USGS ShakeAlert

We know that feeling the ground shake can be unsettling and many of you in Southern California have received several ShakeAlert EEW alerts tonight. The USGS earthquakes team is here with you 24/7 🏪 getting information out so you can stay safe. We’re in this together 🤝. Be safe everyone! Learn how to Be ShakeAlert Ready: usgs.gov/FAQ/BeShakeAle… @ImperialCntyCA @SanDiegoCounty @RivCoNow @Cal_OES @CAseismic @FEMARegion9 @CaltransHQ @USGS_Quakes @USGS 📷Image with recommended protective actions from the USGS and all ShakeAlert partners in California, Oregon, and Washington.

Thanks for the clarification Mamoru. Providing this data (and in this format) to the public is a relatively new thing and follow up is needed - we can always improve. However, prior to the debut of this resource, USGS social scientists, conducted usability testing to release a product that would have a better chance to be broadly accessible. The talking points below the section “Be Ready for More Earthquakes” were designed by our team to explain the main takeaways from all forecasts. We realize that the data will always need some interpretation depending on the audience. Our team is especially interested in making products like this more accessible and usable by emergency managers in operational settings so they can advance public safety. We’ve included Aftershock Forecasting in this new project: shakealert.org/wp-content/upl…

@USGS_ShakeAlert Hi　My intention was "how is this information perceived in society". I want to know if society understands and is using this information.

アメリカ地質調査所は余震の発生について確率的な予測を出しているのですがこれはどのように受け止められているのでしょうか

Did you know there are at least three (3) ways to get ShakeAlert-powered Earthquake Early Warning on your phone? 😎 All three ways are based on advanced technology and capable of providing an alert in advance of strong shaking from an earthquake. Learn how to be ShakeAlert Ready here: usgs.gov/FAQ/BeShakeAle… 📷Graphic on how to get ShakeAlert-powered EEW on your phone.

Earthquake Early Warning alerts were sent by the MyShakeApp ahead of this morning’s M4.7 earthquake near Brawley in Imperial County. The earthquake swarm occurring in Imperial County is a great reminder to be prepared. Download the MyShake app to get an alert crucial seconds before shaking starts!

@KarstenScott86 @Cal_OES Thanks for your question Karsten: You can get ShakeAlert-powered EEW alerts from MyShake and others here: usgs.gov/FAQ/BeShakeAle… 📷Graphic on how to get ShakeAlert-powered EEW on your phone.

@juanita59 Juanita - one more quick note about aftershocks: Aftershocks become less frequent with time, although they can continue for days, weeks, months, or even years for a very large mainshock.

Hi Juanita - thank you for your question. Earthquake scientists (like all of us) look for patterns. Part of understanding how earthquakes work is to look for patterns of when and where they happen and how big they are. Earthquake swarms don't have a big earthquake (also called a mainshock) that kicks off a sequence of quakes which are called aftershocks. Swarms don't follow the patterns that are observed in aftershocks. Swarms can last for hours, days, or months! Swarms often happen at the same locations. Most swarms are associated with geothermal activity. An example of a recent swarm is in Northern California is in the San Ramon Valley which is east of Oakland. This area has had several swarms since the year 2000. Here is a link to more information about earthquake swarms: usgs.gov/faqs/what-diff…

Learn more about the temporary increase in earthquake activity near Brawley, CA - known as a seismic swarm. The USGS assesses that the earthquake caused no-to-light damage from shaking. Approximately 180 thousand people experienced Light (MMI IV) to Strong (MMI VI) shaking. The ShakeAlert Earthquake Early Warning System was activated several times resulting in alert deliveries to cell phones. 👉If you feel shaking or get an alert: Drop, Cover, and Hold On. Stay safe everyone. Learn more about the Brawley swarm here: earthquake.usgs.gov/earthquakes/ma… @USGS_Quakes @Cal_OES @CaltechSeismo @CAGeoSurvey @FEMARegion9 @CAStateParks @ImperialCntyCA @UOHazardsLab @USGS @SanDiegoCounty 📸Screenshot of the Brawley seismic swarm with currently 344 events in the sequence (as of 8:45 am Pacific Time on 5/10). The southern end of the Salton Sea is shown upper left.

