Source mechanism of volcanic tremor revealed by waveform analyzes and fluid-dynamic experiments

1996年10月在阿萨马火山山顶火山口附近新建的4个台站的连续观测，获得了良好的火山地震和地震波形资料。将这些数据与山顶周围更远的较老台站的数据相结合，人们对火山地震和地震的性质有了更好的了解，总结如下：山顶火山口下方的火山地震(B型地震)和地震(低频或N型地震)的震中比以前认为的要浅得多，也更集中在一个狭窄的区域。西翼以下的其他地震(A型地震)往往与这些浅层地震分布在同一条线上，两组之间存在一定的地震空隙。火山口下浅层B类地震的S波震相在较老台站的波形中比较模糊，但在火山口附近的新台站获得的波形中识别得更清楚。震颤(低频或N型事件)的波形在*组处有一个陡峭的上升，可用来区分激励部分和共振部分。

Good waveform data of volcanic earthquakes and tremor have been obtained from continuous observations at four stations that were newly installed very close to the summit crater of Asama volcano in October, 1996. Adding the data to those from the older stations surrounding the summit in greater distances, the natures of volcanic earthquakes and tremor have been understood much better, as are summarized below.Hypocenters of the volcanic earthquakes (B-type earthquakes) and tremor (low frequency or N-type event) just bellow the summit crater have turned out to be much shallower and more concentrated into a narrow region than believed previously. Other earthquakes below the west flank (A-type earthauake) tend to be distributed on the same line as these shallow events with some seismic gap between the two groups.The S-wave phases of the shallow B-type events below the crater were quite ambiguous in the waveforms from the older stations, but they are identified more clearly in those obtained from the new stations near the crater. The waveform of the tremor (low frequency or N-type event) has a sharp rise at the ***set and it is usable to separate part of the excitiaion from the part of resonance.