Background Information

Perhaps the most impressive demonstration of the utility of the SOSUS hydrophone network for the monitoring of oceanic seismicity occurred in June and July of 1993. A swarm of small events was detected in real time, and was determined to be occurring on the Juan de Fuca Ridge crest just north of Axial Seamount. The source area moved about 40 km along the ridge crest in the span of a few days, suggesting a magma intrusion. The extra activity can be seen in the earthquake map for the second quarter of 1993, at 130° W, 46.5° N. Fortuitously, the swarm occurred in summer, and research ships were scheduled to work in the vicinity. The Canadian ship Tully, and the NOAA ship Discoverer were rerouted to investigate the site. Plumes of heated water and subsequently fresh lava, were discovered at the site.


The Animations

Animations of the earthquake swarm show the movement of the source locations along the segment. Note that you will need an MPEG viewer for your Web client, and that the files are about 1800k and 700k in size respectively.

blue ball icon Swarm at 1-hour intervals

blue ball icon Swarm at 3-hour intervals

blue ball icon Swarm at 4-hour intervals in 3D view

Address inquiries to:

Chris Fox - Principal Investigator (
Tony Schreiner - Analysis, and Modeling
Bob Dziak - Analysis and Event Detection (
Andy Lau - Data Processing Methods (
Haru Matsumoto - Engineering (

RETURN icon Return to COAXIAL home page.