Brian Olson
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brianolson.bsky.social
Brian Olson
@brianolson.bsky.social
440 followers 300 following 140 posts
California geologist, earthquake hazards scientist, Christian, and frustrated Angels/Ducks/Browns fan. Peace & Humpty-ness Forever!

“Older than some people, but younger than some buildings.”
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brianolson.bsky.social
Tom Rockwell (Distinguished Lecture) kicking off the 2025 SCEC meeting! Small offset per event (smaller magnitude) produces narrower damage zone in nearby rocks. Serves as a proxy for max magnitude per rupture event. #scecmeet #scec2025 🧪
Tom Rockwell standing on the stage in front of 4 chairs. On the left is a large projection screen showing one of his slides that includes a photomicrograph of fractured mineral grains. A slide from Tom’s talk showing an annotated aerial view of the San Andreas Fault near Little Rock and a photomicrograph on the right showing pulverized mineral grains from a sample collected several meters from the main fault plane. Summary slide of Tom’s talk labeled: General Summary of Physical Damage. Includes three categories: small displacement (less than 1 meter), moderate (1.5 to 2.7 meter), and large displacement (3 to 6 meters).
September 8, 2025 at 1:38 AM
brianolson.bsky.social
Opening presentation of this year’s SCEC annual meeting in Palm Springs! It seems SCEC is a “large Enterprise” working to develop & share cutting-edge earthquake system science to enhance California’s resilience & to educate and inspire future scientists. #scecmeet #SCEC2025 🧪
Digital image off the USS Enterprise from the Star Trek franchise. Small pictures of the science researchers are in little circles around the edge. The bottom of the slide says: “To boldly go where no SCEC has gone before.”
September 8, 2025 at 12:48 AM
brianolson.bsky.social
It’s me! I’m “one scientist”! 🧪
Screen shot of an online article from the Los Angeles Times about this week’s magnitude 5.2 earthquake and the early warning notifications. The text says, “Geologists at the California Geological Survey’s office in Los Angeles also received early warning notifications on their phones ‘so we were prepared for some shaking,’ one scientist posted on social media.”
April 17, 2025 at 12:56 AM
brianolson.bsky.social
Us geologists here at the @cageosurvey.bsky.social LA office all got our early warning notifications on our phones so we were prepared for some shaking. Did you get one too?

Download @myshakeapp.bsky.social to be ready next time. #earthquake
Screenshot of MyShake notifications for a magnitude 5.8 earthquake (later revised to 5.2) in San Diego County. The alert reads: “Earthquake - Drop, cover, hold on. Mag 5.8 EQ in San Diego Country Estates, CA 92065, USA on 4-14-2025 at 10:08am PDT”. A second alert under the first says: “Earthquake Alert Earthquake Detected! Drop, Cover, Hold On. Protect yourself. - USGSShakeAlert.”
April 14, 2025 at 5:37 PM
brianolson.bsky.social
Felt the long-period shaking here in downtown LA from the M5.2 earthquake near Julian, CA (San Diego County). Epicenter is near the Elsinore Fault, which would be the primary suspect, but we'll see once more data comes in. #earthquake #Julian 🧪 @cageosurvey.bsky.social
This ShakeMap shows the ground shaking intensity from a magnitude 5.2 earthquake that occurred on April 14, 2025. The epicenter is marked with a black star and located just south of Julian, California, in San Diego County. The shaking intensity is represented using the Modified Mercalli Intensity (MMI) scale, with colors ranging from green (light shaking) near the epicenter to blue (weak shaking) farther out. The strongest shaking (MMI V to VI) was felt in the mountains and foothill regions northeast of San Diego, including areas near Mira Mesa and Encinitas. Seismic instrument locations are shown as triangles, and community-reported intensities are marked with small circles. Cities across Southern California and northern Baja California, including San Diego, Oceanside, Riverside, and Tijuana, experienced weak to light shaking. The scale at the bottom links MMI levels to estimated damage and ground motion levels, helping to interpret the impact across the region.
