June 28, 2006:

SOSUS is currently detecting a relatively small, but ongoing earthquake sequence at the West Valley of the northern Juan de Fuca Ridge. The first earthquake, likely the mainshock, occurred at 23:21Z on June 27 2006 and was also recorded by the Pacific Northwest Seismic Network which assigned this event a magnitude of 4.4. Over the last 12 hours, 113 aftershocks have been detected occurring at a rate of 5-10 events per hour. The earthquakes from this sequence are centered (yellow dot) along the northeastern side of the valley, relatively distant from either ends of the ridge segment. This activity is significant in that the West Valley segment has not exhibited a large amount of seismicity during the past 15 years of SOSUS recording. We will continue to closely monitor this activity and will send another announcement if the activity increases significantly.

June 30, 2006:

The attached updated map shows locations of the m4.4 mainshock (yellow star) and the best located aftershocks (white circles). Activity has decreased in the last the last day to 1-2 events per hour.

WValleyEQsMap

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