California tests state-wide earthquake early warning
November 5, 2019
The first state-wide public test of California’s early earthquake warning system took place last month using the US Geological Survey’s (USGS) ShakeAlerts early warning alerts.
Alerts are delivered by two independent methods, first over the federal WEA wireless emergency alert system and, secondly, through the University of California Berkeley’s MyShake smartphone app.
"Today we commemorate the 30th anniversary of one of our nation’s most destructive earthquakes, the magnitude 6.9 Loma Prieta quake,” said USGS director Jim Reilly. “That event also marked the first deployment of an early forerunner of the ShakeAlert system, which was used to warn rescue workers about potentially dangerous aftershocks. Now, starting across the state of California, ShakeAlert is powering the nation’s first-ever state-wide public earthquake early warning system that could be expanded to provide an early warning benefit for all citizens living in earthquake country.”
The choice when issuing earthquake warnings is first to issue alerts for weak shaking and potentially provide long warning times, but risk sending alerts for the many events that do not go on to produce damaging ground shaking or, secondly, issue alerts only when ground shaking is expected to be damaging, with the trade-off that the alert will be sent much later, reducing the amount of time available to take action.
USGS is starting delivery of ShakeAlert data through FEMA’s integrated public alert and warning system, which is used to deliver amber and weather alerts to mobile phones via the WEA system operated by cellular companies. USGS and its partners have tested this alert delivery pathway and are working continuously to improve the speed of ShakeAlert delivery to wireless devices.
ShakeAlerts will be sent through WEA to those state-wide who could experience potentially damaging shaking from magnitude five or greater quakes. As the seismic network is expanded and the ShakeAlert system and modes for communicating the alerts are further developed and tested, the speed, reliability and public use of ShakeAlerts should also increase.
The MyShake app, which was developed by the University of California, Berkeley, and funded by the state of California and the Moore Foundation, will also send alerts to people who could feel shaking due to magnitude 4.5 or greater earthquakes.
This public testing phase for MyShake and WEA alerts is enabled by upgrades to, and increases in the density of, seismic networks and data analysis systems across the US west coast. USGS has been working with state emergency managers, universities and more than 60 pilot partners who now have systems actively using USGS-generated ShakeAlerts to develop products that protect lives and property.
The USGS and its partners will be closely monitoring the performance of all delivery pathways that use ShakeAlert data and will work to improve alerting speeds and identify opportunities for further developments.
“USGS and its partners are making considerable progress with the build-out of the sensor network that underpins ShakeAlert,” said David Applegate, USGS associate director for natural hazards. “More than half of the 1675 sensors needed to complete the west coast system as designed have been installed and are operating, with the emphasis so far on installations near population centres.”
Depending on a user’s location, alerts may provide seconds to tens of seconds of warning before the user feels shaking from an earthquake that may affect them, though there will be users near the epicentre who do not receive the alert before they feel shaking.
“This will often happen when a user is within a few tens of miles of the earthquake’s epicentre because of the time it takes to characterise an earthquake’s size and likely shaking levels, as well as delays resulting from the technologies our partners use to deliver the alert,” said USGS chief scientist Jeff McGuire.
McGuire emphasised that the speed of alert delivery would vary among users and also for the same user receiving ShakeAlerts through different mechanisms.
“For example,” said McGuire, “the speed could be as short as a few seconds for apps like MyShake or significantly longer through the WEA system, and some users may not receive a WEA alert at all for a particular earthquake. The delivery technologies will hopefully get faster over time.”
ShakeAlerts and the delivery applications being developed by partners do not replace the need for people to plan for earthquakes by taking appropriate preparedness steps and mitigating the risk. When someone receives an alert, they should act quickly to take a protective action such as drop, cover and hold on. They should not wait to feel the shaking.
USGS is building the ShakeAlert earthquake early warning system in California, Oregon and Washington as a new tool being delivered by the Advanced National Seismic System. The enhanced sensor networks being built out for ShakeAlert will improve many existing ANSS information products.
USGS ShakeAlert pilot partners in those states already use ShakeAlerts to trigger automated actions for critical infrastructure, including water conveyance systems and mass transit lines. Public alerting in Oregon and Washington will begin as soon as the sensor network is sufficiently built out and the citizens in those states can be educated about the system.
ShakeAlert partners are selected organisations or companies that helped develop the seismic networks and data analysis systems that make ShakeAlert possible, or who can demonstrate the use of ShakeAlerts to reduce injuries or losses.
In California, USGS institutional partners include the California Governor’s Office of Emergency Services, California Institute of Technology, University of California Berkeley, California Geological Survey, Gordon & Betty Moore Foundation, University of Nevada, Reno, and the city of Los Angeles.
In Oregon and Washington, key institutional partners are the Washington Emergency Management Division, University of Washington, University of Oregon, Oregon Office of Emergency Management and each state’s geological survey. The USGS has also conducted a feasibility study of deploying ShakeAlert in Alaska.
Earthquakes are a nationwide problem with more than 143 million people exposed to potentially damaging shaking in the USA. Fifty million of those people are in California, Oregon and Washington.
The picture shows students participate in the Great Southeast ShakeOut earthquake drill at Langston Hughes Middle School in Reston, Virginia. They are conducting the drop, cover and hold on safety procedure. The picture was taken by Jessica Robertson from USGS.