ShakeAlert—An Early Warning System for the United States West Coast

First Felt W ave Damag ing W av Fault es Sensors positioned Earthquake about 6-12 miles apart Sensors alert center Epicenter

S-wave P-wave Epicenter

Earthquake early warning systems like ShakeAlert work because the warning message can be transmitted almost instantaneously, whereas the shaking waves from the earthquake travel through the shallow layers of the Earth at speeds of one to a few kilometers per second (0.5 to 3 miles per second). This diagram shows how such a system would operate. When an earthquake occurs, both compressional (P) waves and transverse (S) waves radiate outward from the epicenter. The , which travels fastest, trips sensors placed in the landscape, causing alert signals to be sent ahead, giving people and automated electronic systems some time (seconds to minutes) to take precautionary actions before damage can begin with the arrival of the slower but stronger S waves and later-arriving surface waves. Computers and mobile phones receiving the alert message calculate the expected arrival time and intensity of shaking at your location. USGS image created by Erin Burkett (USGS) and Jeff Goertzen (Orange County Register). pose a serious risk How Do Earthquakes and Early arthquake early warning to our Nation. According to the Fed- Warning Systems Work? systems use earthquake science eral Emergency Management Agency E An earthquake occurs when a fault and the technology of monitoring (FEMA), 77 percent of that risk, or an in the Earth’s crust breaks suddenly systems to alert devices and people average annual loss of $4.1 billion, is and the two sides move relative to one when shaking waves generated by concentrated on the West Coast in Cali- another. The rupture begins at one point an earthquake are expected to ar- fornia, , and (Federal on the fault and rapidly extends along rive at their location. The seconds Emergency Management Agency, 2008). some distance of the fault, like a length- to minutes of advance warning can Growing urbanization and increasing ening crack in a car windshield. As the allow people and systems to take reliance on complex infrastructure for rupture travels along the fault, the sudden actions to protect life and property power, water, telecommunication, and movement of the two sides of the fault from destructive shaking. The transportation magnify that risk. An generates seismic (shaking) waves that United States Geological Survey earthquake early warning system that radiate outward through the Earth—much (USGS) in collaboration with can rapidly detect earthquakes and send like ripples from a stone dropped in several partners has been working alerts could prompt actions to protect water. It is these waves that cause the to develop an early warning system life and property before strong shaking ground shaking you can feel and the dam- for the United States. ShakeAlert, arrives. Development of such a system is age and destruction during earthquakes. a demonstration system currently a critical step toward offsetting physical Although no one can predict earth- under development, is designed to risks, improving public understanding of quakes, the technology exists to provide cover the West Coast States of Cali- earthquake hazards, and reducing fear of some warning to surrounding communi- fornia, Oregon, and Washington. the unknown and unpredictable nature of earthquakes. ties once a quake begins. This is done U.S. Department of the Interior Fact Sheet 2014–3083 U.S. Geological Survey August 2014 States Geological Survey (USGS) and How Warning Can Increase university partners has been developing 5 Safety and Prevent Damage and testing ShakeAlert, an early warning Seattle system for earthquakes along the West Even a few seconds of warn- Coast of the United States. ing can enable actions that protect 3 people and property. In the time be- How Does ShakeAlert Work? Portland tween receipt of an alert and arrival of damaging shaking, the following ShakeAlert is a demonstration early actions can be taken: warning system that began sending alerts EXPLANATION to test users in in January 2012 1 Human Responses Scenario (see www.shakealert.org). The system M8 earthquakes • Public: Citizens, including with magnitude detects earthquakes using the California schoolchildren, drop, cover, and Major fault lines Integrated Seismic Network (CISN), hold on; turn off stoves, safely 1 Minutes of warning an existing network of about 400 high- M9 stop vehicles. Seismic sensor quality ground motion sensors. CISN is • Businesses: Personnel move to M8 a partnership between the U.S. Geologi- safe locations. cal Survey (USGS), State of California, • Medical services: Surgeons, California Institute of Technology, and dentists, and others stop deli- Sacramento University of California, Berkeley, and 1 cate procedures. is one of seven regional networks that • Emergency responders: Open make up the Advanced National Seismic 2 firehouse doors, personnel System. ShakeAlert extends CISN’s prepare and prioritize response current research and post-earthquake decisions. response products and takes advantage Automated responses of our Nation’s existing infrastructure • Businesses: Open elevator for earthquake monitoring. When fully 2 0 50 MILES doors, shut down production operational, ShakeAlert will be able to 0 50 100 