map of recent Gorda quakes. (click
for full size)
March 9: Earthquake activity has fallen off
substantially. In summary, given that this recent sequence
began with a large magnitude earthquake (5.2) and was
followed by a relatively low number of events per hour
that is consistent with aftershock activity, it seems
likely this was a tectonic sequence and did not have
a magmatic/hydrothermal component.
magnitude 5.2, 5.1 and 4.3 earthquakes occurred on the
Ridge segment over a 7.5 hr period beginning at
02:34Z on March 7. The SOSUS locations of these earthquakes
is 42-32.1'N 126-55.2'W which is along a section of
the Gorda Ridge that experienced a dike injection and
seafloor eruption in 1996. As of 1400Z, SOSUS has detected
228 earthquakes from this sequence with event counts
in the range of 13-27 per hour which significantly smaller
than the recent Endeavour swarm during its peak in activity.
Although earthquakes this large of magnitude on the
ridge-axis are uncommon, the extent of a possible magmatic
and hydrothermal component to this earthquake sequence
(if any) is unclear and seems unlikely.
Histogram of Gorda quakes. (click
for full size image)
Links to these events are available
at NEIC and UW seismic networks.
the Endeavour event (Feb-March 2005) at:
Endeavour Response Cruise