 2008

Using digital seismic waves recorded by Yunnan Digital Seismic Network, we calculated the correlation coefficient of spectral amplitude of six M_S≥4.0 earthquake sequences occurred from 2008 to 2011 in western Yunnan region. The results suggest that the correlation coefficient of spectral amplitude of earthquake sequences are generally high value, no matter the sequence is foreshock, main shock-aftershock or earthquake swarm, which may be caused by high stress filed in the source region. A smaller correlation coefficient of spectral amplitude, which means less consistency of focal mechanisms and low level of stress filed, can be used as an index to predict that larger earthquakes will not follow behind. The correlation coefficient of spectral amplitude of foreshock sequence is larger; however, a larger correlation coefficient does not indicate the earthquake sequence is foreshock. A larger correlation coefficient of spectral amplitude only implies high level of the stress field, but it is beneficial to occurring M_S≥5.0 earthquake in the source region.