High precision relocations of deep (> 13 km) Hawaiian earthquakes:
Evidence for a mantle fault zone beneath Kilauea Volcano

by Cecily J. Wolfe
Hawaii Institute for Geophysics and Planetology
University of Hawaii at Manoa

3-4pm
Friday November 1, 2002
Refreshments served at 2:45pm
Munk Conference Room
Cecil and Ida M. Green Institute of Geophysics and Planetary Physics
Scripps Institution of Oceanography
University of California, San Diego
http://mahi.ucsd.edu/seminar/

Abstract

The abundant earthquakes in Hawaii provide key information on the nature
of magmatic and tectonic processes at this oceanic hotspot.  Here, we
present the results of an ongoing project to study earthquakes recorded on
the United States Geological Survey Hawaiian Volcano Observatory seismic
network.  We have applied waveform cross correlation analysis and high
precision relocation to 14,605 deep (> 13 km) earthquakes recorded from
1988-1998.  We find about half of the analyzed earthquakes are strongly
correlated multiplets that delineate fault zones in the lower crust
and mantle.  Relocations and focal mechanism analyses demonstrate that
mantle seismicity beneath Kilauea is focused on a primary fault zone at
30-km depth, with seaward slip on a low-angle plane, and other distinct
fault zones.  These results refute previous suggestions that hypocenters
at Kilauea outline a magma conduit through the lithosphere.  Rather,
we suggest deep seismicity at Kilauea reflects rupture in the brittle
lithosphere away from the zone of magma movement, although the earthquakes
are apparently induced by background stresses of magmatic origin.
In addition to the study of deep earthquakes, we will also present the
results of applying cross correlation analyses and relocations to 6,674
earthquakes located west of -155.5 degrees and recorded from 1988-1998.
This component of our study is aimed at understanding the characteristics
of faulting on the west flank of Mauna Loa.