KILOMETERS lines, secure chemicals, place 1 distribute alerts through all available sensitive equipment in a safe distribution channels, including FEMA’s Earthquake Hazard Levels Percent of 1g shaking with M8 mode. Wireless Emergency Alert system and 2-percent probability of being exceeded in 50 years. • Transportation: Automatically Integrated Public Alert and Warning slow or stop trains to prevent 0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80 > 80 System, smartphone apps, social media derailment. providers, and other electronic alert tech- Map of the United States West Coast • Power infrastructure: Protect nologies as they develop. showing the amount of advance warning power stations and grid facilities Test users of ShakeAlert receive time that might be available from a system from strong shaking. alerts through the demonstration user like ShakeAlert for several plausible future interface, a computer application with earthquake scenarios. Those scenarios both audible and visual alert features. include magnitude 8 (M8) quakes on the After ShakeAlert detects an earthquake, a with epicenters in by an earthquake early warning system, map pops up on the user’s screen to show northern and southern California and an M9 which rapidly detects seismic waves as an the location of the earthquake epicenter quake on the earthquake happens, calculates the maxi- (the point on the surface directly above with an epicenter offshore of northernmost mum expected shaking, and sends alerts the quake’s starting point) and of waves California. Major population centers could to electronic systems and devices before moving toward the user; also shown is have as much as several minutes warning damaging waves arrive. Early warning is the time remaining until waves will reach before shaking waves from those quakes possible because information can be sent the user’s location and cause the indi- struck them. The map also shows the through communication systems virtually cated intensity of shaking. An alert sound regional variation in the level of earthquake instantaneously, whereas seismic waves alternates with a voice that counts down hazard in terms of the intensity of shaking travel through the shallow Earth at speeds to the arrival time of seismic waves and (as a percentage of g, the acceleration ranging from one to a few kilometers per announces the expected intensity. of gravity) having at least a 2-percent second (0.5–3 miles/sec). This means probability of being exceeded in a 50-year that the shaking can take some seconds How Much Warning is Possible? period (from 2014 USGS hazard map). The or even minutes to travel from where the An early warning system like network of seismic (earthquake) sensors is earthquake occurred to where you are. ShakeAlert can provide seconds to more concentrated near major faults and Thus it is possible for automated minutes of warning before strong shak- population centers. Illustration modified systems or even your personal elec- ing arrives. The amount of warning time from Allen (2013). tronic devices, such as smartphones, depends on the speed of the warning sys- to receive an alert before destructive tem and your distance from the epicenter. shaking arrives. A coalition of the United A good system requires a dense network of sensors to ensure that there are enough • Quick and robust telecommunication arrived from the South Napa earth- of them near all possible earthquake from sensors quake, and users in Pasadena, California, sources. Such a dense network can reduce • Computer algorithms to quickly received about 6 seconds of warning for the area near the epicenter for which estimate an earthquake’s location, the La Habra earthquake. reliable warning is not possible because magnitude, and fault rupture length, The ShakeAlert system is still in the the earthquake source is too close for an and to map resulting intensity demonstration phase. USGS has pub- alert to outpace the seismic waves. The • Quick and reliable mass notifications lished an implementation plan spelling farther a location is from the epicenter, • End users educated in how to use the out the steps needed to complete the the greater the possible amount of warn- alerts system and begin issuing public alerts ing time. To maximize warning time, (Given and others, 2014). Before it can the system must minimize delays in data Future Developments be released to the public and be set up processing, communication, and delivery to trigger automated actions, it requires Although few notable earthquakes of alerts. additional development and further test- have occurred since ShakeAlert began ing to make it sufficiently reliable (see Major Components of an Early testing, the system has successfully pro- sidebar “How Warning Can Increase vided warnings to test users during such Warning System Safety and Prevent Damage”), as well as earthquakes as the M5.1 La Habra earth- end-user education on how to understand quake on March 28, 2014, and the M6.0 The ability to send adequate warning and use alerts. South Napa earthquake on August 24th, before shaking arrives depends on: The successful completion of the • A network of sensors that are densely 2014. Test users in Berkeley, California, system will require the coordinated spaced and close to faults received alerts 5 seconds before shaking efforts of government agencies at all

