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SAN FRANCISCO – The
California Geological Survey’s Strong
Motion Instrumentation Program, which
studies the effect of earthquake shaking
on structures and soil to help guide
engineering practices and protect public
safety, has been honored as one of the
top seismic programs of the 20th century
by the Applied Technology Council.
“This award comes
from an organization whose members use
the data we produce, so this is a
tremendous honor,” said State Geologist
Dr. John Parrish, head of the California
Geological Survey (CGS), part of the
state’s Department of Conservation.
“We’re very pleased
with and grateful for this recognition,”
said Dr. Anthony Shakal, the Supervising
Geologist in charge of the Strong Motion
Instrument Program (SMIP). “The fact
that the engineering community, which is
the target of our work, recognizes the
value of what we do tells us that we’re
successful.”
The Applied
Technology Council (ATC) is a nonprofit
corporation headquartered in Redwood
City. It was established in 1973 through
the efforts of the Structural Engineers
Association of California. ATC develops
and promotes state-of-the-art,
user-friendly engineering resources and
applications for use in mitigating the
effects of natural and other hazards on
construction. ATC also identifies and
encourages needed research and develops
consensus opinions on structural
engineering issues.
ATC’s board of
directors includes representatives
appointed by the American Society of
Civil Engineers, the National Council of
Structural Engineers Associations, the
Structural Engineers Association of
California, the Western Council of
Structural Engineers Associations, and
four at-large representatives concerned
with the practice of structural
engineering.
An ATC-commissioned
jury selected award recipients. SMIP and
the other winners will be honored at a
joint ATC-Engineering News Record event
April 17 – the eve of the centennial
anniversary of the Great San Francisco
Earthquake -- at the Westin St. Francs
Hotel in San Francisco.
SMIP was established
in 1971 after the devastating San
Fernando earthquake to obtain vital data
for the engineering and scientific
communities through a statewide network
of instruments. When activated by
earthquake shaking, these
“accelerographs” produce a record from
which the critical characteristics of
ground motion -- acceleration, velocity
and displacement -- can be calculated.
The information is
processed and disseminated to
seismologists, engineers, building
officials, local governments and
emergency response personnel throughout
the state. The data is used primarily to
recommend changes to building codes, and
assist local governments in their
general plan process. SMIP also partners
with the USGS, California Institute of
Technology and UC Berkeley in the
California Integrated Seismic Network.
Real-time data collected by the network
is used to produce a “ShakeMap” within
minutes of a strong earthquake to help
guide emergency response efforts.
SMIP has installed
and maintains recording instruments at
more than 1,000 locations statewide. The
devices are housed in a variety of
structures, including major bridges,
high-rise buildings, dams, hospitals and
industrial facilities. Among the
instrumented sites are the city halls of
Los Angeles, San Francisco and Oakland,
and the state capitol. Accelerographs
also are placed in open land to measure
the motion of the ground and the effects
of earthquake shaking on different types
of soils. An advisory committee of
engineers and scientists representing
industry, government and universities
help select SMIP’s station locations.
“I have a high regard
for the work that SMIP does,’ said
Christopher Rojahn, executive director
of the ATC and a former research
engineer involved in USGS’ strong motion
program. “The program is very well
organized. They’ve sought out the best
advice in designing their program and
provide a great service. The data SMIP
got from its instrumentation in
Parkfield is fundamentally important to
our understanding of ground shaking.”
More than two decades
of patience paid off for SMIP on
September 28, 2004 when a magnitude 6.0
earthquake struck in Parkfield, a hamlet
of 18 people located in rural southern
Monterey County about midway between
highways 5 and 101. The quake was
centered almost directly underneath an
array of 44 CGS and 10 USGS instruments.
As a result, an unprecedented amount of
information about how earthquakes work
has been collected.
SMIP began placing
instruments around Parkfield in 1982.
Why there? Parkfield had experienced
earthquakes in the magnitude 5.5-6 range
every couple of decades going back to
1857. The 2004 event was a late arrival:
the previous significant quake in the
self-proclaimed “Earthquake Capital of
the World” occurred in 1966.
Among the most
interesting findings out of Parkfield:
an oddity noted in the measured peak
acceleration, or movement. Shaking
occurred at about a third the force of
gravity in Parkfield, which is about six
miles northwest of the epicenter and
within a half-mile of the main branch of
the San Andreas fault. However, both
northwest and southeast of the village,
SMIP instruments measured shaking that
was three times as intense as the
shaking in Parkfield.
“We were stunned with
how much the ground shaking varied over
a relatively short distance,” Shakal
said.
That knowledge has
called into question whether one of
SMIP’s goals – at least one seismic
instrument in every California zip code
– is adequate. But as Shakal noted, the
data gathered at Parkfield showed the
benefits of sticking with a plan.
“Our greatest success
so far probably has been staying the
course,” Shakal said. “Thanks in no
small part to our advisory committee,
our stations have been well-placed and
we’ve done a good job of maintaining
them in the long haul. Those two things
go hand-in-hand. The excellent
performance we received from our
20-year-old instruments at Parkfield is
a tribute to our field technicians.”
Among SMIP’s current
projects are the instrumentation of the
new San Francisco Bay Bridge, several
hospitals around the state, and wharfs
at the Oakland, Long Beach and Los
Angeles harbors. SMIP is also updating
its older instruments, which capture
ground shaking on film that has to be
manually retrieved, with digital devices
that report in real time to a central
computer.
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