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CALIFORNIA STRONG MOTION INSTRUMENTATION PROGRAM
The California
Strong Motion Instrumentation
Program (CSMIP) was established in
1972 by California Legislation to
obtain vital earthquake data for the
engineering and scientific
communities through a statewide
network of strong motion
instruments. When the planned
network is completed, statewide
coverage will ensure that strong
ground motion for any moderate to
larger size earthquake in the state
will be recorded.
Network Installation and Maintenance
 CSMIP installs state-of-the-art
earthquake monitoring devices called
"accelerographs" at various
representative geologic foundation
materials throughout California to
measure the ground shaking. When
activated by earthquake shaking, the
devices produce a record from which
important characteristics of
ground motion (acceleration,
velocity, displacement, duration)
can be calculated.
In addition, earthquake monitoring
devices are installed in structures
such as buildings, hospitals,
bridges,
dams, utilities and industrial
facilities. Sites are selected by
engineers and scientists
representing industry,
government, and universities. The
program has installed more than 900
stations, including 650 ground-response stations, 170 buildings, 20
dams and 60 bridges.
Data Processing and Dissemination
Data from monitoring devices are
retrieved by modem and computers or
by physically recovering the records
at the station. Modern equipment is
designed to automatically call CSMIP
headquarters when it senses ground
shaking.
After an earthquake, records
collected by CSMIP are processed and
disseminated to engineers,
seismologists, building officials,
state and local governments and
emergency personnel throughout the
State. Since the program's
inception, records from numerous
earthquakes have been collected,
processed and distributed for
analysis. All processed data are
available upon request or can be
downloaded from the U.S. National
Center for Engineering Strong Motion
Data at
http://strongmotioncenter.org.
Data Interpretation
In 1989, CSMIP established a project
for data interpretation and
utilization. The primary objective
of this project is to increase the
understanding of earthquake ground
shaking and its effects on
structures through interpretation
and analysis studies of CSMIP data.
CSMIP holds annual seminars to
transfer recent research findings on
strong-motion data to practicing
seismic design professionals and
earth scientists. The purpose of the
annual seminar is to provide
information that will be useful
immediately in seismic design
practice and post-earthquake
response. The ultimate goal is to
accelerate the process by which
lessons learned from earthquake data
are incorporated into seismic code
provisions and seismic design
practices.
SAFER
STRUCTURES
As the network is expanded
statewide, new and important data
become available on the occasion of
each new earthquake. Significant
strong-motion records have been
obtained from destructive
earthquakes. Some examples include:
Instruments installed by SMIP
at different levels of the Imperial
County Services Building in El
Centro recorded the motion of this
modern multi-story building during
the 1979 Imperial Valley earthquake
and resulting damage to the
building. With these data, engineers
have assessed the causes of the
damage and reached a better
understanding of the performance of
this type of structure.
The ground motion records from the
1994 Northridge earthquake indicated
much higher shaking close to the
fault than was expected. The Uniform
Building Code has been revised and
requires designing buildings for
larger seismic force in the
near-fault zone.
Strong-motion records were also
obtained from several concrete and
steel buildings damaged by the
Northridge earthquake. These records
have helped engineers understand how
buildings respond to damaging
shaking and provided important
information about the integrity of
the building structure after the
earthquake.
CSMIP data from buildings have led
to improved formulas in the Uniform
Building Code for calculating the
building resonant vibration period,
a key parameter in
earthquake-resistant design.
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Strong-motion records were obtained
from the Imperial County Services
Building damaged by the 1979
Imperial Valley earthquake (first
from a damaged building). |
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CSMIP instruments are confirming the
effectiveness of a new concept in
earthquake protection design called
"base isolation." Base isolation is
designed to reduce the effects of
ground shaking, much like shock
absorbers in a car. A base-isolated
hospital building nearly 22 miles
from the Northridge earthquake
experienced much lower shaking than
nearby buildings without
base-isolation. CSMIP has recorded
the motion in base-isolated
buildings during several earthquakes
and the data are critical to
evaluating the new technology.