San Andreas Fault

Why ShakeAlert Emphasizes Intensity, not Magnitude Will the West Coast have an The shaking you feel is Early Warning System Before or described by earthquake intensity After the Next Big Quake? rather than magnitude. High in- 10 Seconds Most countries with early tensities are what cause damage N warning systems built them after a in earthquakes. devastating earthquake. Intensity Japan invested $600 million in • represents the level of shaking such a system after the 1995 Kobe caused by earthquake waves earthquake killed 6,400 people. at a particular location Today, Japan’s system allows every • depends on magnitude + dis- citizen to receive advance alert of earthquake ground shaking from tance + local geology 50 Seconds • varies from place to place in a N the Japan Meteorological Agency. single earthquake Thanks to this system, no trains derailed in the 2011 magnitude 9.0 Magnitude Tohoku earthquake, and according • is one number representing the to a poll in Japan, 90 percent of the amount of energy released in citizens think the system is worth an earthquake the investment (Fujinawa and Noda, • depends on the size (surface 2013). area) of fault rupture 90 Seconds N Other countries that built sys- ShakeMaps (Wald and tems after devastating earthquakes others, 2003) rapidly show the Diagrammatic maps showing include: distribution of intensity after an northwestward spreading of ground shaking • China (after the 2008 Wenchuan earthquake (http://earthquake.usgs. (red and yellow) generated by the M7.8 Earthquake killed 87,587 people) gov/earthquakes/shakemap/). ShakeOut scenario earthquake centered in • Taiwan (after the 1999 Chi Chi You can also report the the Imperial Valley of southern California. Earthquake killed 2,415) ground shaking you experienced The times shown are times after the start • Turkey (after the 1999 Izmit to help create intensity maps of the earthquake rupture at the epicenter Earthquake killed 17,127) through Did You Feel It (http://earth- (white star). This scenario was part of • Mexico (after the 1985 Mexico quake.usgs.gov/earthquakes/dyfi/). a comprehensive earthquake exercise City Earthquake killed 10,153) conducted in the State of California in 2008 (Perry and others, 2008). levels, private companies, and the public. California recently committed to develop- ing earthquake early warning statewide, and companies are beginning to develop products to use and distribute the alerts. The ongoing work of USGS scien- tists, together with partner organizations, on earthquake early warning systems 3 is only part of the National Earthquake Hazard Reduction Program’s efforts to 2 safeguard lives and property from the future quakes that are certain to strike along the West Coast and other areas of 4 1 the United States. S-wave P-wave 6 References 5 7 Allen, R., 2013, Seismic hazards; sec- onds count: Nature, v. 502, no. 7469, On your screen: ShakeAlert accessed 2014 at: http://www.nature. com/news/seismic-hazards-seconds- 1 Real-time tracking of seismic waves from quake’s epicenter. count-1.13838. 2 Real-time tracking of the fault rupture (updates intensity). Federal Emergency Management Agency, 3 Your current location tracked by GPS. 2008, FEMA 366; HAZUS-MH esti- 4 Seconds remaining before seismic waves reach you. mated annualized earthquake losses for 5 the United States: Federal Emergency Expected intensity of quake at your current location. Management Agency, accessed 2014 at 6 Estimated magnitude of quake. https://www.fema.gov/media-library/ 7 Intensity scale. assets/documents/13293?id=3265.

Fujinawa, Y., and Noda, Y., 2013, Japan’s A user of ShakeAlert receives a message like this on the screen of his computer. The earthquake early warning system on 11 message alerts the user to how many seconds before the shaking waves arrive at their March 2011—Performance, shortcom- location and the expected intensity of shaking at that site. The shaking intensity follows the ings, and changes: Earthquake Spectra, Modified Mercalli scale; an intensity of VI, as shown here, would mean the shaking is felt v. 29, no. S1, p. S341–S368, doi: http:// by everyone, people find it difficult to stand, and structures may suffer some damage. The dx.doi.org/10.1193/1.4000127. warning message also displays a map with the location of the epicenter, the magnitude of the quake, and the current position of the P and S waves. In this example, the alert is for the Given, D.D., Cochran, E.S., Heaton, ShakeOut scenario earthquake (Perry and others, 2008). T., Hauksson, E., Allen, R., Hellweg, P., Vidale, J., and Bodin, P., 2014, Technical implementation plan for the Wald, D., Wald, L., Worden, B., and ShakeAlert production system—An Goltz, J., 2003, ShakeMap—A tool for For more information contact: U.S. Geological Survey earthquake early warning system for earthquake response: U.S. Geological Survey Fact Sheet 087-03, 4 p., [Also Earthquake Hazards Program the West Coast of the United States: Earthquake Early Warning U.S. Geological Survey Open-File available at http://pubs.usgs.gov/fs/ http://earthquake.usgs.gov/research/ Report 2014–1097, 25 p., http://dx.doi. fs-087-03/.] earlywarning/ org/10.3133/ofr20141097. or Erin R. Burkett, Douglas D. Given, and Perry, S., Cox, D., Jones, L., Bernknopf, Lucile M. Jones Erin R. Burkett [email protected] R., Goltz, J., Hudnut, K., Mileti, D., Edited by Peter H. Stauffer This Fact Sheet and any updates to it Ponti, D., Porter, K., Reichle, M., Layout by Vivian Nguyen Seligson, H., Shoaf, K., Treiman, J., are available online at: http://pubs.usgs.gov/fs/2014/3083/ and Wein, A. 2008, The ShakeOut COOPERATING ORGANIZATIONS earthquake scenario—A story that California Geological Survey Southern Californians are writing: U.S. California Institute of Technology Geological Survey Circular 1324, 16 p. California Office of Emergency Services [Also available at http://pubs.usgs.gov/ The Moore Foundation circ/1324/.] Southern California Earthquake Center

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