Study on attenuation characteristics of seismic waves from small-moderate earthquakes in “Huoshan seismic window”， Anhui Province

Based on the waveform data from M_L≥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 Q_c were discussed. The results indicate the following variation characteristics: ① In about six months before the M_L4.0 earthquake in “Huoshan seismic window”， the M_S5.7 Jiangxi Jiujiang earthquake and the M_L5.0 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 Q_c value， providing certain basis for further studying Q_c variation before and after moderate-strong earthquakes.