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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Analysis of infrasonic and seismic events related to the 1998 Vulcanian eruption at Sakurajima
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Analysis of infrasonic and seismic events related to the 1998 Vulcanian eruption at Sakurajima

机译：分析与1998年樱岛火山爆发有关的次声和地震事件

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摘要

We present results from a detailed analysis of seismic and infrasonic data recorded over a four day period prior to the Vulcanian eruptive event at Sakurajima volcano on May 19,1998. Nearly one hundred seismic and infrasonic events were recorded on at least one of the nine seismic-infrasonic stations located within 3 km of the crater. Four unique seismic event types are recognized based on the spectral features of seismograms, including weak seismic tremor characterized by a 5-6 Hz peak mode that later shifted to 4-5 Hz. Long-period events are characterized by a short-duration, wide spectral band signal with an emergent, high-frequency onset followed by a wave coda lasting 15-20 sand a fundamental mode of 4.2-4.4 Hz. Values of Q for long-period events range between 10 and 22 suggesting that a gas-rich fluid was involved. Explosive events are the third seismic type, characterized by a narrow spectral band signal with an impulsive high-frequency onset followed by a 20-30 second wave coda and a peak mode of 4.0-4.4 Hz. Volcano-tectonic earthquakes are the fourth seismic type. Prior to May 19,1998, only the tremor and explosion seismic events are found to have an infrasonic component. Like seismic tremor, infrasonic tremor is typically observed as a weak background signal. Explosive infrasonic events were recorded 10-15 s after the explosive seismic events and with audible explosions prior to May 19. On May 19, high-frequency impulsive infrasonic events occurred sporadically and as swarms within hours of the eruption. These infrasonic events are observed to be coincident with swarms of long-period seismic events. Video coverage during the seismic-infrasonic experiment recorded intermittent releases of gases and ash during times when seismic and acoustic events were recorded. The sequence of seismic and infrasonic events is interpreted as representing a gas-rich fluid moving through a series of cracks and conduits beneath the active summit crater.
机译：我们目前提供的是对1998年5月19日在樱岛火山的火山爆发事件发生前四天记录的地震和次声数据进行详细分析的结果。在距离火山口3公里以内的9个地震次声台站中至少有一个记录了近百次地震和次声台事件。根据地震图的频谱特征，可以识别出四种独特的地震事件类型，包括以5-6 Hz峰值模式为特征的弱地震震颤，后来又转变为4-5 Hz。长期事件的特征是短时，宽频谱带信号，出现高频突发，然后是持续15-20秒的波尾波，其基本模式为4.2-4.4 Hz。长期事件的Q值范围在10到22之间，这表明其中包含了富含气体的流体。爆炸事件是第三种地震类型，其特征是窄带信号具有脉冲性高频起振，其后是20-30秒的波尾波，峰值模式为4.0-4.4 Hz。火山构造地震是第四类地震。在1998年5月19日之前，仅发现地震和爆炸地震事件具有次声成分。与地震震颤一样，次声震颤通常被观察为微弱的背景信号。在爆炸性地震事件发生后的10-15 s内记录了爆炸性次声事件，并在5月19日之前听到了爆炸声。5月19日，高频脉冲次声事件偶发发生，并在喷发后数小时内成群。观察到这些次声事件与大量的长期地震事件一致。地震-次声实验期间的视频报道记录了在记录地震和声学事件期间气体和灰烬的间歇释放。地震和次声事件的顺序被解释为表示一种富含气体的流体，该流体通过活动的山顶陨石坑下方的一系列裂缝和导管。

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