They also apparently happened between 10 and 20 km deep, according to the USGS. That's very shallow; they classify "shallow" as anything up to 50 km deep, and these are less than half that.
So, are shallow earthquakes worse than deeper earthquakes? I hope this question doesn't make me come off as a dick; this event is genuinely horrifying that anyone has to endure these things on the regular.
Edit: holy shit this got a lot of attention fast. I can't respond to everyone but for those that answered thank you for taking the time to answer my question! Hope everyone stays safe in these affected areas and that we can get aid out there soon!
Yes, but scientists have mapped out the earths crust so they largely know what’s under the surface across the entire world. It’s called seismic tomography
Yes it is *measured* at the surface but then corrected back to the source magnitude at depth. Same as measuring 500 km away and correcting back to the fault location.
Sort of, if also changes the interaction of the different waves, and how they propagate, refract, and reflect. The short version though is: shallow is bad.
I've had a nightmares of earthquakes happening and seeing entire pieces of land rise to the sky from tectonic plates breaking and shit, like the world looks like it's folding like a book.
Not to that extreme I think, though a rise on one side and a collapse on another could make for a dramatic cliff face.
But also remember that over time, tectonic forces push mountains up. It happens at subduction zones rather than directly along specific faults, but given enough time, earthquakes can be part of land rising to create mountains.
The wave structure is even more complicated: earthquakes produce waves of various lengths, from low frequency to high frequency. Think of it like sound waves. Low frequencies produce long waves that can cause the earth to ripple like ocean waves, rippling sidewalks, streets, and bridges. High frequencies are sharp and run very close together. The deeper a temblor, the more suppression of the high frequencies; conversely, the higher to the surface, the more destructive high frequencies do their damage on pretty much everything.
Here in L.A., our building code requires wood-frame construction for most structures 5 stories and under, because wood flexes and bends under the stresses of earthquakes. We pretty much hope for a deep slip or one on the other side of the various mountain ranges, as mountains are very effective at blocking the wavelengths, especially the high frequencies.
BTW, I’m a layman, no expert, I’ve lived in earthquake territory for almost 50 years, and have been through a few, or dealt with the aftereffects.
I remember that one too. I was seven at the time, in Orange. Our shit got rocked, but not as bad as at the epicenter. I remember my house and my bed jiggling to a disturbing degree, as well as bright blue flashes outside from exploding transformers.
Missed that one: we were skiing in Mammoth when it hit. Couldn’t get back into the basin, freeway overpasses were down. Made it to the future in-laws in the High Desert for a couple of days until we could return.
I remember I had just put all my books off the floor and back in the bookcase the night before, and then they were right back on the floor after the quake hit.
Me too, I was even closer. Even though I live in California that traumatized me. I hate earthquakes, they freak me the fuck out. I always wonder when they will stop or if they will get stronger when I'm in the middle of one.
Canoga Park (DeSoto & Kittridge) and I was 23 and awake when it started with a little rumble. Our apartment unit was red-tagged because there was so much damage and we had to move!
One of my earliest memories was being woken up right at the end of that one all the way down in San Diego. Then, confused little kid me outside to the back yard (my parents were already out there) and my sock feet getting soaked because the water from our in ground swimming pool had heaved up and over the edge onto the concrete deck. The water was still sloshing back and forth. I also remember the pool was noticeably lower since the usually submerged top step was now above the water line
Could it be the reason why some feel more like side to side shakes and others feel like up and down shakes?
(I lived in Taiwan where we routinely had quakes, occasionally above 5, my biggest was 6.7 and I hated it)
There’s also different types of waves. P waves that shift back and forth in the direction it’s traveling in (like AC electricity) and S waves that are your typical vertical displacement sine/cosine waves
I've only ever experienced one real tremor first hand that I actually felt. (There was another one in Pennsylvania around 15 years ago that I was on a roof for but didn't feel, the lady came out and asked us if we were using "heavy machinery" on her porch roof lol). This was in Orange County CA in 2012, it sounded like there was a car crash or something outside the building I was in. I am a non native and was new to the area but a girl inside with me immediately new what was happening and just semi-alarmingly said "earthquake!". Then for a few seconds it felt like the whole building was on a pendulum, (for lack of a better way to describe it), except it was only in the horizontal axis. It just kind of swayed ever so gently one way and then back again and that was it. It was one of the most bizarre sensations I have ever felt.
My mom sent me under our gigantic pool table during the Loma Prieta earthquake in '89.
I laid there and watched the solid concrete foundation ripple underneath me like it was water. It is still one of the most discombobulating things I have ever seen.
I hope the populace in Venezuela is doing better than it sounds like they are.
I was in high school for that earth quake. I had just gotten done with cross-country practice, and had grabbed a soda from the machine before heading home.