April 14, 2025 at 5:26 PM
brianolson.bsky.social
So encouraged by everyone we saw at the Hands Off rally yesterday in Santa Ana (Orange County)! #HandsOff

Rise Up. Wise Up. Eyes Up.
A crowd of protesters at a rally. One of them is holding up a black sign with an outline of the United States with the words “Rise Up!” written inside. A group of protestors on the sidewalk. One is holding a cardboard sign that reads “It’s so bad, introverts are here! Hands off our Constitution.” A woman sitting on the curb with a white sign that reads “Thisis just not OK!”
April 6, 2025 at 6:26 PM
brianolson.bsky.social
Heading out to our local Orange County Hands Off rally shortly. #handsoff
Two t-shirts, a blue one reading “ano more Kings” with a cartoon drawing of King George III sitting on a stool with bags of money from Schoolhouse Rock. The second is a white shirt with multicolored balloons on top the word “No”.
April 5, 2025 at 7:34 PM
brianolson.bsky.social
Talks went very well and a great time was had by all!
Photo of Wendy Bohon giving a presentation at the Geological Society of America, Cordilleran Section meeting in Sacramento. She is in a hotel conference room standing behind a wooden lectern with her arm lifted and extended towards the projection screen. On the screen is a map of California showing the largest potential earthquake shaking intensities for each area of the state. Photo of Brian Olson giving a presentation at the Geological Society of America, Cordilleran Section meeting in Sacramento. He is in a hotel conference room standing behind a wooden lectern addressing the audience. A sign at the top front of the lectern reads “Holiday Inn Sacramento” and another sign at the bottom reads “The Geological Society of America”. Title slide of Brian Olson’s presentation that reads “Liquefaction Hazard Zone Mapping in the Greater Sacramento Area, Sacramento and Yolo Counties, Northern California.” At the top left is a multi-colored version of the California gear from the state flag with text to the right that reads “California Department of Conservation, California Geological Survey”. In the lower left is Brian’s name, job title (Senior Engineering Geologist), and CGS’ social media handle of “@CAGeoSurvey”.
April 5, 2025 at 1:57 AM
brianolson.bsky.social
Anyone have any insight into why this M3.1 in the Sacramento delta is SO deep? 🧪
Map of the San Francisco Bay and Sacramento River delta and surrounding areas. A white circle is shown north of the city of Antioch representing the epicenter of a magnitude 3.1 earthquake. A white box with details about the quake is shown in the lower left corner. It states this earthquake was 13 kilometers west of Rio Vista, CA occurring at 8:37am on April 4. The hypocenter is listed at 24.6 kilometers and is highlighted in yellow for emphasis.
April 4, 2025 at 5:59 PM
brianolson.bsky.social
If you're at the GSA Cordilleran Section meeting in Sacramento tomorrow, stop by the "Earthquake Hazards in Applied Geology" session tomorrow morning and catch me and Wendy Bohon in action as we represent the California Geological Survey! 🧪 @drwendyrocks.bsky.social @cageosurvey.bsky.social
Screen shot of the Friday morning schedule of speakers with orange boxes highlighting a talk by Wendy Bohon entitled "Earthquake Science in Public Service: Working to Keep Earthquake Hazards from becoming Earthquake Disasters" at 8:00am and a talk by Brian Olson entitled " Liquefaction Hazard Zone Mapping in the Greater Sacramento Area, Sacramento and Yolo Counties, northern California" at 9:10am.
April 4, 2025 at 4:45 AM
brianolson.bsky.social
Example from La Cañada showing progressive residential development on an alluvial fan that has seen numerous debris flow flooding. Risk is changing with a warming climate, hazard is increasing with expanding construction. 🧪 #CDGSA2025 @cageosurvey.bsky.social
PowerPoint slide showing different topographic maps of one area of La Cañada showing more homes being built over time from 1928 to 2009. In 1928 the area is very lightly populated with scattered homes and by 2009 every lot is filled with homes and other buildings.
