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  Seismic Activity - Endeavour Ridge- February-March, 2005  

(click image for full size)map of event location
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.

camera photo camera photo
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:
cruise summary map
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 ...


Map showing the location of the Endeavour earthquake swarm
Epicenter map
Epicenter plot by day
Red dots are epicenters of larger earthquakes located using 4 or more hydrophones. Black dots are smaller events that are located using 3 hydrophones and may not be as well constrained. Epicenters are plotted through March 1 (305 events).
Epicenters of earthquakes as a function of time. Black dots = 25 Feb; red dots = 27 Feb; Yellow dots = 28 Feb; White dots = 1 Mar; Pink dots = 2 Mar; Brown dots = 3 Mar.
Histogram of events plot
Time versus distance plot
Histogram of number of events vs. Time
(updated 3/24/05)
Time vs. Distance plot showing north to south distribution of earthquakes.
3D map view
3D map view
Oblique 3D view of the swarm area. Earthquake epicenters are white dots.
Oblique 3D view of the swarm area. Earthquake epicenters are white dots.

Last Updated: 03/25/05

Address inquiries to:
Oregon State University, Hatfield Marine Science Center, Cooperative Institute for Marine Resources Robert Dziak - Seismologist - robert.p.dziak@noaa.gov
Matt Fowler - Analyst - matt.fowler@noaa.gov


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