云南地区S波非弹性衰减与ML震级测定研究

Study on Non-elasticity Attenuation of S Wave and Magnitude(M L)Determination in Yunnan Region

选取云南地震台网记录的地震波形资料,通过基于遗传算法的Atkinson方法分别计算云南3个区域的介质品质因子Q0值。根据云南地区地震波衰减的区域性差异,通过震级偏差统计分析了47个台站的单台ML震级偏差情况。结果显示:云南属于低Q0值地区,区域性差异明显。位于云南西部区域1的Q0值相对较高,为251.3;东部的区域3的Q0值次之,为216.9;中部的区域2的Q0值最低,为102.6。Q0值越小的地区,S波衰减程度越大,单台震级偏小于台网平均震级的台站也就越多。同一地区的台站在测定相同区域内的地震时,虽然地震波非弹性衰减程度相近,但由于受到各台站场地不同增益作用的影响,其单台震级偏差情况有所不同。

Using digital waveform data recorded by Yunnan seismic networks,quality factor Q 0 values of three regions in Yunnan are obtained by the iterative grid-search technique,as described by Atkinson.According of regional seismic wave attenuation characteristics in Yunnan,the single M L magnitude deviations of 47 stations are analyzed based on the magnitude deviation statistics.The results show that the overall Q0 values of Yunnan are relatively low and significantly different with different regions.The higher value of regional Q0 is 251.3 in region 1(located in the west of Yunnan),followed by a value of 216.9 in region 2(located in the east of Yunnan),a lowest value of 102.6 in region 3(located in the middle of Yunnan).The number of stations with single magnitude smaller than the average magnitude of the network is relatively large in the region with a lower Q0 and the greater attenuation of S wave.Although non-elasticity attenuation of seismic wave is similar,the single magnitude deviations are different due to the different site amplifications of each station,when earthquakes occurred in same regions are determined by stations located in the same region。