April 2, 2025 at 6:55 PM
brianolson.bsky.social
Jeremy Lancaster (California State Geologist) giving the lunchtime lecture at GSA on post-wildfire flooding & debris flow hazards. Highly developed alluvial fans are most prone. Studies find a minimum flow depth of 5 feet equaled total destruction of structures. @cageosurvey.bsky.social
California state geologist Jeremy Lancaster stands behind a podium speaking into the microphone giving a presentation. Title slide of Jeremy Lancaster’s talk reading “Post-Fire geohazard management in California’s warming climate”.
April 2, 2025 at 6:35 PM
brianolson.bsky.social
The USGS posted their aftershock forecast and they are saying there's a 40% chance of another M6+ earthquake in the next week. Certainly, there will be dozens to hundreds of smaller M4s and M5s. If you are in Bangkok, I doubt you'll feel quakes less than M6 though. Scary no matter what though.
USGS "Aftershock Forecast" graph for the recent magnitude 7.7 earthquake near Mandalay in Myanmar (Burma). According to the graph, in the next week, there is a 6 percent chance of another M7+ earthquake, 40% chance of a magnitude 6+ quake, and 97 percent chance of a magnitdue 5+ quake.
March 29, 2025 at 12:05 AM
brianolson.bsky.social
That's one way to start your weekend! A M4.6 earthquake shook the Bombay Beach/Salton Sea area this morning, just before 10:30am local time. This part of California has been rumbling with small M1-2 quakes since March 1. This could be the main shock of that sequence. #earthquake 🧪
Map of southern California and part of western Arizona showing geographic features, city names, major freeways, and dark gray lines representing known surface faults. Two orange circles represent recent earthquake epicenter locations. The northerly one is the magntiude 4.6 earthquake from this morning. It plots within the southern end of the Salton Sea in Imperial County.
March 14, 2025 at 6:59 PM
brianolson.bsky.social
Post-workshop brainstorming session. 😉
Stainless steel beer tanks inside a warehouse at Rogue Brewing.
March 8, 2025 at 2:48 AM
brianolson.bsky.social
Excellent 1-day workshop in Newport, OR discussing ground failures from past Cascadia earthquakes and planning for future ones.
Vertical banner in an interior hallway. It reads: “CRESCENT Cascadia Region Earthquake Science Center, Innovative Science for a Resilient Society” Exterior view of a vertical tsunami evacuation structure at the Hatfield Marine Science Center. A metal sign on a wooden post reads “Tsunami Evacuation Route” and points towards a concrete ramp that leads to the top of a 3-story building. View of a marina with scattered boats and a steel arch bridge in the distance at sunset. Elevator button panel with a button labeled “Seismic” and one with a “Tsunami Evacuation Route” sticker next to it.
March 8, 2025 at 2:42 AM
brianolson.bsky.social
Also, not the first cane raised in Congress, but this is to defend the honor of the poor and vulnerable, not wealthy elite slaveholders.
Political cartoon depicting the 1856 beating of Massachusetts Senator Charles Sumner by South Carolina Representative Preston Brooks at his desk days after giving a lengthy, excoriating speech against slavery and Congressional slaveholders. Sumner was beaten bloody and unconscious.
March 5, 2025 at 7:07 AM
brianolson.bsky.social
Quite the shimmy-shaking going on in central California, east of Salinas. This location is near where the San Andreas Fault transitions from the "locked" northern section to the middle "creeping" section. 19 earthquakes since 9pm-ish last night w/ a M3.9 being the largest. #earthquake 🧪
Map of central California, showing major cities including Salinas, San Jose, and Fresno. Dark gray lines represent know surface faults capable of generating earthquakes. Red circels represent epicenters of earthquakes that occurred within the last hour, orange circles are epicenters of quakes that happened within the last 24 hours.
February 22, 2025 at 5:58 PM
brianolson.bsky.social
LOVE “The Californians” ad for VW!! Although, unless they are coming San Diego/southern Orange County or Santa Clarita, they’re not taking the 5 to the 405 to the 10 to get to Malibu.
