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Seismic pulses suggesting an implosive source at the 1989 Ito‐Oki Submarine Eruption, central Japan
Author(s) -
Ukawa Motoo,
Obara Kazushige,
Fukuyama Eiichi
Publication year - 1991
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/91gl01068
Subject(s) - geology , seismology , seismogram , crust , shear (geology) , azimuth , impact crater , submarine , geophysics , petrology , physics , oceanography , astronomy
Four unusual seismic pulses of magnitude about 2 were observed at the 1989 Ito‐oki submarine eruption on July 13, 1989. Their seismograms show two distinct characteristics; ineffective shear wave excitation and downward motions of P onsets for all azimuths. Source mechanisms are studied by using data obtained on the local seismic network. Hypocenters were estimated to be in a very shallow part of the upper crust beneath a new crater found after the eruption. The downward first motion and ineffective shear wave excitation are difficult to explain simultaneously by a double couple type source mechanism, suggesting an implosive type source.