2002年8月20日长白山天池火山小震震群研究

2002年7～9月，采用15台宽频带流动地震仪在长白山天池火山区进行了近3个月的地震观测，记录到大量发生在天池火山附近的地震和多次小震群。对2002年8月20日的小震群进行了分析，结果表明这些地震发生在长白山天池内的西南部，震源深度距离天池水面一般小于4km深，震群的震中位置呈北西向线性分布。地震记录的频谱分析表明，该震群为典型的火山构造类型地震。在观测中发现HSZ和DZD台的地震记录低频成份丰富，这可能与台站附近的局部介质变化或低速的断层带有关。我们认为震群可能是由火山深部活动诱发的局部断裂活动所引起。

A study on the micro-earthquake swarm occurred on Aug. 20, 2002 in Changbaishan Tianchi volcano

A 15 broadband portable seismograph network operating in Changbaishan Tianchi volcanic region during July and September in 2002 recorded a large number of earthquakes and several earthquake swarms occurred near the volcano. By analyzing the earthquake swarm recorded in 20 Aug., 2002, we found that the events are almost all located within the southwest of Tianchi Lake, and the focal depths are usually less than 4 km from the surface, the epicenters tend to northwest direction. The spectrum analysis shows that the earthquakes are typically volcanic tectonic earthquakes. We also found that the richness of low frequency components in the records of HSZ and DZD stations is related to the local variation of medium or low velocity fault zone near the seismic stations. We inferred that the earthquake swarm might be caused by the activity of small faults induced by deep volcanic active.