USGS is actively pursuing research in earthquake early warning.
How the ShakeAlert® System Works
DETECT, DELIVER, PROTECT: ShakeAlert® is not earthquake prediction. Rather, the USGS-operated ShakeAlert Earthquake Early Warning system detects an earthquake that has already started and estimates its location, magnitude and shaking intensity. If an earthquake becomes large enough to meet USGS alert thresholds, a ShakeAlert Message is issued. Then, technical partners, which have entered into a license agreement with the USGS, use this information produce and deliver an alert that prompts people to take a protective action, such as DROP, COVER, AND HOLD ON, and/or to trigger an automated action that can protect vital systems, equipment, facilities, and infrastructure. These automated actions could include slowing a train, closing valves, issuing a public announcement, and many others.
The ShakeAlert system takes a network approach to earthquake detection and alerting. This network uses sensors distributed over a wide area where earthquakes are likely to occur on the West Coast of the United States (with nearly 1,700 anticipated on network build-out). Data from individual sensors across large regions are combined to maximize accuracy and alerting time during moderate-to-large earthquakes.
During an earthquake, a rupturing fault produces several different kinds of waves that carry energy away
from the epicenter like ripples from a rock thrown into a pond. The fastest-moving seismic waves (primary or P-waves) travel about 3.7 miles per second and generally do not produce strong shaking. P-waves are followed by slower moving, and generally more damaging waves (secondary or S-waves) and surface waves that travel about 2.5 miles per second. The ShakeAlert sensor network detects earthquakes quickly, and immediately transmits data to a ShakeAlert Processing Center, where estimates of the location, size, and shaking intensity of the earthquake are determined in a matter of seconds.
Technical Partners are integral to the ShakeAlert System because they are responsible for producing and delivering ShakeAlert-powered alerts to people and critical systems. Technical Partners span multiple industries and sectors, and include private for-profit companies, public entities, and nonprofits that can benefit from becoming part of the ShakeAlert System.
ShakeAlert works because:
- P-waves travel almost twice as fast as the damaging S-waves and surface waves; and
- The speeds of today’s data telecommunications systems are many times faster than seismic waves. Both of these factors make it possible for ShakeAlert-powered alerts to reach people before shaking arrives. Because of the speed difference between P-waves, S-waves, and surface waves, someone who is farther from the earthquake’s origin has more time to potentially receive an alert before shaking arrives.
ShakeAlert®-Powered Alert Delivery Levels
If an earthquake becomes large enough to meet USGS alert thresholds, a ShakeAlert Message is issued. ShakeAlert technical partners use this information to produce and deliver alerts that rapidly prompts people to take a protective action, such as DROP, COVER, AND HOLD ON, and/or to trigger an automated action that can protect vital systems, equipment, facilities, and infrastructure. These automated actions could include slowing a train, closing valves, issuing a public announcement, and many others.
For example, cell phone app providers and Android can deliver ShakeAlert-powered alerts to people who could feel weak shaking (Modified Mercalli Intensity - MMI III) or greater for earthquakes M4.5 and larger. For people who could feel moderate shaking (MMI V) or greater Android delivers alerts with more urgent language.
The Modified Mercalli Intensity (MMI) Scale is composed of increasing levels of intensity that range from imperceptible shaking to catastrophic destruction; levels of intensity are designated by Roman numerals. The MMI Scale does not have a mathematical basis; instead, it is a holistic ranking based on observed effects. The lower range of the MMI scale generally deals with the manner in which the earthquake is felt by people. The higher range considers observed structural damage.
For More Information:
Earthquake early warning for estimating floor shaking levels of tall buildings
The impact of 3D finite‐fault information on ground‐motion forecasting for earthquake early warning
Evidence-based guidelines for protective actions and earthquake early warning systems
Expected warning times from the ShakeAlert earthquake early warning system for earthquakes in the Pacific Northwest
Commentary: The role of geodetic algorithms for earthquake early warning in Cascadia
Earthquake early warning in Aotearoa New Zealand: A survey of public perspectives to guide warning system development
Developing post-alert messaging for ShakeAlert, the earthquake early warning system for the West Coast of the United States of America
ShakeAlert Earthquake Early Warning System Performance During the 2019 Ridgecrest Earthquake Sequence
The potential of using dynamic strains in earthquake early warning applications
Practical limitations of Earthquake Early Warning
Earthquake early warning ShakeAlert 2.0: Public rollout
Estimating rupture dimensions of three major earthquakes in Sichuan, China, for early warning and rapid loss estimates
How do I sign up for the ShakeAlert® Earthquake Early Warning System?
