Hydroacoustic Detection of Recent Seafloor Volcanic Activity in the Southern Indian Ocean
Abstract
We report preliminary results of a joint hydrophone experiment between researchers at NOAA/Oregon State University and CNRS/University of Brest. The objective of the project is to record the low-level seismic activity (magnitude > 2) associated with the Indian Ocean ridge system and surrounding inter/intra-plate areas using a network of temporary (autonomous) hydrophones combined with the 2 permanent hydro-acoustic stations of the Comprehensive nuclear-Test-Ban Treaty Organization (CTBTO) deployed in the SOFAR channel of the Indian Ocean (Diego Garcia Island and Cape Leeuwin). The temporary array was deployed in late Spring 2006 and recovered in early 2008 using the French R/V Marion Dufresne. Both the temporary and permanent hydrophone systems take advantage of the efficient propagation of sound in the oceans to map the locations of low magnitude seafloor earthquakes throughout the Indian Ocean Basin. To date, over 2,000 earthquakes have been located along the Southwest, Central, and Southeast Indian Ridges. Moreover, an impressive sequence of volcanogenic signals has also been identified. The first was a 6-week long series of broadband (1-125 Hz) explosion signals originating from an area roughly 500 km southeast of the Amsterdam Island. The broadband signals from this seafloor volcano frequently developed into harmonic tremor, with a fundamental of 15 Hz and up to 10 overtones visible in the spectra. The tremor also exhibited changes in harmonic frequency while maintaining its spectral spacing (gliding). The transitory character of the volcanic signals (explosions versus harmonics) implies a source vent with a Strombolian eruption style that may form a temporary lava "cap" allowing for brief periods of resonance before the cap is breached by explosive activity. We have also identified, 1) a prolonged earthquake sequence of short-duration, impulsive events located along a segment of the SEIR, and 2) several high-frequency harmonic arrivals similar to iceberg "tremor" observed in other southern ocean acoustic datasets. Preliminary analysis suggests these two sets of arrivals are likely volcanogenic and cryogenic respectively, however incorporation of the CTBTO data is yet required to refine our source locations.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.T51B1888D
- Keywords:
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- 7280 Volcano seismology (8419);
- 8178 Tectonics and magmatism;
- 8416 Mid-oceanic ridge processes (1032;
- 3614);
- 8428 Explosive volcanism