California Earthquake Early Warning Program
Earthquake Warning California
On the 30th anniversary of the deadly Loma Prieta earthquake, the Governor, the Director of the California Governor’s Office of Emergency Services (Cal OES), UC Berkeley, United States Geological Survey (USGS), Senator Jerry Hill and others announced the launch of the nation’s first statewide Earthquake Early Warning System, Earthquake Warning California.
The California Earthquake Early Warning System marries a new smartphone application called MyShake with warnings issued through operating systems and Wireless Emergency Alerts (WEA). The system uses ground motion sensors from across the state to detect earthquakes before humans can feel them and will notify Californians so that they can “Drop, cover and hold on” in advance of an earthquake.
For more information please visit earthquake.ca.gov.
Upcoming EEW Advisory Board Meetings
Meeting Notice for the next California Earthquake Early Warning (EEW) Advisory Board
November 3, 2022 1:00 PM
California Governor’s Office of Emergency Services
3650 Schriever Avenue, Building A, MPR 1 & 2
Mather, CA 95655
Zoom Link for the Earthquake Early Warning Advisory Board Meeting
Webinar ID: 812 8804 7696
Or call in:
Participant Call-In Number: +1 669 444 9171
Meeting ID: 812 8804 7696
For information on Earthquake Early Warning (EEW) warnings and alerts, earthquake preparedness, and more: https://earthquake.ca.gov/
For addition details or to contact the program, visit the California EEW Program webpage.
Earthquake Early Warning Basics
Individuals or businesses receiving an alert will vary depending on the distance they are from the epicenter of the earthquake. The closer they are, the shorter the alert time; the further they are, the longer the alert time they will receive.
Earthquake Early Warning Basics
- In an earthquake, a rupturing fault sends out three different types of waves. The fast-moving P-wave is first to arrive, but the damage is caused by the slower S-waves and surface waves.
- Sensors detect the P-wave and immediately transmit data to an earthquake alert center where the location and size of the quake are determined and updated as more data becomes available.
- A message from the alert center is immediately transmitted to users.
- Public Warning – Alert individuals to take protective actions such as Drop, Cover, and Hold On.
- First Responder Mobilization – Open fire station doors for rapid deployment of emergency response equipment and personnel.
- Health Care – Notify medical providers to stabilize and/or stop delicate procedures and maintain critical medical facility operations.
- Utility Infrastructure – Safeguard energy sector grid and other utilities infrastructure for strong shaking with warning alarms and automatic controls to prevent combustions, flooding, and loss of water distribution systems.
- Mass Transit Systems – Prevent fatal collisions or derailments by automatically slowing and/or stopping trains, clearing bridges, and diverting inbound airport traffic.
- Workplace Safety – Employees take protective actions , initiate elevator recall procedures to ground floor, place sensitive equipment in safe mode, secure hazardous materials, and halt production lines to reduce damage.
The earthquake early warning system in California will be able to provide seconds to tens of seconds of alert prior to strong shaking. People may receive a ShakeAlert before, during, or after shaking arrives at their locations. The length of time warning given to any location, before, or after shaking begins depends on a number of factors, including:
- Distance between the epicenter and the closest seismic sensor stations. Generally, the first waves to arrive at a station are the less damaging P-waves that travel 2.5 – 4.5 miles per second on average. The more damaging S-waves travel at approximately 3 miles per second. The closer a station is to the source, the more rapidly the ground motion measurements from an earthquake are identified and the information about the earthquake is sent to the data processing center.
- Data transmission speed over the sensor network from the ground motion sensors to the processing centers for dissemination to end users. Data from multiple stations must be collected and analyzed by the regional seismic networks to issue a warning. Ground motion information must be transferred from each station to the processing center. The existing network utilizes a variety of methods to send data back to the processing center to improve robustness, which includes radio links, phone lines, public/private internet, and satellite links. Delays from packaging and transmitting the data from the station to the processing center and the processing center to the recipient must be reduced to provide useful warning time.
- Geological conditions including type of fault, depth of earthquake event, and geological features in the surrounding areas. Real-time ground motion information received from the stations is used to detect an earthquake and rapidly determine the location and magnitude of the event. Multiple algorithms (a mathematical procedure used to compute a desired result) are used to estimate the earthquake information as rapidly as possible.
- The California Earthquake Early Warning System is based on innovative technology that will improve over time. In rare circumstances, you may receive a ShakeAlert when there was no earthquake.
The California Earthquake Early Warning (EEW) Advisory Board shall convene periodically and advise Cal OES Director Mark Ghilarducci on all aspects of the program, including, but not limited to, the functional areas. The board shall utilize committees, groups, and organizations, including, but not limited to, the California Institute of Technology, the California Geological Survey, the University of California, the United States Geological Survey, and entities participating in the critical infrastructure sectors to fulfill the objectives of the program by supporting the functional areas of the system. The board shall inform the public regarding, and provide the public with the opportunity to engage the board on, the development and implementation of the system. The board shall, in conjunction with the director, determine the appropriate methods to provide the public with an earthquake early warning alert.
- Secretary of Natural Resources Agency
- Secretary of California Health and Human Services
- Secretary of Transportation
- Secretary of Business, Consumer Services, and Housing
- Speaker of the Assembly appointee representing the interests of private businesses.
