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E-larmS: Earthquake early warning algorithm
Basics |
ShakeAlert |
Timeline |
Japan |
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Key Publications
E-larmS |
G-larmS |
T-larmS |
MyShake
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E-larmS is an earthquake early warning algorithm that has been developed and implemented by the UC Berkeley Seismological Laboratory.
It is a core algorithm generating the alert messages issued by ShakeAlert.
E-larmS development started in 2001, real-time testing in California began in 2007, and delivery of alerts to test users began in 2011.
E-larmS is part of ShakeAlert and now provides alerts to test users in California, Oregon and Washington. E-larmS is also being tested on the real-time networks in Chile, Israel, Korea and Turkey.
Technical details about the system can be found in our publications
Press coverage of the system is on the press page
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August 24, 2014
M6.0 South Napa Earthquake:
ShakeAlert issues warning, alert from ElarmS
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The above is a video capture of the warning received at the UC Berkeley Seismological Laboratory. It shows the 5 second countdown to the beginning of shaking in Berkeley and the expected shaking intensity in Berkeley which was 4 (shown IV) on the intensity scale and described as "light" shaking. The strongest shaking in Berkeley occured 10 seconds after the alert was received.
Warning time: The amount of warning time depends on the distance of the user from the epicenter of the quake; the greater the distance, the greater the warning time. For the Napa quake Berkeley got 5 sec warning, our users in San Francisco got 8 sec warning.
User actions: Our beta-testers across the San Francisco Bay Area received the alert at the same time as the Berkeley Seismo Lab. BART has implemented an automated train-stopping system. The system activated and would have stopped trains, however, at 3:20 in the morning there were no trains running. The alert was received in the 911 center in San Francisco and the the UC Police.
Press covereage following the alert,
and subsequent
calls for a public system
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March 28, 2014
M5.1 La Habra Earthquake:
ShakeAlert issues warning across LA, alert from ElarmS
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ElarmS provided the ShakeAlert for the M5.1 La Habra quake, the M4.4 Encino quake beneath the Santa Monica mountains (March 17, 2014) and the M4.2 Westwood quake (June 2, 2014), all in the Los Angeles region.
The above video shows a press conference at Caltech follwoing the La Habra quake. During the press conference ShakeAlert issues a warning for a small aftershock that is caught on camera.
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First ElarmS Users Group Meeting
The first ElarmS users workshop was held at UC Berkeley from May 5-16, 2008. Participants came from South Korea, Germany, Switzerland, Puerto Rico and Hawaii. Participants shown: Richard Allen, Holly Brown, Marta Caprio, Heon Cheol Chi, Barry Hirshorn, Harold Irizarry, Geunyoung Kim, Nina Koehler, Stuart Koyanagi, Duk Kee Lee, Se Jong Lee, Yong Cheol Park, Jung Ho Park, DongHoon Sheen.
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Probabilistic warning times in the San Francisco Bay Area
Using our knowledge of future likely earthquakes in northern CA and combining it with the time required by the ElarmS methodology to provide a warning, we can estimate the range of warning times that such a system could provide.
This work is presented in
Allen, Seismo. Res. Lett., 77 (3), 371-376,2006.
The e-supplement
contains warning times for different regions of the Bay Area.
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The deterministic nature of earthquake rupture
The predominant period, tau-p-max, of the first few seconds of the P-wave from 71 earthquakes around the world with magnitudes ranging from 3.0 to 8.3 are measured. We find that tau-p-max scales with the magnitude of the earthquake despite the fact that the rupture is not complete by the time of the measurements for all events greater than M 4.0. We interpret this observation as suggesting that earthquake rupture is deterministic.
This work is presented in
Olson and Allen, Nature, 438, 212-215,2005.
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The potential for earthquake early warning
Using the existing seismic network in southern California and a dataset of past earthquakes, a methodology for rapid magnitude estimation of earthquakes is developed using the frequency content of the first few seconds of the P-wave.
Given the accuracy and timeliness of the earthquakes information we suggest that it would be feasible to develop a warning system in the region.
This work is presented in
Allen and Kanamori, Science, 300, 786-789, 2003.
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Acknowledgements
Support for the earthquake early warning efforts at UC Berkeley is provided by:
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