Earthquake Advisory

Earthquake, Tsunami & Volcano Programs



Frequently Asked Questions



What is an Earthquake Advisory?

An Earthquake Advisory is a statement that summarizes the scientific evaluation of the California Earthquake Prediction Evaluation Council (CEPEC) regarding the short-term elevated likelihood of a damaging earthquake. The Advisory provides Cal OES' recommendations for response actions by local emergency services and measures that the public can take for disaster preparedness.


When is an Earthquake Advisory issued?

Advisories are issued following earthquakes in which there is concern about the potential for subsequent damaging earthquakes. The basis of the advisory is existing knowledge of seismic history and potential of the area under consideration.


How is an Earthquake Advisory developed and written?

Cal OES issues advisories only after notification from CEPEC of special concern regarding an evolving sequence and where, in Cal OES’ judgment, there are significant public safety considerations. In the immediate aftermath of significant seismic activity, the Cal OES Director can request that CEPEC evaluate the event and advises on the next steps.
After CEPEC meets to discuss the history and current data regarding a specific situation, the chairperson then provides those details to Cal OES which in turn interprets the summarization of those findings and determines if an advisory is warranted.
Cal OES then notifies the affected county emergency managers per Operational Area notification protocols. Once in agreement, an advisory is then distributed to educate the public.


What is an Earthquake Advisory intended to do?

The purpose of the Earthquake Advisory is to provide scientific information to emergency managers and the public for low-probability, high-consequence events and serve as the basis for recommended preparedness and mitigation actions by emergency management officials to those communities in the areas of concern. Specifically, the Advisory intends to inform the public to consider actions such as: build a preparedness kit; review communication and emergency disaster plans; and practice the “Drop, Cover and Hold On” drill.
The Advisory also encourages local government to publish disaster readiness information, revisit local emergency plans and check supplies and test equipment.


Does California issue “alerts and warnings”?

Yes. Each jurisdiction within the state is responsible for preparing for a disaster, including establishing methods for alerting and warning the public, mobilizing resources and initiating protective actions. At the state level, Cal OES operates the California State Warning Center (CSWC), which is staffed 24 hours a day, 365 days a year to serve as the official state level point of contact for emergency notifications. From this center, Warning Center personnel maintain contact with County Warning Points, state agencies, federal agencies and the National Warning Center in Berryville, Virginia.


Is an Earthquake Advisory considered part of the alert and warning system?

No. The CSWC receives notification of earthquakes from the California Integrated Seismic Network (CISN), National Earthquake Information Center and the United States Geological Survey. CISN is a statewide network that provides the basic information for California earthquakes shown on the CISN Display. The CISN Display is an Internet-based rapid earthquake notification system that receives earthquake information from networks world-wide. The CSWC is responsible for informing, communicating, alerting and notifying local governments, Operational Areas and state officials and the Federal Government of natural or human caused emergencies.
To meet this responsibility, the Warning Center is equipped with a number of telephone, data and radio systems, including the California Warning System, California Law Enforcement Telecommunications System, NWS Weather Wire, CSWC message switching computer, Emergency Digital Information Service, CISN and Dialogic Automated Notification System. Most of these systems are used on a day-to-day basis; others are available for use in an emergency, as conditions require.


Does Cal OES issue earthquake advisories the same way as tsunami watches and warnings are issued by the National Weather Service?

No. An Earthquake Advisory is not equivalent to a tsunami watch or warning, in fact the process is quite different, because the likelihood of an event is less certain. Earthquakes remain unpredictable, even following a potential foreshock, an event is still improbable. Earthquake advisories can only provide emergency managers and the public with uncertain scientific information, but that information can still mitigate the impacts of a potential major earthquake.


Why does Cal OES send an Earthquake Advisory to local government agencies first?

One of the key goals of the Earthquake Advisory is to provide as much available scientific data as possible to formulate appropriate precautions and preventative actions for emergency managers within local government.


How often does Cal OES issue earthquake advisories?

Cal OES began issuing advisory statements in 1985 following earthquakes where the California community of seismologists believed could generate other earthquakes that could put the public at risk. Since 1991, there have been 11 earthquake advisories issued.


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