Abstract:
Based on the waveform data from
ML≥2.0 earthquakes during 2001—2010 in Anhui “Huoshan seismic window” recorded by Hefei, Lu’an and Baoziya stations of Anhui Digital Seismic Network, the amplitude attenuation coefficient
K and the predominant frequency attenuation coefficient
a were calculated, their temporal and spatial variations were analyzed, and the possible relationship of the variations with moderate-strong earthquake occurrence in eastern China and coda
Qc were discussed. The results indicate the following variation characteristics: ① In about six months before the
ML4.0 earthquake in “Huoshan seismic window”, the
MS5.7 Jiangxi Jiujiang earthquake and the
ML5.0 Henan Taikang earthquake,
K value and
a value decreased continuously to an abnormally low state; the average rates of decrease for
K and
a are 20%—35% and 45%—51%, respectively; the earthquakes occurred during the rising process of
K and
a values. ② By inspecting the plane view of
K variation, we found that earthquakes with abnormal
K value are mainly located at or near the fault intersections and distributed along fault zones. ③
K and
a values basically showed negative correlation with coda
Qc value, providing certain basis for further studying
Qc variation before and after moderate-strong earthquakes.