- Governor’s appointee representing the utilities industry.
- Senate Committee on Rules appointee representing county government.
- Chancellor of the California State University
- President of the University of California
- November 3, 2022
- Public Notice and Agenda for November 3 Meeting
- Public Notice Supplement for November 3 Meeting
- Cal OES EEW Presentation
- Partner Presentation No. 1 – Google
- Partner Presentation No. 2 – USGS
- Partner Presentation No. 3 – UC Berkeley
- Cal OES EEW Fact Sheet – First Responders
- FAQ: How to Become a Technical Partner
- Licensing Pathway Step-by-Step Guide
- USGS ShakeAlert Case Study for Transportation
- June 29, 2022
- October 27, 2021
- August 5, 2020
- March 7, 2019
- September 27, 2018
- April 30, 2018
- November 30, 2017
- June 22, 2017
The CISN collects ground motion data from seismic stations throughout California to rapidly and automatically process this data and produce information about earthquakes occurring. CISN provides this information to the State of California, emergency managers and responders, and to the public and the organization archives the data for use in event review and by scientists and engineers. To learn more about CISN, visit the California Integrated Seismic Network website.
Seismic Station Basics
Seismic sensor set-ups may vary based on the landscape, geological features, telemetry capabilities, and contracted partners’ equipment experience.
Seismic stations include 4 major elements:
- Seismic Sensor – all cases in accelerometers (that measure larger ground motion) and some cases include a seismometer (that are more sensitive but cut off larger ground motion).
- Data logging collector and storage unit.
- Power system (which may include solar panels).
- Telemetry equipment to transmit data to the CISN processing centers.
Earthquake Early Warning Seismic Sensor Status
The statewide seismic instrumentation build out has been fully funded, in large part due to the over $75 million in State General Funds over five budget cycles.
As of March 2022, more than 78 percent of the statewide seismic network has been installed. The remaining 22 percent, focused in the less densely populated areas, and is scheduled to be fully installed and completed no later than June 2025.
The vision for the earthquake early warning system in California was articulated in the May 2016 California Earthquake Early Warning System Project Implementation Framework (the Framework). The framework set a target of 1,115 seismic sensors state wide to achieve the optimum sensor density spacing for earthquake early warning. To maximize warning time and minimize the “delayed notification zone” (the area close to the earthquake epicenter that will likely receive a notification after shaking occurred), stations must be located near active faults. The current goal is to operate a network of seismic stations that are spaced no more than 20-km apart and within 5-km of all mapped fault traces. However, experience tells us that damaging earthquakes can occur even where faults have not been mapped (e.g., 1994 Northridge earthquake); therefore, 20-km spacing or closer is also needed throughout all high-risk areas. A denser station spacing of about 10-km is needed to minimize the delayed notification zone in more densely populated areas.
Visit the Core CISN/CEEWS Partners and learn more at:
Research & Development
What is Research and Development (R&D) in regards to Earthquake Early Warning?
Earthquake early warning enables individuals to take protective actions, such as drop, cover, and hold on, and it can notify delicate-process facilities that may want to slow or stop sensitive operations to mitigate damage. R&D activities focus on establishing rapid alert dissemination channels and technologies and then integrating them into California’s infrastructure and industries.
Challenges to Full Implementation
A key consideration for R&D in the CEEWS design is “latency”, the time it takes to detect, characterize, and model earthquakes, and to deliver targeted alert messages to people at risk from impending earthquake shaking.
Historically, public alerting systems have been engineered for reliability and reach, but the speed of operation has rarely been considered a design priority. During the Cold War, the Emergency Alert System (EAS) was designed with the intent to disseminate a Presidential broadcast within 15 minutes. Local alerts, such as those from the National Weather Service (NWS), can presently deliver messages in a matter of minutes.
Earthquake early warnings are special because alert generation and delivery must occur within three seconds of the earthquake being detected.
Current Projects Under Development
One method under development to improve latency is datacasting (data broadcasting). Datacasting utilizes extra bandwidth in digital TV signals and is currently used to transmit news, weather, traffic, and stock market information that may or may not be related to the program on TV at the time. This information can also be used to broadcast earthquake early warnings which can be utilized by companies and individuals with specialized receiver equipment. Datacasting is a robust, high speed data delivery method that can provide an alternative to other methods like phone and internet.
Education & Outreach
Tools & Resources
Get alerts on your phone
Prepare for an earthquake
See the latest earthquakes
Report an earthquake you felt
Learn more about our partners
- USGS ShakeAlert
- Berkeley Seismology Lab
- Caltech Seismological Laboratory
- California Geological Survey
- California Integrate Seismic Network
Learn more about earthquake early warning
The California Governor’s Office of Emergency Services has received more than $75 million from the California Legislature. Most recently, Governor Newsom’s 2021-22 budget, which was passed by the Legislature and signed into law included $17.3 million to complete the infrastructure buildout and fund the remaining activities identified in the initial CEEW System Business Plan.
Earthquake Early Warning Financial Information
- 2022 Business Plan Update – California EEW Program Annual Business Plan 2022 Update
- 2021 Business Plan Update – California EEW Program Annual Business Plan 2021 Update
- Implementing Earthquake Early Warning in California – California EEW Business Plan