We know that feeling the ground shake can be unsettling and many of you in Southern California have received several ShakeAlert EEW alerts. The USGS earthquakes team and Cal OES are here with you 24/7 getting information out so you can stay safe. We’re in this together. Be safe everyone! Learn how to Be ShakeAlert Ready: usgs.gov/FAQ/BeShakeAle… @ImperialCntyCA @SanDiegoCounty @RivCoNow @Cal_OES @CAseismic @FEMARegion9 @CaltransHQ @USGS_Quakes @USGS 📷Image with recommended protective actions from the USGS and all ShakeAlert partners in California, Oregon, and Washington.

Cal OES is actively coordinating with local partners, as Imperial County experiences an earthquake swarm - the strongest a M4.7 near Brawley. Cal OES continues to assess developments to help keep Californians safe.

@TriciaW4lker @USGS_Quakes @Cal_OES @CAGeoSurvey @ImperialCntyCA Thanks for your question Tricia. This is a temporary increase in activity known as a seismic swarm. You can learn more about the events involved here: earthquake.usgs.gov/earthquakes/ev…. Scroll down the page for the info about the swarm.

@USGS_ShakeAlert @USGS_Quakes @Cal_OES @CAGeoSurvey @ImperialCntyCA What's going on with Brawley ? 270 minor quakes in the last 24 hours.

Good morning Southern CA. The ShakeAlert Earthquake Early Warning system was activated for a magnitude 4.2 earthquake about 2 miles northwest of Brawley at 12:10 am. Learn more about this earthquake: earthquake.usgs.gov/earthquakes/ev… @USGS_Quakes @Cal_OES @CAGeoSurvey @ImperialCntyCA @FEMARegion9 @SanDiegoCounty 📷Image showing USGS ShakeMap for this earthquake.

@CaltechSeismo The link doesn't appear to work. Thank you Caltech!

A swarm sequence has been confirmed near #Brawley, CA, #SouthernCalifornia #Earthquake. This is a typical sequence for the area, with 81 events catalogued so far, including a M4.4 at 7:22 PDT. You can read more about it here: scsn.org/index.php/2026…

Update: The magnitude for this event has been revised to M4.7.

Since the ShakeAlert system estimated this quake at magnitude 4.5 or greater alerts were delivered to cell phones or other devices by our Alert Delivery Partners in California through cell phone operating systems and mobile apps. Did you receive an alert? Please share a screenshot if you like. Thanks! 🎥Animation showing how the ShakeAlert System works.

It has been a shaky night in Imperial County, CA. 🫨 Wonder what USGS thinks might happen next? USGS aftershock forecasts give us an understanding of the chances of having more earthquakes within a given time period in the affected area. Check out the aftershock forecast since the magnitude 4.5 earthquake at 8:39 pm: earthquake.usgs.gov/earthquakes/ev… Aftershocks can also activate the ShakeAlert system. If you feel shaking or get an alert: Drop, Cover, and Hold On. @Cal_OES @CAGeoSurvey @ImperialCntyCA @SanDiegoCounty @FEMARegion9 @USGS_Quakes @USGS 📷Image with information about USGS Aftershock Forecasts.

@USGS_Quakes Stay safe out there in earthquake country! Anyone can be ShakeAlert Ready. Learn more about how to set up your phone to get EEW alerts: usgs.gov/FAQ/BeShakeAle… 📷Image showing one of the most common ways that people receive ShakeAlert EEW alerts - through their cell phone.

How much data does ShakeAlert need to estimate a quake’s location, magnitude, & how hard it’s going to shake? Put your hand on your heart - the data collected in the time of a couple of heartbeats is enough. 🎥Using heartbeats, how long it takes the ShakeAlert EEW system to estimate a quake’s location, size, and shaking distribution.

Good evening Southern CA. The ShakeAlert Earthquake Early Warning system was activated for a magnitude 4.3 earthquake about 1 mile northwest of Brawley at 8:39 pm. Learn more about this earthquake: earthquake.usgs.gov/earthquakes/ev… @USGS_Quakes @Cal_OES @CAGeoSurvey @ImperialCntyCA @FEMARegion9 @SanDiegoCounty 📷Image showing USGS ShakeMap for this earthquake.