Bulletin of the Seismological Society of America; April 2001; v. 91; no. 2;
p. 178-190; DOI: 10.1785/0119990170
© 2001 Seismological Society of America
Seismicity and Velocity Structure of Loihi Seamount from the 1996 Earthquake Swarm
J. Caplan-Auerbach and
F. K. Duennebier
Department of Geology and Geophysics
University of Hawaii
Honolulu,
Hawaii
The largest earthquake swarm yet recorded on Loihi submarine volcano took
place in July and August of 1996. The swarm consisted of two phases of seismic
activity and was associated with the formation of a pit crater and additional
faulting of Loihi's summit platform. The first phase of activity was comprised
of predominantly high-frequency events scattered over the southern flanks of
the volcano. Following a day of seismic quiescence, the second phase of
activity began, consisting of lower-frequency earthquakes with strong
T-phases. The phase 2 events took place beneath Loihi's summit,
presumably marking the formation of the pit crater, Pele's Pit. Data obtained
by an ocean-bottom seismometer (OBS) on Loihi during the swarm help constrain
a new velocity model for Loihi. The relocated earthquakes, combined with other
characteristics of the swarm, enabled us to develop a model for the events
leading up to the formation of Pele's Pit that includes (1) a prolonged
eruption, (2) a tectonic event beneath Loihi's south flank, and (3) the
drainage of a shallow magma chamber.
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