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USGS ShakeAlert Profile picture
@USGS_ShakeAlert
Oct 9, 2019 • 12 tweets • 8 min read • Read on X
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#ShakeAlert focuses on eq shaking which is controlled by 3 main factors: magnitude, distance from the rupturing fault, and local ground conditions. These factors play a role in how hard and for how long a region will shake. @IRIS_EPO video explains #USGSRemembers #LomaPrieta
@IRIS_EPO Generally, the closer to an earthquake the stronger the shaking you will feel. The Cypress St. viaduct along the Nimitz Freeway (I-880) was 55 miles away from the #LomaPrieta EQ. Why did the viaduct experience such heavy shaking, which caused its tragic collapse? (1/2) Image
During an earthquake, loose, soft soil will shake harder and longer than hard rock. Valleys will shake harder than mountains because of their sediment fill. Watch this video from @IRIS_EPO: iris.edu/hq/inclass/ani…
#USGSRemembers (2/2)
@IRIS_EPO Getting out rapid information about an earthquake that has already begun is critical. A #ShakeAlert is a data package USGS makes available to 60+ partners so they can deliver alerts to people and/or trigger automated actions such as slow a train or protect a water supply. Image
A #ShakeAlert is one of the many earthquake information products offered by the USGS Advanced National Seismic System (ANSS). Other products include ShakeMap, National Hazard Maps, and Did You Feel It? Learn more about ANSS at: earthquake.usgs.gov/monitoring/ans…
Compared to other ANSS products, #ShakeAlert is first out of the gate. All of the products serve important roles in contributing critical information about earthquakes and their effects. Learn more about ANSS products at: earthquake.usgs.gov/monitoring/ans… Image
All components of the #ShakeAlert System must work quickly to get alerts to their destination. The USGS ANSS component in dark blue (ground motion detection by seismometers to issuing the ShakeAlert) are the first steps in the process. Image
Once ground motion is detected by seismic stations, information is sent in a fraction of a second to a #ShakeAlert processing center. There are 3 centers, 1 in Washington and 2 in California. ShakeAlert software makes very quick decisions from an early snapshot of the earthquake.
#ShakeAlert software is very sophisticated and works very fast. Pretend you are a ShakeAlert processing center. Is this snapshot of ground motion data an earthquake? (Answer will follow) Image
If you said yes - you've issued a successful ShakeAlert! Good job! This record is from the M6.0 South Napa earthquake on 8/24/14. Learn more about this earthquake at: earthquake.usgs.gov/earthquakes/ev… Image
In seconds, the #ShakeAlert system produces a package that has information about the location, initial magnitude, and estimated shaking intensity across the affected region. This information will help ShakeAlert partners make decisions about alert delivery. Image
The ShakeAlert system continues to refine these ground motion estimates and updates ShakeAlerts as the earthquake grows and more sensor data become available.

