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Address inquiries to:

Robert Dziak - Principal Investigator/Seismologist - robert.p.dziak@noaa.gov

 

Haru Matsumoto - Principal Investigator/Engineer (OSU) - haru.matsumoto@noaa.gov

 

Debbie Smith - Principal Investigator/Tectonics (WHOI) - dsmith@whoi.edu

 

Maya Tolstoy - Associate Investigator/Seismology (LDEO) - tolstoy@ldeo.columbia.edu

  Volcanic Seismicity - Mid-Atlantic Ridge at Lucky Strike, March 16-19, 2001  
 

 

 
 

Index map of Lucky Strike site, click for full size General location of the Lucky Strike site. See epicenter map for detailed view.

Event histogram chart, click for full size
Histogram showing the half-hourly number of seismic events during the swarm. Click for full-size image.

distance v. time plot

Plot of the along-strike distance versus time does not indicate the clear migration of epicenters associated with lateral dike injection, but shows that the entire segment responded to the magmatic activity.

Text of upcoming InterRIDGE Newsletter article

  
  epicenter map 09/24/01
Epicenter map of the 2001 Lucky Strike earthquake swarm. Click for full-size images.

At about 1530Z on JD 75 (Thursday, March 16, 2001), a seismic swarm with characteristics of magma dike emplacement was detected by an array of autonomous underwater hydrophones deployed by NSF and NOAA investigators in the North Atlantic. The activity is centered at 37 20'N, 32 15'W on the Lucky Strike Segment of the Mid Atlantic Ridge, which is also the site of the InterRIDGE sponsored MoMAR Project. Since the activity lies outside the array and generally in line with the array geometry, the locations show somewhat large errors, however in aggregate, they are clearly centered on Lucky Strike segment and appear to have originated near the volcanic edifice in the central rift valley.

  map of epicenters, click for full details
This diagram shows the change in rise times (time period from onset to peak for each earthquake) throughout the event. The cluster of short-rise-time events at the beginning of the sequence locates near the volcanic edifice at the Lucky Strike site

Field Observations:
Preliminary analysis of in situ observations of the Lucky Strike hydrothermal field obtained from submersible dives during July 2002 suggest an increase in diffuse venting, especially along the sides and base of the black smoker mounds, since the site was last visited in 1997 (Tim Shank, pers. com.). However, no evidence of recent lava flows has yet been observed, and all pre-existing hydrothermal vents appear to still be intact.

seismic spectrogram

The spectrogram of the initial 30 minutes of seismic activity shows the typical character of mid-ocean ridge magmatic seismicity: intense low-magnitude seismicity with accompanying continuous tremor and no large main shock