How do I sign up to receive ShakeAlert®-powered Alerts on my phone? Provider Type Apple Store/Google Play Link States USGS/FEMA Wireless Emergency Alerts N/A FEMA | WEA CA/OR/WA MyShakeTM Mobile App Y/Y MyShake CA/OR/WA QuakeAlertUSA Mobile App Y/Y QuakeAlertUSA CA/OR Google Android Operating System N/A Google CA/OR/WA San Diego Emergency (SD Emergency) with ShakeReadySD Mobile App Y/Y Ready San...
Can I get on a list to receive an email message when there is an earthquake? How do I sign up for earthquake notifications? Are there any Feeds I can subscribe to?
Please go to the USGS Earthquake Notification Services (ENS) to sign up for free emails or text messages to your phone. Use the default settings or customize ENS to fit your needs. Also check out the many different Earthquake Feeds. ENS is NOT an earthquake early warning system. Messages issued by ENS will almost always arrive after you would feel any shaking. Learn more: How do I sign up for...
- Overview
USGS is actively pursuing research in earthquake early warning.
How the ShakeAlert® System Works
DETECT, DELIVER, PROTECT: ShakeAlert® is not earthquake prediction. Rather, the USGS-operated ShakeAlert Earthquake Early Warning system detects an earthquake that has already started and estimates its location, magnitude and shaking intensity. If an earthquake becomes large enough to meet USGS alert thresholds, a ShakeAlert Message is issued. Then, technical partners, which have entered into a license agreement with the USGS, use this information produce and deliver an alert that prompts people to take a protective action, such as DROP, COVER, AND HOLD ON, and/or to trigger an automated action that can protect vital systems, equipment, facilities, and infrastructure. These automated actions could include slowing a train, closing valves, issuing a public announcement, and many others.
The ShakeAlert system takes a network approach to earthquake detection and alerting. This network uses sensors distributed over a wide area where earthquakes are likely to occur on the West Coast of the United States (with nearly 1,700 anticipated on network build-out). Data from individual sensors across large regions are combined to maximize accuracy and alerting time during moderate-to-large earthquakes.
ShakeAlert 3 Basic Steps: Sensor Networks to processing center to users. During an earthquake, a rupturing fault produces several different kinds of waves that carry energy away
from the epicenter like ripples from a rock thrown into a pond. The fastest-moving seismic waves (primary or P-waves) travel about 3.7 miles per second and generally do not produce strong shaking. P-waves are followed by slower moving, and generally more damaging waves (secondary or S-waves) and surface waves that travel about 2.5 miles per second. The ShakeAlert sensor network detects earthquakes quickly, and immediately transmits data to a ShakeAlert Processing Center, where estimates of the location, size, and shaking intensity of the earthquake are determined in a matter of seconds.
Technical Partners are integral to the ShakeAlert System because they are responsible for producing and delivering ShakeAlert-powered alerts to people and critical systems. Technical Partners span multiple industries and sectors, and include private for-profit companies, public entities, and nonprofits that can benefit from becoming part of the ShakeAlert System.
ShakeAlert works because:
- P-waves travel almost twice as fast as the damaging S-waves and surface waves; and
- The speeds of today’s data telecommunications systems are many times faster than seismic waves. Both of these factors make it possible for ShakeAlert-powered alerts to reach people before shaking arrives. Because of the speed difference between P-waves, S-waves, and surface waves, someone who is farther from the earthquake’s origin has more time to potentially receive an alert before shaking arrives.
ShakeAlert Is Not Earthquake Prediction. Cartoon showing that the earthquake has already started when the ShakeAlert message is distributed. ShakeAlert®-Powered Alert Delivery Levels
If an earthquake becomes large enough to meet USGS alert thresholds, a ShakeAlert Message is issued. ShakeAlert technical partners use this information to produce and deliver alerts that rapidly prompts people to take a protective action, such as DROP, COVER, AND HOLD ON, and/or to trigger an automated action that can protect vital systems, equipment, facilities, and infrastructure. These automated actions could include slowing a train, closing valves, issuing a public announcement, and many others.
Alert Delivery Thresholds used by ShakeAlert partners - The USGS issues ShakeAlert Messages but delivery of alerts will come by other public and private means (internet, radio, television, cellular), including Wireless Emergency Alerts (WEA) delivered by FEMA’s Integrated Public Alert and Warning System (IPAWS). For example, cell phone app providers and Android can deliver ShakeAlert-powered alerts to people who could feel weak shaking (Modified Mercalli Intensity - MMI III) or greater for earthquakes M4.5 and larger. For people who could feel moderate shaking (MMI V) or greater Android delivers alerts with more urgent language.
