Seismic Image of the Volcanic Tremor Source at Izu-Oshima Volcano, Japan
The 1986 fissure eruption of Izu-Oshima volcano was followed by a strong activity of volcanic tremor. To investigate the characteristics of the activity and its relation to the magma system beneath the volcano, two seismological surveys were carried out; one was an array observation of volcanic tremor and the other was an investigation of the crustal structure using seismic signals generated by an air-gun. The first study revealed that two separated sources radiated high frequency tremor and that they were located beneath the northwestern and the southeastern parts of the caldera floor. The analysis of the air-gun data by the method of the semblance depicted the three-dimensional image of a magma-filled crack elongating in the NW-SE direction beneath the caldera. From these results, we deduced a kind of fluid-driven crack model of volcanic tremor in which the outflow of magma through the crack tips generates high frequency tremor and resonates the magma-filled crack.
KeywordsCoherence Trench Geophysics Prep Fenton
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