B-TYPE AND EXPLOSION EARTHQUAKES OBSERVED AT ASAMA VOLCANO, CENTRAL JAPAN

Authors
Citation
M. Sawada, B-TYPE AND EXPLOSION EARTHQUAKES OBSERVED AT ASAMA VOLCANO, CENTRAL JAPAN, Journal of volcanology and geothermal research, 63(3-4), 1994, pp. 111-128
Citations number
39
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Geology
ISSN journal
0377-0273
Volume
63
Issue
3-4
Year of publication
1994
Pages
111 - 128
Database
ISI
SICI code
0377-0273(1994)63:3-4<111:BAEEOA>2.0.ZU;2-V
Abstract
B-type and explosion earthquakes recorded at Asama Volcano, central Ja pan, are analyzed. Waveforms in B-type events are gradational from a h igh-frequency B-type (BH-type) to a low-frequency B-type (BL-type). Me dium-frequency B-type events also exist. The focal depths of BH-type e vents are deeper than those of BM-type and BL-type events. The low-fre quency contents (1-4 Hz) which predominate in explosion events and typ ical BL-type events are probably Rayleigh waves. The high-frequency co ntents (5-9 Hz) of BH-type events can be interpreted to be body waves. Medium-frequency B-type events exhibit the wave characteristics of bo th BH-type and BL-type events. We present a simple P-wave source model for B-type and explosion earthquakes. The P-wave source model can sat isfactorily explain the distribution of initial motions and difference in the wave characteristics of these events. The waveform difference between BH-type and BL-type events is attributable to the different so urce depths. We conclude that B-type and explosion events are due to g as explosion or gas emission.