The Modified Mercalli Intensity (MMI) Scale is composed of increasing levels of intensity that range from imperceptible shaking to catastrophic destruction; levels of intensity are designated by Roman numerals. The MMI Scale does not have a mathematical basis; instead, it is a holistic ranking based on observed effects. The lower range of the MMI scale generally deals with the manner in which the earthquake is felt by people. The higher range considers observed structural damage.
Earthquake Intensity Scale (Abridged). The Modified Mercalli Intensity (MMI) Scale is composed of increasing levels of intensity that range from imperceptible shaking to catastrophic destruction; levels of intensity are designated by Roman numerals. The MMI Scale does not have a mathematical basis; instead, it is a holistic ranking based on observed effects. The lower range of the MMI scale generally deals with the manner in which the earthquake is felt by people. The higher range considers observed structural damage. For More Information:
- Publications
Filter Total Items: 32
Earthquake early warning for estimating floor shaking levels of tall buildings
This article investigates methods to improve earthquake early warning (EEW) predictions of shaking levels for residents of tall buildings. In the current U.S. Geological Survey ShakeAlert EEW system, regions far from an epicenter will not receive alerts due to low predicted ground‐shaking intensities. However, residents of tall buildings in those areas may still experience significant shaking dueAuthorsS. Farid Ghahari, Annemarie S. Baltay, Mehmet Çelebi, Grace Alexandra Parker, Jeffrey McGuire, Ertugrul TacirogluThe impact of 3D finite‐fault information on ground‐motion forecasting for earthquake early warning
We identify aspects of finite‐source parameterization that strongly affect the accuracy of estimated ground motion for earthquake early warning (EEW). EEW systems aim to alert users to impending shaking before it reaches them. The U.S. West Coast EEW system, ShakeAlert, currently uses two algorithms based on seismic data to characterize the earthquake’s location, magnitude, and origin time, treatiAuthorsJessica R. Murray, Eric M. Thompson, Annemarie S. Baltay, Sarah E. MinsonEvidence-based guidelines for protective actions and earthquake early warning systems
Earthquake early warning systems (EEW) are becoming increasingly available or in development throughout the world. With public alerting in Mexico, Japan, Taiwan, and parts of the United States, it is important to provide evidence-based recommendations for protective action so people can protect themselves when they receive an alert. Best-practice warning communication research suggests that providAuthorsSara K. McBride, Hollie Smith, Meredith Morgoch, Danielle Sumy, Mariah Jenkins, Lori Peek, Ann Bostrom, Dare Baldwin, Beth Reddy, Robert M. de Groot, Julia Becker, David Johnston, Michelle WoodExpected warning times from the ShakeAlert earthquake early warning system for earthquakes in the Pacific Northwest
The ShakeAlert® earthquake early warning system has been live since October 2019 for the testing of public alerting to mobile devices in California and will soon begin testing this modality in Oregon and Washington. The Pacific Northwest presents new challenges and opportunities for ShakeAlert owing to the different types of earthquakes that occur in the Cascadia subduction zone. Many locations inAuthorsJeffrey J. McGuire, Deborah E. Smith, Arthur D. Frankel, Erin A. Wirth, Sara K. McBride, Robert M. de GrootCommentary: The role of geodetic algorithms for earthquake early warning in Cascadia
The ShakeAlert earthquake early warning (EEW) system issues public alerts in California and will soon extend to Oregon and Washington. The Cascadia subduction zone presents significant new challenges and opportunities for EEW. Initial publications suggested that EEW algorithms based on Global Navigation Satellite System (GNSS) data could provide improved warning for intraslab events and dramaticalAuthorsJeffrey McGuire, Sarah E. Minson, Jessica R. Murray, Benjamin A. BrooksEarthquake early warning in Aotearoa New Zealand: A survey of public perspectives to guide warning system development
Earthquake early warning (EEW) can be used to detect earthquakes and provide advanced notification of strong shaking, allowing pre-emptive actions to be taken that not only benefit infrastructure but reduce injuries and fatalities. Currently Aotearoa New Zealand does not have a nationwide EEW system, so a survey of the public was undertaken to understand whether EEW was considered useful and accepAuthorsJulia S. Becker, Sally H. Potter, Lauren Vinnel, Kazuya Nakayachi, Sara McBride, David A. JohnstonDeveloping post-alert messaging for ShakeAlert, the earthquake early warning system for the West Coast of the United States of America
