Seismic Activity at the Chanbaishan Tianchi Volcano in the Summer of 2002

Abstract

The level of seismicity in Chanbaishan Tianchi Volcano has increased obviously since 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 seismometers operating in the volcanic region in the 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. 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 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 the summer of 2002 might be caused by local faulting induced by deep volcanic activities.