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More from @USGS_ShakeAlert

USGS ShakeAlert Profile picture
Oct 19, 2021
Why “Drop, Cover, and Hold On” when you get a #ShakeAlert-powered alert📱? How do we know this is the best action to take? Check out this social science research! library.seg.org/doi/10.1190/ge…. Let’s dive in 🧵. @Cal_OES @ShakeOut @waEMD @OregonOEM @CAGeoSurvey @RocketRules1 @ECA
For a successful #EEW system to reduce injuries, 3 things should be considered: 1) the people who are alerted and the building types they occupy, 2) demographic variables such as gender, age, as well as quake experience & 3) types of quakes and performance of the EEW system. Image
The #ShakeAlert team analyzed earthquake injuries and deaths, focusing on quakes from the 1970s to now. Several studies from CA (Loma Prieta & Northridge) and WA (Nisqually) showed that people who move during shaking are twice as likely to be injured than those who don’t. @fema Image
Read 9 tweets
USGS ShakeAlert Profile picture
Oct 1, 2020
A shaky afternoon in Southern California. Hope everyone is safe. Did you feel the M4.9 #earthquake near Westmorland at 5:31 pm PT? The #ShakeAlert system issued a message and passed it along to our delivery partners. If you received a message, share a screenshot with us!
.#ShakeAlert powered #earthquake alerts were delivered by the @MyShakeApp and @fema Wireless Emergency Alert System - WEA. You can find this map at: prod-earthquake.cr.usgs.gov/earthquakes/ev… Check out the map - if you are inside the MMI 3 (weak) polygon you might have received an alert.
If you are inside the MMI 4 (light shaking) polygon you might have gotten more than one alert. That's good since we want you to get alerts through every pathway possible. The WEA the message reads: "Earthquake Detected! Drop, Cover, Hold On. Protect Yourself. -USGS ShakeAlert"
Read 5 tweets
USGS ShakeAlert Profile picture
Sep 25, 2020
Did you know that it is National Postdoc Appreciation Week #NPAW? For #ResearchFriday, we are focusing on the great work of our early career researchers! Currently we have four @USGS postdocs working to improve the #ShakeAlert system. Let the shout-outs begin! @USGS_Quakes Image
Dr. Noha Farghal has a Ph.D. in geophysics from @Stanford. Noha is working on incorporating fiber-optic sensors into the #ShakeAlert system. Check out her recent paper: The Potential of Using Dynamic Strains in Earthquake Early Warning Applications pubs.geoscienceworld.org/ssa/srl/articl… Image
.@UCLA Bruin Dr. Grace Parker studies ground shaking and works on models to better estimate ground motion in SoCal for #ShakeAlert & best practices for using @PEER_Center NGA-Subduction ground motion models for Cascadia in EEW algorithms.@UCLACivil @Garrickinstitut #PDAW2020 Image
Read 6 tweets
USGS ShakeAlert Profile picture
Sep 19, 2020
A shaky Friday evening in Southern California. Hope everyone is safe. Did you feel the M4.6 #earthquake about 2 miles west of El Monte just before 11:39 pm PT? The #ShakeAlert system issued a message and passed it along to our delivery partners. More info: earthquake.usgs.gov/earthquakes/ev… Image
Let us know if you got an alert and share screen shots if you want. At this magnitude apps that are Powered by #ShakeAlert can deliver alerts to people who could feel MMI III (weak shaking) or greater. Check out how big the MMI III+ region is on this map. @Cal_OES Image
Check out the #ShakeAlert post-alert summary at: earthquake.usgs.gov/earthquakes/ev…. The first ShakeAlert Message was issued by @USGS 4.5s after the quake started. The quake was about 11 miles deep and it took about 3s for the first waves to reach the surface where they could be detected. Image
Read 6 tweets
USGS ShakeAlert Profile picture
Sep 18, 2020
Hi everyone, it’s #ResearchFriday! On top of having 60+ physical scientists on #ShakeAlert we have a team of 30+ social scientists who study human interaction with ShakeAlert. Meet the Social Science Working Group (SSWG). Here’s our class picture from 2020! Image
Why is social science important? Apart from sensors in the field, data processing centers, and alert delivery by our partners, people directly interact with #ShakeAlert. Anything that can improve that interaction, which often happens quickly, is critical to keeping people safe. Image
So what does the SSWG do? They work on research projects that are critical to improving #ShakeAlert…for you. That means everything from messaging to graphics to what channels to use to how groups use ShakeAlert is studied by SSWG. Image
Read 5 tweets
USGS ShakeAlert Profile picture
Sep 4, 2020
Happy #ResearchFriday! How does #ShakeAlert work and how do our 60+ partners use it to keep people safe? Here's the latest creation from @IRIS_EPO and the ShakeAlert Education & Outreach team - a new video to explain a pretty complex system. Please share! Image
Even #ShakeAlert animations are based on research. What went into making this new resource? Every detail counts and geologist Jenda Johnson spent hours getting everything just right. Just to animate Drop, Cover, and Hold On took 100+ individual frames! @ECA @waShakeOut @ShakeOut
Then there’s the work of pulling a team together to develop the story, get the facts right, and manage the review process. #ShakeAlert team member and seismologist Dr. Danielle Sumy led a team of over 10 people who weighed in on all aspects of this project.
Read 4 tweets

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