As ShakeAlert, the earthquake early warning system for the West Coast of the U.S., begins its transition to operational public alerting, we explore how post-alert messaging might represent system performance. Planned post-alert messaging can provide timely, crucial information to both emergency managers and ShakeAlert operators as well as calibrate expectations among various publics or public userAuthorsSara McBride, Ann Bostrom, Jeannette Sutton, Robert Michael deGroot, Annemarie S. Baltay, Brian Terbush, Paul Bodin, Maximilian Dixon, Emily Holland, Ryan Arba, Paul C. Laustsen, Sophia Liu, Margaret VinciShakeAlert Earthquake Early Warning System Performance During the 2019 Ridgecrest Earthquake Sequence
During July 2019, a sequence of earthquakes including a Mw6.4 foreshock and a Mw7.1 mainshock occurred near Ridgecrest, California. ShakeAlert, the U.S. Geological Survey (USGS) ShakeAlert public Earthquake Early Warning (EEW) system being developed for the U.S. West Coast, was operational during this time, though public alerting was only available within LA County. ShakeAlert created alert messagAuthorsAngela Chung, Men-Andrin Meier, Jennifer Andrews, Maren Böse, Brendan Crowell, Jeffrey McGuire, Deborah SmithThe potential of using dynamic strains in earthquake early warning applications
We investigate the potential of using borehole strainmeter data from the Network of the Americas (NOTA) and the U.S. Geological Survey networks to estimate earthquake moment magnitudes for earthquake early warning (EEW) applications. We derive an empirical equation relating peak dynamic strain, earthquake moment magnitude, and hypocentral distance, and investigate the effects of different types ofAuthorsNoha Sameh Ahmed Farghal, Andrew J Barbour, John LangbeinPractical limitations of Earthquake Early Warning
Earthquake Early Earning (EEW) entails detection of initial earthquake shaking and rapid estimation and notification to users prior to imminent, stronger shaking. EEW is coming to the U.S. West Coast. But what are the technical and social challenges to delivering actionable information on earthquake shaking before it arrives? Although there will be tangible benefits, there are also limitations. BaAuthorsDavid J. WaldEarthquake early warning ShakeAlert 2.0: Public rollout
The ShakeAlert Earthquake Early Warning System is designed to automatically identify and characterize the initiation and rupture evolution of large earthquakes, estimate the intensity of ground shaking that will result, and deliver alerts to people and systems that may experience shaking, prior to the occurrence of shaking at their location. It is configured to issue alerts to locations within theAuthorsMonica Kohler, Deborah E. Smith, Jennifer Andrews, Angela I. Chung, Renate Hartog, Ivan Henson, Doug Given, Robert Michael deGroot, Stephen Robert GuiwitsEstimating rupture dimensions of three major earthquakes in Sichuan, China, for early warning and rapid loss estimates
Large earthquakes like in Wenchuan in 2008, MW 7.9, Sichuan, China, provide opportunity for earthquake early warning (EEW) as many heavily shaken areas are far (~50 km) from the epicenter and warning time could be long enough (≥ 5 s) to take effective preventative action. On the other hand, earthquakes with magnitudes larger than ~M 6.5 are challenging for EEW since source dimensions need to be deAuthorsJiawei Li, Maren Böse, Max Wyss, David J. Wald, Alexandra Hutchinson, John F. Clinton, Zhongliang Wu, Changsheng Jiang, Shiyong Zhou - News
Filter Total Items: 16
- FAQ
How do I sign up for the ShakeAlert® Earthquake Early Warning System?
How do I sign up to receive ShakeAlert®-powered Alerts on my phone? Provider Type Apple Store/Google Play Link States USGS/FEMA Wireless Emergency Alerts N/A FEMA | WEA CA/OR/WA MyShakeTM Mobile App Y/Y MyShake CA/OR/WA QuakeAlertUSA Mobile App Y/Y QuakeAlertUSA CA/OR Google Android Operating System N/A Google CA/OR/WA San Diego Emergency (SD Emergency) with ShakeReadySD Mobile App Y/Y Ready San...
Can I get on a list to receive an email message when there is an earthquake? How do I sign up for earthquake notifications? Are there any Feeds I can subscribe to?
Please go to the USGS Earthquake Notification Services (ENS) to sign up for free emails or text messages to your phone. Use the default settings or customize ENS to fit your needs. Also check out the many different Earthquake Feeds. ENS is NOT an earthquake early warning system. Messages issued by ENS will almost always arrive after you would feel any shaking. Learn more: How do I sign up for...
- Partners
Filter Total Items: 17