Study of source mechanism of volcanic earthquake and volcanic tremor revealed by broadband seismic observations

宽带地震观测揭示的火山地震及火山颤震震源机制研究

• 批准号: 12640403
• 负责人: IDA Yoshiaki
• 金额: $ 2.3万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2000
• 资助国家: 日本
• 起止时间: 2000 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12640403/
• 关键词: Volcanic earthquake; Volcanic tremor; Asama volcano; Magma reservoir; Free oscillations of a fluid sphere; Eruption; Pressure source under a summit crater; 広帯域地震観測; A型地震; B型地震; N型地震; 火山性流体; 発生機構; 浅間山; 火山性地震・微動; マグマ; 火山ガス

ln Asama volcano, additional four seismic stations were recently installed near the summit crater in order to obtain the high quality records in closer distances to the hypocenter regions just below the crater. Using the new data, the hypocenters of the volcanic earthquakes were determined much more accurately, particularly in depth. High frequency earthquakes and low frequency events are concentrated into a shallow zone above the depths of 1 km underneath the crater. Some high frequency events are also observed below 3 km and there is a seismic gap between the two zones. The seismic gap agrees with the location of the pressure source which is estimated from the ground deformation. It is inferred that the gap zone corresponds to a magma reservoir and that shallower seismic events occur in and around the conduit to the summit crater. By GPS observation, the seismic swarm was associated with the crustal deformation and the pressure source of the deformation is the same region as the volcanic earthquakes just bellow the summit crater. The seismic swarm is considered to be caused by the pressure changes of the conduit.

LN Asama火山，最近在山顶火山口附近安装了另外四个地震站，以便获得距火山口下方的低核区域的高质量记录。使用新数据，更准确地确定了火山地震的低中心，尤其是深度。高频地震和低频事件集中在火山口下1公里深处的浅区域。在3 km以下还观察到一些高频事件，并且两个区域之间存在地震差距。地震间隙与压力源的位置一致，这是从地面变形中估计的。据推断，间隙区域对应于岩浆储层，并且较浅的地震事件发生在山顶火山口的导管内和周围。通过GPS的观察，地震群与地壳变形有关，变形的压力来源与火山地震的区域相同。地震群被认为是由导管的压力变化引起的。

项目成果

A. Sakuraba, J. Oikawa ald Y. Imanishi: "Free oscillations of a fluid sphere in an infinite elastic medium and long-period volcanic earthquakes"Earth Planets Space. 54. 91-106 (2002)

A. Sakuraba、J. Oikawa 和 Y. Imanishi：“无限弹性介质中流体球的自由振荡和长周期火山地震”地球行星空间。

Atsushi Sakuraba: "Free oscillations of a fluid sphere in an infinite elastic medium and long-period volcanic earthquakes"Earth Planets Space. 54. 91-106 (2002)

Atsushi Sakuraba：“无限弹性介质中流体球的自由振荡和长周期火山地震”地球行星空间。