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Accelerometers were installed above
and below the isolators at the base
of the Los Angeles Fire Command
Center. |
As
these strong-motion records are
analyzed and interpreted by
engineers and seismologists, the
resulting knowledge provides the
basis for improvements in structural
design and construction. In
addition, the local building codes
and ordinances that specify
earthquake-resistant design and
construction practices will be
improved.
Earthquakes will continue to be a
fact of life in California. Their
effect on our lives and on future
generations will gradually diminish,
however, as we acquire and apply the
knowledge necessary to build safer
structures. |
Hospital
Instrumentation
The Office of Statewide Health and
Planning and Development (OSHPD)
arranged for CSMIP to begin
instrumenting hospital buildings in
1989. The program has instrumented
29 hospitals and health facilities
throughout California.
Bridge
Instrumentation
Since the 1989 Loma Prieta
earthquake, a comprehensive project
was initiated by the Department of
Transportation (Caltrans) and CSMIP
to instrument Caltrans bridges
throughout the state. This project
was in response to recommendations
by the Governor's Board of Inquiry
that Caltrans implement a
comprehensive seismic
instrumentation program to provide
measurements of ground shaking and
record the response of bridge
structures during earthquakes.
The project includes instrumentation
of highway bridges, free-field sites
near major bridges, and subsurface
geotechnical arrays. The program has
instrumented more than 60 Caltrans
bridges. In addition, all Caltrans
toll bridges will be extensively
instrumented.
The Golden Gate Bridge, Highway and
Transportation District arranged for
CSMIP to install 76 sensors at the
Golden Gate Bridge in 1995.
Additional sensors will be installed
after the retrofit of this landmark
structure is completed.
TriNet and
CISN
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In 1997, a
joint project, TriNet,
between the CSMIP, Caltech and USGS
at Pasadena was funded by the
Federal Emergency Management Agency
through the California Office of
Emergency Services. The goals of the
project are to record and rapidly
communicate ground shaking
information in southern California,
and to analyze the data for the
improvement of seismic codes and
standards.
In northern California, CSMIP is
partnering with UC Berkeley and USGS
at Menlo Park. In July 2001, the
California Office of Emergency
Services started to obtain funding
for the California Integrated
Seismic Network (CISN), a statewide
system that includes the TriNet
system. The CISN will improve
seismic instrumentation and provide
statewide ground shaking intensity
maps. It will also distribute and
archive strong-motion records of
engineering interest and
seismological data for all recorded
earthquakes, and provide training
for users. CISN
produces a ShakeMap of ground
shaking, based on shaking
recorded by stations in the
network, within minutes
following an earthquake. The
ShakeMap will identify areas of
the greatest potential damage
for use by the Office of
Emergency Services and other
emergency response personnel in
the event of a damaging
earthquake. ShakeMap can be
viewed at the CISN web site
http://www.cisn.org/shakemap.html. |
ShakeMap for the 1994 Northridge
Earthquake |
For More
Information
The California Strong Motion
Instrumentation Program is a program
within the California Geological
Survey of the California Department
of Conservation and is advised by
the Strong Motion Instrumentation
Advisory Committee, a committee of
the California Seismic Safety
Commission. Current program funding
is provided by an assessment on
construction costs for building
permits issued by cities and
counties in California, with
additional funding from the
California Department of
Transportation, the Office of
Statewide Health Planning and
Development, the California
Department of Water Resources, and
other agencies.
Requests for additional information
on the program should be directed
to:
California Department of
Conservation
California Geological Survey
Strong Motion Instrumentation
Program
801 K Street, MS 13-35
Sacramento, CA 95814
916-322-3105 916-323-7778 (fax)
Web site: http://www.conservation.ca.gov/cgs/smip
e-mail address:
smipdata@consrv.ca.gov |