Magma Chamber Recharging During Eruption and Tectonic Influence on Reservoirs: an Example From the 1986 Eruption of Izu-Oshima
Abstract
The eruption of Izu-Oshima in 1986 consisted of two phases and, for an event in that tie period, was well monitored by leveling surveys, tiltmeters and borehole strainmeters. Strain and tilt data for the first stage of the eruption are very coherent, show no obvious indications of precursory change and require a sub-vertical prolate spheroid source at about 4 km depth. Comparison of the continuous deformation data with well observed estimates of erupted volume (made frequently over the several days of the phase 1 activity) require replenishment of the shallow reservoir from a deeper (~30km) source during and following the eruptive activity. The second stage was preceded by clear strain and tilt changes indicative of dike formation and both data types show that significant deformation continued for days following the cessation of eruptive product; in fact the majority of magma movement was from a reservoir into a large dike (extending north-west south-east) that did not break the surface; the top depth is constrained primarily by elevation changes determined by line level surveys before and following the eruption. The strain data require a large dike contribution together with a deflating reservoir at about 10 km depth. We get an improved fit if the reservoir is a vertical oblate spheroid aligned with the dike direction i.e. flattened normal to the maximum tension direction in the crust that results from plate bending as it subducts.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.V44C..03L
- Keywords:
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- 8419 VOLCANOLOGY Volcano monitoring;
- 8488 VOLCANOLOGY Volcanic hazards and risks;
- 8494 VOLCANOLOGY Instruments and techniques