2002年夏季长白山天池火山区的地震活动研究

Seismic activity at the Changbaishan Tianchi volcano in the summer of 2002

20 0 2年6月以来,长白山天池火山区的地震活动明显增加.本文利用2 0 0 2年夏季布设在长白山天池火山区15套宽频带流动地震台站的记录资料,对天池火山区的地震活动进行了研究.地震观测结果表明,2 0 0 2年夏季长白山天池火山日平均地震发生频次超过30次.地震主要位于长白山天池西南部和东北部两个区域,震源深度较浅,离地表的深度一般小于5km .天池西南部和东北部的地震,b值存在较大的差异.火山区地震记录的频谱分析和时频分析结果表明,这些地震主要为火山构造型地震.HSZ和DZD等台站地震记录中丰富的低频成分,可能与台站附近的局部介质或断层带有关.我们认为2 0 0 2年夏季频繁发生的地震和小震震群活动是由火山深部活动诱发的局部断裂活动引起.

The level of seismicity in the Changbaishan Tianchi volcano has been increased obviously since the June of 2002 In this paper, the seismic activity of the Changbaishan Tianchi volcano is studied by using the data recorded at 15 broad-band portable seismographs operating in the volcanic region in summer of 2002 The result shows that the average rate of seismicity is more than 30 events per day in this area during summer of 2002 Most earthquakes occurred in two areas, southwest and northeast of the Tianchi caldera. The focal depths are shallow, and usually less than 5km from surface. The b values of events occurred in southwest and northeast areas are quite different from each other. Seismic spectral and time spectral analyses show that the events occurred in the summer of 2002 are all of volcano-tectonic earthquakes. The obvious 2Hz low frequency component in seismic records at stations HSZ and DZD is mainly caused by local variations of media and low velocity fault zones near the two stations. We infer that the large number of earthquakes and earthquake swarms occurred in summer of 2002 might be caused by local faulting induced by deep volcanic activities.