Explosion earthquake

Japanese: 爆発地震 - ばくはつじしん（英語表記）explosion earthquake

Andesitic volcanoes exhibit explosive eruptions, and the earthquakes that accompany these eruptions are called explosion earthquakes. Generally, they are rarely felt by the human body; what is felt by the human body is usually the blast pressure that accompanies the explosion. When explosion earthquakes are observed using numerous seismometers placed on the mountain, it is found that the initial movement of seismic waves is a "push" in all directions from the crater, which is interpreted as being due to a sudden expansion occurring within the volcanic conduit. When the epicenters of explosion earthquakes are located, they are found to be distributed up to about 1 km from directly below the crater.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

安山岩質火山は，爆発的噴火を示すが，この噴火に伴って生ずる地震を爆発地震という。一般に人体に感ずることはまれであり，人体で感ずるのは爆発に伴って生ずる爆圧であることが多い。爆発地震を山体に置いた多数の地震計で観測すると，地震波の初動が火口からすべての方向に〈押し〉であることがわかり，これは火道の中で急激な膨張が発生したためと解釈される。爆発地震の震源を求めると，火口直下から1kmくらいにまで分布している。

出典　株式会社平凡社世界大百科事典第２版について　情報

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