Hi Idaho,
So you just had a significant earthquake. That's not fun.
earthquake.usgs.gov/earthquakes/ev…
You might get aftershocks. Please remember to Drop! (or Lock!), Cover! & Hold on! until shaking finishes.
Please fill out a Did You Feel It? report:
earthquake.usgs.gov/earthquakes/ev…
So you just had a significant earthquake. That's not fun.
earthquake.usgs.gov/earthquakes/ev…
You might get aftershocks. Please remember to Drop! (or Lock!), Cover! & Hold on! until shaking finishes.
Please fill out a Did You Feel It? report:
earthquake.usgs.gov/earthquakes/ev…
Earthquakes in Idaho are part of that same Basin & Range geology we talked about with Utah.
It's NOT the same faults or seismic stress field (this is too far away to be an aftershock from Utah), but the same concept of sliding blocks under tension.
It's NOT the same faults or seismic stress field (this is too far away to be an aftershock from Utah), but the same concept of sliding blocks under tension.
Idaho can also get earthquakes related to the Yellowstone hot spot as magma shifts underground, so let's head this off right away:
Yellowstone is at activity level green. Everything is normal. It's not gearing up to kill us in the near future.
See? volcanoes.usgs.gov/observatories/…
Yellowstone is at activity level green. Everything is normal. It's not gearing up to kill us in the near future.
See? volcanoes.usgs.gov/observatories/…
Earthquakes have the same magnitude everywhere because that's how much energy is released when the fault overcome stress & breaks.
Currently this is reported as M6.5, but it's normal for that number to change as more data comes in & we get a breather to do full math & analysis.
Currently this is reported as M6.5, but it's normal for that number to change as more data comes in & we get a breather to do full math & analysis.
But! Earthquakes FEEL differently depending on context.
Intensity changes with distance (more nearby), surface geology (loose wet sediment wobbles more than rock), even building structure (wood sways more than concrete; short vs tall swaying frequency).
Intensity changes with distance (more nearby), surface geology (loose wet sediment wobbles more than rock), even building structure (wood sways more than concrete; short vs tall swaying frequency).
Seismometers give us detailed data for calculating magnitude, but intensity is so qualitative that we need your help.
We want those Did You Feel It? reports to understand how earthquakes are experienced in different circumstances so we can make better hazard maps & reduce risk.
We want those Did You Feel It? reports to understand how earthquakes are experienced in different circumstances so we can make better hazard maps & reduce risk.
We use these beachball-looking diagrams to indicate primary stress directions of earthquakes.
Idaho's earthquakes are usually on normal faults: tension pulling apart leads to a block slipping down.
Today looks more like strike-slip (side-to-side) motion.
Idaho's earthquakes are usually on normal faults: tension pulling apart leads to a block slipping down.
Today looks more like strike-slip (side-to-side) motion.
We don't typically think of Idaho as being unstable ground, but they definitely pop up on the national seismic hazard map.
Part of the problem is nearly all cities are built on sediments.
📷 USGS (usgs.gov/natural-hazard… & usgs.gov/media/images/2…)
Part of the problem is nearly all cities are built on sediments.
📷 USGS (usgs.gov/natural-hazard… & usgs.gov/media/images/2…)
I'm seeing aftershocks pop up: earthquake.usgs.gov/earthquakes/ev…
Aftershocks are scary because you don't know when the shaking will happen, so you're in high anxiety all the time.
Remember to Drop! (or Lock!), Cover!, and Hold on! Trying to outrun an earthquake will get you hurt.
Aftershocks are scary because you don't know when the shaking will happen, so you're in high anxiety all the time.
Remember to Drop! (or Lock!), Cover!, and Hold on! Trying to outrun an earthquake will get you hurt.
A fault moves, releasing stress, but impacts all the faults nearby. They sometimes shift in response.
I think of it like a pile of puppies . One fidgets, smacking the next. Most of the time, they slowly calm down, but sometimes someone smacks a nose & sets them off again.
I think of it like a pile of puppies . One fidgets, smacking the next. Most of the time, they slowly calm down, but sometimes someone smacks a nose & sets them off again.
Have geology questions about the #IdahoEarthquake? Ask!
Geoscience twitter is here to help soothe your nerves about uncertainty.
And if you need direct action? Here's universally applicable and doable RIGHT NOW disaster prep:
Geoscience twitter is here to help soothe your nerves about uncertainty.
And if you need direct action? Here's universally applicable and doable RIGHT NOW disaster prep:
We think of the coastal states as being up front & personal with faults (San Andreas in California; Cascadia in NorCal through BC)
But the entire west is under extensional stress. Basin & Range are a series of horst & grabens pulling apart under tension.
But the entire west is under extensional stress. Basin & Range are a series of horst & grabens pulling apart under tension.
Whoops, split my thread.
Gluing it back together for navigation:
Gluing it back together for navigation:
Aftershock forecast: earthquake.usgs.gov/earthquakes/ev…
tl;dr You're incredibly likely to get 4-790 M3 or smaller earthquakes that feel like a truck passing. You're less likely to get more M4+ but it's possible.
tl;dr You're incredibly likely to get 4-790 M3 or smaller earthquakes that feel like a truck passing. You're less likely to get more M4+ but it's possible.
