Профиль

Also known for: inventing early computers, identifying sea level changes in Italy, proposing life insurance and actuarial tables, and analyzing the pros and cons of property taxes. Among other things.

My guess is that that's pretty normal. I searched the USGS catalog for quarry blasts and found over 2000 events, dating back to mid-2019 (maybe that's when they started reporting them?). I expect the rate may vary seasonally if that affects quarry work.

Hi Judy, thanks for sharing my post! I just want to clarify: ground shaking travels further through hard ground; it amplifies in soft sediment. A single earthquake can have both effects - a wave can travel a long distance through hard rock, then amplify when it reaches a basin of soft sediment.

That deformation can cause faults in the crust to slip, producing earthquakes.

..., slowly pulling the squishy mantle rocks back in underneath. Here's a diagram from the GFZ: www.gfz.de/en/section/e...

...back upward, but it couldn't do it quickly, because the squishy rock underneath couldn't deform that fast. It turns out that even the hot rock of the upper mantle still take a long time to move - thousands of years. The crust has been trying to move back up ever since the ice melted ...

...huge, thick glaciers sat on the surface. I mean, HUGE, like a mile thick. The weight of these glaciers pushed down on the crust. Over time, that weight pushed the squishier deeper rock out of the way (sideways), so the crust sagged down. When the ice melted, the crust tried to rebound ...

Great question! It's kind of like a memory foam mattress: even after you get up, it takes awhile to return to normal. Imagine a cross-section of the Earth's crust and mantle. The upper part is colder and more brittle, but as you go down, the rock becomes hot and squishy. During the ice ages ....

I have not seen imagery like that yet. You don't need to observe evidence of liquefaction in action - the deformation persists after the earthquake, in the form of lateral movement, "sand blows", tilted foundations, etc. These features may be subtle and require more detailed field surveys.

Sure, go ahead.

I don't see evidence of fault slip/rupture in the video - there is some cracking of the ground, but that can be expected more broadly, especially since we know liquefaction was probably pretty widespread.

It's too far away. My guess is shaking-triggered liquefaction. Very impressive!

Sorry - it's sent out by email; there is no public portal for it.

See our follow-up post here: earthquakeinsights.substack.com/p/early-scie...

Early scientific picture of the deadly Venezuela earthquake emergesEastward rupture from the Boconó fault onto the San Sebastián faultearthquakeinsights.substack.com

That sounds possible. I'm not sure how well the fault geometry in the connecting area is known. Some early satellite imaging does show the western end of the rupture lining up with the northern part of the Boconó fault. The offshore section will be trickier, although it's not too far from land.

Ah-ha! The focal mechanism of the M7.2 just got updated: earthquake.usgs.gov/earthquakes/... Now it matches the M7.5.

I find it quite hard to reconcile the USGS focal mechanism of the first event with either the Boconó fault or the San Sebastián fault - I am reserving judgement until more information becomes available (including on whether this is one earthquake or two).

Yes, that would be the idea - eastward propagation of the rupture front, with a reinvigorated pulse of rupture representing the second event. Large earthquakes can usually be decomposed into “sub events”, so that would be the model here.

That model may in part be driven by early back-projection results like this one, which use dense seismic networks far from the epicenter to track the seismic energy released over time. Credit: Prof. Dun Wang’s group at China University of Geosciences, Wuhan; shared by Dr. Baoning Wu at UCSD.

Nope!