New Views of Earthquake Swarms at Lo`ihi Submarine Volcano, Hawai`i Using Cross-Correlation and Double Difference Locations
Abstract
Volcanic activity at Lo`ihi submarine volcano is reflected in periodic earthquake swarms when hundreds to thousands of events occur over short time periods (days to weeks). Since 1990, Lo`ihi has experienced at least 11 earthquake swarms, recorded by the seismic network operated onland by the Hawaiian Volcano Observatory. Catalog locations for these events suggest that the swarms occur beneath virtually every part of the volcano. However, because Lo`ihi is located >30 km due south of Hawai`i island all of the permanent seismic stations lie in a limited azimuthal range and thus epicentral locations are poorly constrained. To improve our understanding of seismicity at Lo`ihi, we are re-examining its earthquake swarms using waveform cross-correlation and double-difference hypocenter relocation. Our analysis suggests that swarms occur in several discrete locations beneath Lo`ihi, and that the locus of swarm activity may migrate over longer (several year) time scales. In 1989 and 1990, swarms occurred to the NE of the volcano, near the SW edge of Kilauea volcano’s mobile south flank. In contrast, swarms in 1993, 1995 and the early days of the 1996 swarm took place to the west of Lo`ihi. The main phase of the 1996 swarm consisted of events occurring beneath the volcano’s summit, where activity has been largely concentrated since that time. Cross-correlation of Lo`ihi seismicity shows that some events are similar even between swarms; the early part of the 1996 swarm bears strong similarity to events that occurred in 1995. This similarity suggests that Lo`ihi’s swarms occur in weak zones that can be reactivated over long time scales. Events in the 1996 swarm are generally similar to one another, with a number of highly correlated clusters. These clusters occur throughout the swarm, with each cluster comprising events that span several weeks of activity. These events likely represent the slip of a plug above a magma reservoir, resulting in the formation of a pit crater at Lo`ihi’s summit. In all cases relocation of swarm activity collapses the epicenters into tighter clusters, although locations remain compromised by limited onshore station coverage.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.S21B2026H
- Keywords:
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- 7230 SEISMOLOGY / Seismicity and tectonics;
- 7280 SEISMOLOGY / Volcano seismology;
- 8419 VOLCANOLOGY / Volcano monitoring