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.

The strong motion instrumentation network collects new and valuable data about seismic activity and structural performance with each earthquake. Some key examples include:

• Performance of multi-story buildings: Instruments installed by CSMIP at different levels of the Imperial County Services Building in El Centro recorded the motion of this multi-story building during the 1979 Imperial Valley earthquake. The recorded data helped engineers analyze the causes of structural damage and better understand the performance of this type of structure during seismic shaking.
• Ground response in near field: Ground motion records from the 1994 Northridge earthquake revealed unexpectedly high levels of shaking near the causative fault. This discovery led to revisions in the building code that require designs to account for greater seismic forces in zones near active faults.
• Performance of concrete and steel buildings: Strong-motion records collected from the 1994 Northridge earthquake at several damaged concrete and steel buildings improved engineers’ understanding of structural responses to intense shaking and provided valuable information for assessing post-earthquake building integrity.
• Building resonant vibration period: Data from CSMIP instrumented buildings have improved formulas used in the building code for calculating the resonant vibration period for different buildings, which is a key parameter in earthquake-resistant design.



• Base isolation effectiveness: CSMIP instruments have validated the effectiveness of base isolation technology, which works like car shock absorbers to reduce the impact of ground shaking. For example, a base-isolated hospital located nearly 22 miles from the Northridge earthquake epicenter experienced significantly lower shaking compared to nearby non-isolated buildings. Data from multiple base-isolated buildings have been critical for evaluating this technology.

  The analysis and interpretation of strong-motion data by engineers and seismologists continues to drive improvements in structural design, construction practices, and local building codes, ultimately enhancing earthquake resilience. While earthquakes remain a reality in California, advancements in engineering and construction will help mitigate their impact on the built environment.

Hospital Instrumentation

Since 1989 CSMIP has collaborated with the California Department of Health Care Access and Information (HCAI, formerly OSHPD) to instrument over 80 hospitals and health care facilities across the state. These efforts aim to enhance seismic safety in healthcare settings.

For a detailed overview, including a list of instrumented hospital buildings and the benefit of seismic instrumentation, refer to the instrumentation White Paper prepared by the Hospital Building Safety Board’s Instrumentation Committee. The document is available for download on the HCAI website:

https://hcai.ca.gov/wp-content/uploads/2023/11/Instrumentation-White-Paper-FINAL-10.26.23-A.pdf

Bridge Instrumentation

Following the 1989 Loma Prieta earthquake, the California Department of Transportation (Caltrans) and CSMIP launched a comprehensive seismic instrumentation project in response to the Governor's Board of Inquiry recommendations. The project focuses on recording ground shaking and the structural responses of bridges 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 80 Caltrans bridges including the major toll bridges and has installed over 30 geotechnical arrays.

In 1995, the Golden Gate Bridge Highway and Transportation District arranged for CSMIP to install 76 seismic sensors at the Golden Gate Bridge. Additional sensors were installed after the retrofit of this landmark structure was completed. As of today, the Golden Gate Bridge boasts a total of 122 sensors at the site, including two geotechnical arrays near the ends of the bridge.

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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