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Aug 7, 2020 10 tweets 4 min read Read on X
Hi everyone, it’s #ReseachFriday! This week’s focus is on #ShakeAlert alerting regions! This study looked at using the 2019 Ridgecrest earthquakes to find an optimal alerting strategy. pubs.geoscienceworld.org/ssa/bssa/artic…
So, the #ShakeAlert system detects an earthquake, it uses ground motion models (GMMs) to determine the size of the alert region using earthquake source estimates as input (generally, magnitude and location). Image
The authors first found which GMM predicts shaking intensities that match the average observed intensity with distance from USGS Did You Feel It? (DYFI?) reports on the Ridgecrest earthquakes. Here's the DYFI map from the M7.1 Ridgecrest earthquake. Image
DYFI? Reports are those reports that people fill out on the USGS website after they feel an earthquake. More here about those reports: earthquake.usgs.gov/data/dyfi/
Using the average-expected intensities in the alert region process is great, but ground motions vary for all sorts of reasons and there will be people who experience larger-than-expected shaking. The authors wanted to find a way to include these locations inside the alert region.
They did this by incorporating GMM uncertainties in the alert region calculation. In weather forecasts, if you’re told that you might experience 0-2 inches of rain, you’re going to bring your umbrella with you just in case! The authors took a similar approach here.
By picking the size of the alert region based on the maximum possible shaking at that location instead of just the average, the alert region can be expanded to include the locations that experience larger-than-expected shaking. Image
This can reduce the number of missed alerts, when people should have received an alert but didn’t. By incorporating uncertainty we can get 94% of the population who needed alerts for the Ridgecrest EQs inside the alert regions (assuming magnitude is estimated correctly).
And this is one way we are working to improve the #ShakeAlert system. Great work Dr. Jessie Saunders who is a USGS Mendenhall Postdoc. Paper is available at: pubs.geoscienceworld.org/ssa/bssa/artic… @IRIS_EPO
And oh yes - we know it should be #ResearchFriday. Happy Friday everyone!😀

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More from @USGS_ShakeAlert

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
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
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
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
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
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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