California Strong Motion Instrumentation Program

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. To date, the CSMIP has installed almost 1,400 stations that collectively account for more than 10,000 strong-motion sensors. These high-resolution instruments are installed at representative structures and geological settings: 937 ground-response stations, 273 buildings, and 115 stations at bridges, tunnels, and dams (CSMIP, September 2024).

The images below show typical installations of CSMIP instrumentation.

Accelerograph System Requirements

• Integrated Tri-Axial Accelerograph System Requirements (updated 2023)
• Central Recording Multichannel Accelerograph Recorder System Requirements (updated 2023)

We retrieve data from monitoring devices 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 can be downloaded from the Center for Engineering Strong Motion Data (CESMD). Reports are available through our Earthquake Data Reports page.

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. The proceedings from these seminars are available through our SMIP Seminar page.

Imperial County Services Building damaged by the 1979 Imperial Valley earthquake. This was the first time strong-motion records were obtained from a damaged building.

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

Accelerometers installed above and below the isolators at the base of the Los Angeles Fire Command Center.
• 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.

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; however, their effect on our lives and on future generations will gradually diminish as we acquire and apply the knowledge necessary to build safer structures.

Hospital Instrumentation

The California Department of Health Care Access and Information (HCAI) (formerly OSHPD) arranged for CSMIP to begin instrumenting hospital buildings in 1989. The program has instrumented scores of 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.

ShakeMap for the 1994 Northridge Earthquake

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 .

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