(click image for full size)
Updates:
March 9 Update: Five earthquakes occurred overnight on the ridge between the southern west valley and the northern Endeavour segment at ~48-18'N, 129-02W. Overall, however, earthquake remain at background levels.

Images from camera tow, read full report from Rapid Response Cruise.

Other news:
Three magnitude 5.2, 5.1 and 4.3 earthquakes occurred on the northern Gorda Ridge segment over a 7.5 hr period beginning at 02:34Z on March 7.

Other links covering this event:
Endeavour Event Links
(Associated Press, RIDGE 2000, etc.)

Note there was another swarm of earthquakes in this same area in October 2004.

Click on images below for full-size versions of the plots

Since Sunday morning 27 February at 0031Z, there has been an ongoing, intense earthquake swarm on the Endeavour segment of the northern Juan de Fuca Ridge. SOSUS has detected 3,742 earthquakes over a 5.5 day period. Event counts were as high as 50-70 per hour which is very similar in scale to past seafloor spreading events at Middle Valley in 2001 and Endeavour in 1999. We are currently working through the data, but have a preliminary location of 48-14.5'N 128-57.6'W which is ~36 km north-northeast of the Main Endeavour vent field and a few kms east of the intersection of the Heck Seamounts with the JdF Ridge axis. We have not located enough events yet to evaluate whether or not the earthquakes have migrated, or are currently migrating along the ridge axis. The sequence has also produced three large earthquakes (mb=4.5, 4.8, 4.9) which have been detected by NEIC, UW, PNSN. NEIC lists the location of the largest event a little east of the SOSUS location at 48-18.6'N 128-49.2'W. The Canadian Geological Survey/Pacific Geoscience Center has computed focal mechanisms for the largest earthquakes.

Follow the event response cruise on the R/V Thompson:

Response cruise summary map: white stars = CTD casts white lines & stars = CTD tows blue lines & dots = camera tow red dots = earthquake epicenters Bathymetry is NOAA multibeam.

Endeavour Response Cruise
March 9: It appears unlikely that this February/March 2005 earthquake swarm induced corresponding expression at the seafloor (e.g., eruptive flow) or in the water column (e.g., hydrothermal chronic or event plume). The in situ and ship-board physical and chemical data from the 3 long tow-yo casts and 7 vertical casts revealed no water column signal that can be clearly associated with the recent earthquake swarm, whether magmatic or tectonic.Full report ...

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