New Instrumentation May Help Scientists Understand Earthquake Mechanics

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February 22, 2006

Hundreds of earthquakes occur every day around the world, most of them
underneath the oceans, while the vast majority of instruments used to
record earthquakes are on land.  As a result, advances in
understanding basic earthquake processes have been limited by the
available data. Scientists are improving this situation by developing
an instrument that records both small and large earthquakes on the
seafloor.

Jeff McGuire and John Collins at the Woods Hole Oceanographic
Institution (WHOI) plan to deploy 40 ocean bottom seismometers, or
OBSs, on the ocean floor along the East Pacific Rise in the Eastern
Pacific Ocean.  Their target area is a section of ocean about the
size of the states of Connecticut and Rhode Island combined.

The instruments will use a pair of seismometers, one known as a
broadband seismometer, the other as a strong-motion accelerometer, to
record the ground movements from undersea earthquakes, just like
seismic arrays on land.  They will be placed on the
Quebrada/Discovery/Gofar (QDG) transform fault system for one year
starting in early 2007.  This area is known to have large
earthquakes, greater than magnitude 5, preceded by foreshocks, or small
shocks around magnitude 3, in the last hour before a large rupture
occurs.  Current ocean bottom seismometers record moderate ground
motions from nearby small earthquakes and can register the foreshocks,
but do not have the range to record the main shocks, McGuire
said. 

McGuire and Collins have received a $1 million grant from The W. M.
Keck Foundation to develop a new suite of OBSs capable of accurately
recording both foreshocks and mainshocks.  Ten will be built, to
be used in conjunction with current instruments from the U.S. national
Ocean Bottom Seismograph Instrument Pool or OBSIP, which supplies OBSs
to researchers around the country for their research projects. 
WHOI and the Scripps Institution of Oceanography maintain and operate
the pool.

“This grant from the Keck Foundation has enabled us to take a major
step forward,” McGuire said.  “Together with existing pool
instruments and ship time, both supported by the National Science
Foundation, we will be able to record large undersea earthquakes
directly on top of the faults that generate them.  Although our
test area is in the middle of the Pacific Ocean, this technology will
have broad application to other faults zones, including those of
significant societal relevance such as the nearshore subduction zone
off Oregon and Washington.”

Advances in electronics in the past five years or so, including
electronics that require less battery power, have made a new generation
of OBSs possible.  While some parts of the new OBSs will be bought
from commercial firms, other aspects of the instruments will be
designed and built by WHOI scientists and engineers.  The new
generation OBS will be tested this summer and fall and prepared for
deployment on the East Pacific Rise in water depths of 3,500 to 4,000
meters (about 11,500 to 14,000 feet).
   
The W.M. Keck Foundation was established in 1954 in Los Angeles by
William Myron Keck, founder of The Superior Oil Company, with the goal
of providing far-reaching benefits for humanity.  With assets of
more than $1 billion, the Foundation is one of the largest
philanthropic organizations in the nation. Supporting pioneering
discoveries in science, engineering and medical research has been a
mandate of the Keck Foundation for a half-century. By funding the work
of leading researchers, the building of labs and research centers, and
the purchase of sophisticated instruments, the Foundation lays the
groundwork for breakthrough discoveries and new technologies that will
save lives, provide innovative solutions and add immeasurably to our
understanding of life on Earth and our place in the universe.

The Woods Hole Oceanographic Institution is a private, independent,
not-for-profit corporation dedicated to research and higher education
at the frontiers of ocean science. Located in the village of Woods Hole
in Falmouth, MA, its primary mission is to understand the oceans and
their interaction with the Earth as a whole, and to communicate a basic
understanding of the ocean’s role in the changing global environment.
Established in 1930 on a recommendation from the National Academy of
Sciences, the Institution is organized into five departments,
interdisciplinary institutes and a marine policy center, and conducts a
joint graduate education program with the Massachusetts Institute of
Technology.