February 17, 2025 at 10:22 PM
brianolson.bsky.social
Here we go again!! A M3.7 earthquake just now near/on the Hayward Fault. Simmer down now! #earthquake 🧪
Shaded relief map of the San Francisco Bay Area and regions with dark gray lines representing mapped surface faults. A large red circle depict the most recent epicenter of today's earthquake sequence and they all plot very close to the mapped trace of the Hayward Fault. A table on the left lists magnitude 3.7, 3.2, 3.3, and 2.7 quakes have occurred in this area since 5:00am this morning local time.
February 13, 2025 at 10:08 PM
brianolson.bsky.social
Based on numerous paleoseismic studies along the Hayward Fault, we know large, ground-rupturing earthquakes happen about every 150 years. The last major event was a ~M6.8 quake in Oct. 1868, which was... [checks notes]... over 156 years ago. This is why we need to be alert & prepared. 🧪 #earthquake
Annotated timeline of major earthquakes on the Hayward Fault marked by yellow stars for the approximate year of the quake on the timeline. The labeled years are 1134, 1317, 1475, 1629, 1725, and 1868. Corresponding intervals between earthquakes are listed above the timeline and the intervals between major earthquakes are colored bars that range from 97 to 183 years in between major earthquakes. Major world hisotry events are noted by black arrows on the bottom of the timeline. These include signing the Magna Carta, Black Plague in Europe, Columbus reaches the New World, California missions founded, and the 1906 San Francisco Earthquake. This figure was created by the US Geological Survey.
February 13, 2025 at 9:15 PM
brianolson.bsky.social
Earlier this week, the San Andreas Fault popped off a few M3 quakes. Today the Hayward Fault is trying to get some attention with M3.2 and M3.4 earthquakes. Can we just NOT? #earthquake 🧪
Shaded relief map of the San Francisco Bay Area and regions with dark gray lines representing mapped surface faults. Two closely spaced red circles depict the epicenters of today's earthquakes and they plot very close to the mapped trace of the Hayward Fault. A table on the left lists magnitude 3.2, magnitude 3.4, and magnitude 2.7 quakes have occurred in this area since 5:00am this morning local time.
February 13, 2025 at 8:37 PM
brianolson.bsky.social
Couple minor quakes (M3.5 and M3.0) just now near/on the San Andreas Fault, north of San Bernardino, CA. Let's all be cool and not get too rumbly, m'kay? 🧪 #earthquake
Shaded relief map of southern California showing active surface faults with dark gray lines, freeways with thick pale red lines, and labeled cities. A red circle near the city of Highland marks the epicenter of the magnitude 3.5 earthquake. Text summary of the Caltech/USGS Southern California Seismic Network algorithm for the magnitude 3.5 earthquake. The analysis gives a 43 percent chance this earthquake was on the San Andreas Fault. Alternatively, the summary states there is a 55 percent chance it was on another fault in the Community Fault Model (CFM) and a 2 percent chance it was on a fault not in the CFM.
February 10, 2025 at 6:12 PM
brianolson.bsky.social
The USGS estimates strongest felt shaking only reached the “Light shaking” level. This is because the epicenter was so far offshore. It’s the same reason the initial magnitude was off. Hardly any offshore seismic stations, only land-based ones farther away. #earthquake 🧪
Table of “felt shaking” estimates from the magnitude 7.6 earthquake in the Caribbean Sea. Categories span “Not Felt” to “Extreme”. Highest felt shaking from this event was “Light”.
February 9, 2025 at 12:24 AM
brianolson.bsky.social
This earthquake is very likely on the primary transform plate boundary (Motagua Fault), which slides side-to-side and isn’t the kind of fault that forms large tsunamis. Because of its location, i expect most who feel it will only feel weak shaking. #earthquake 🧪
Tectonic map of the Caribbean Sea and islands. Map shows major plate boundaries (dotted lines) and major cities and countries labeled. Today’s earthquake was on the westernmost portion of the northern boundary fault.
February 9, 2025 at 12:06 AM