Q: YELLOWSTONE IS GOING TO KILL US.
A: It's really not.
This earthquake is in the Central Idaho Seismic Zone. It has nothing in common with the Yellowstone seismic system.
And it's home to most of the bigger historical quakes: idahogeology.org/historical-ear…
A: It's really not.
This earthquake is in the Central Idaho Seismic Zone. It has nothing in common with the Yellowstone seismic system.
And it's home to most of the bigger historical quakes: idahogeology.org/historical-ear…
Ahhh so cool!!! Swimming pool seismic seiche caught on camera. Anyone else have footage?
Ever scoot back & forth in a bathtub, making a bigger & bigger wave? Same concept of constructive interference as earthquake shakes at pool's resonance frequency.
Ever scoot back & forth in a bathtub, making a bigger & bigger wave? Same concept of constructive interference as earthquake shakes at pool's resonance frequency.
Have you ever been at the beach and wiggled your toes to sink into wet sand?
That liquefaction process happens when earthquakes shake saturated sediments like river valleys. I'd expect at least some somewhere in Idaho.
NZ 2011:
That liquefaction process happens when earthquakes shake saturated sediments like river valleys. I'd expect at least some somewhere in Idaho.
NZ 2011:
Location is critically important with earthquakes.
A M6+ event is a significant quake that can cause death & damage if it happens directly under a city. But this quake was far enough away to be scary but (hopefully) not deadly.
earthquake.usgs.gov/earthquakes/ev… & earthquake.usgs.gov/earthquakes/ev…
A M6+ event is a significant quake that can cause death & damage if it happens directly under a city. But this quake was far enough away to be scary but (hopefully) not deadly.
earthquake.usgs.gov/earthquakes/ev… & earthquake.usgs.gov/earthquakes/ev…
This deeply amuses me.
Alas, Shake Creek is named for being the origin of cutting shake bolts (short logs that were destined to be split into basic wooden shingles) for Oxford Ranger Station.
Details: npshistory.com/publications/u…
Alas, Shake Creek is named for being the origin of cutting shake bolts (short logs that were destined to be split into basic wooden shingles) for Oxford Ranger Station.
Details: npshistory.com/publications/u…
Q: Are we getting more earthquakes? It seems like a lot.
A: Nope, you're just paying attention.
We detect ~500,000 earthquakes a year, of which 20,000 are big enough for people to notice. We have 1-2,000 M5+ quakes yearly, or a few every day!
Details: usgs.gov/natural-hazard…
A: Nope, you're just paying attention.
We detect ~500,000 earthquakes a year, of which 20,000 are big enough for people to notice. We have 1-2,000 M5+ quakes yearly, or a few every day!
Details: usgs.gov/natural-hazard…
Q: But all these quakes are so close together...?
A: Earthquake magnitude is roughly proportional to the amount of fault that moved (fault rupture length). They only influence roughly 2-3x that distance.
The Earth is big. Like, really big.
Idaho & Utah are like 500 miles apart!
A: Earthquake magnitude is roughly proportional to the amount of fault that moved (fault rupture length). They only influence roughly 2-3x that distance.
The Earth is big. Like, really big.
Idaho & Utah are like 500 miles apart!
Update: USGS identifies the event as southwest-northeast extension just north of the Snake River Plain in the Intermountain Seismic Belt & Centennial Tectonic Belt.
This changes none of the concepts or interpretation
📷 Smith et al 2004; @IdahoStateU (geology.isu.edu/Digital_Geolog…)
This changes none of the concepts or interpretation
📷 Smith et al 2004; @IdahoStateU (geology.isu.edu/Digital_Geolog…)
Ooooh, now on a regional fault map.
Look at all those faults having absolutely nothing to do with Yellowstone!
Look at all those faults having absolutely nothing to do with Yellowstone!
Seismologists try to get to the field ASAP after an earthquake to document any surface rupture or displacement (& add temporary seismometers to catch aftershocks.
That’s challenging Because Pandemic, but also snow & (quake-triggered??) avalanches.
That’s challenging Because Pandemic, but also snow & (quake-triggered??) avalanches.
Q: Why did so many people feel this earthquake? Isn’t that weird?
A: Eh. How many people are stuck bored at home with absolutely fried nerves paying attention to ANY changes?
The pandemic has us in a state of hypervigilance & eager to take action. Like filling out forms.
A: Eh. How many people are stuck bored at home with absolutely fried nerves paying attention to ANY changes?
The pandemic has us in a state of hypervigilance & eager to take action. Like filling out forms.
Unexpected FAQ: Is it an underground explosion & hidden base collapse?
A: Nope. Explosions & earthquakes have distinctly different seismic signatures.
We’re VERY good at tracking explosions & cavern collapses from monitoring secret weapon testing.
A: Nope. Explosions & earthquakes have distinctly different seismic signatures.
We’re VERY good at tracking explosions & cavern collapses from monitoring secret weapon testing.
Now this is cool!
Earthquake art. The sand was smooth then the earthquake displaced the pendulum.
(I can't fact-check that this is true, but it's plausible.)
Earthquake art. The sand was smooth then the earthquake displaced the pendulum.
(I can't fact-check that this is true, but it's plausible.)