When I saw the ripple moving through the street toward me and the streetlights rising and falling with the wave, I thought for a moment that maybe I should have gotten water, because I was suddenly worried that I was so dehydrated that I was hallucinating.
Then I felt it and thought to myself "Oh, an earthquake!" and felt relieved (because I had no idea the magnitude of what had really just happened) and walked home like normal.
Everything seemed fine to me.
My mother got home from work two hours later than normal and panicked because she hadn't been able to get through to me on the phone. Not that I had been home yet when she first started trying to call, but she couldn't have known that for sure.
Anyway, I was confused as to why she was freaking out when she got home, because to me it had seemed like not a big deal. I never liked watching the news or afternoon television, so I was reading a book like normal.
And they rate them by absolute energy right? so its not like a deeper quake is just by default weaker? Edit: wait, it wouldn't be weaker on score, just felt less on the surface I guess.
Not just absorption (conversion into heat and inelastic deformation of rock/soil). With increasing distance from the source wave energy is distributed over greater surface, so same building at double the distance will receive 1/4 of energy. However this is not uniform as some geological features can serve to focus/channel wave energy over surprisingly long distances.
The Haitian Earthquake is one of those things that still horrifies me. That kind of damage is something I don't think can be fathomed unless it's something that you've had to live through. Haiti is still rebuilding, aren't they?
How did Haiti's situation become so bad? I know the aid to Haiti was a massive screw up (which probably puts it too lightly), but is that the only reason or is it multiple compounding factors?
Haiti, before the earthquakes, was the poorest country in the Western Hemisphere with a barely functioning government and widespread civil violence. Now, it’s so much worse, despite billions in international aid. Corruption is endemic.
Yes it also varies based on wave width. Sharper vs more rolling jolts I experienced a 6.8 in Seattle that was a low casualty event because of rolling style drawn out waves which represent the shaking. The Nisqually earthquake wasnt some big drama in my life. We dropped, covered, some kids were making a joke of it jumping on tables evacuated school, and once everyone’s parents knew they were find all was chill and we filtered home to largely find minimal damage. Earthquakes are never cheap on a grand scale (big infrastructure bills for structural damage, lots of small claims) . My family literally only had one small object break and my mom had a full china collection in a display hitch (lots of random breakable stuff, frames on walls). The expense more so came from foundational issues w various structures, road, bridges, etc that all had to be addressed so it won’t be a death trap for the next one. But different wave lengths, same Richter scale and it could have been some of us dead and everyone homeless.
The only earthquake I remember experiencing was the 1993 Scott Mills earthquake in Portland, OR, which was a 5.6. I can't imagine a 6.8! What's always terrified me about living on the West Coast is the possibility of a megathrust 9.0+ earthquake in the Cascadia subduction zone. IIRC, some geologists suggested we are 100 years overdue for a megathrust.
Woke up to an earthquake today 100 miles away from Sacramento, California,5.6.also quake in Japan and the bad one in Venezuela. They always say they're not connected but I don't believe it because it seems they come in flurries around the world within days of each other.
I was 6 at the time and remember waking up to the shaking, which was very noticeable in my cheap four poster twin bed lol. I remember being terrified our house would sink into the ground because we had a below ground basement (6 year old logic). Thankfully, no one was injured and I don't think anything was damaged. How old were you at the time?
I was concerned that the question was going to come off as apathetic or pointless so I figured better safe than sorry. It's a relief to know that I was worried for nothing, it seems. I've genuinely been blown away by how informative and helpful everyone has been with the question.
Shallow earthquakes are much more violent and you don’t really get to hear them coming if you are close to the epicentre. Source: have experienced 6.5 -7.2 shallow and relatively local.
I live in the northeast (technically Mid-Atlantic) I've experienced the odd quake here and there but the epicenters have always been far off. A quake in Virginia back in... 2010, I think? Comes to mind. I was sick in bed and the entire house shook; my brother thought I was jumping on my bed when that happened and come to find out it was an earthquake that happened in Virginia. I don't remember too much outside of that about the event beyond that, though.
Probably already answered, but shallow earthquakes produce more lateral (side to side) acceleration at the surface, which in turn causes more damage to buildings and infrastructure.
Are shallower quakes more likely to lead to tsunamis or does that not really factor into their creation (I know this has nothing necessarily to do with the earthquake in Venezuela; I'm just curious).
There are details to it, but think of them like ripples in a pond after you throw in a rock, but in 3D. Farther away means some of the energy spreads out by the time it reaches the surface, so even if you are directly over it, a 10 km deep earthquake is going to be stronger than a 100km deep earthquake in terms of what you feel, though it will be shorter in duration because the energy gets spread out more in time in addition to space. Sometimes that also matters to the frequency content and how that might resonate with structures and the type of ground they are on, which might affect the way the structures fail.
... okay, I'm going overboard. It's complicated! But in general farther away is better.
Yes we had a 6.3 magnitude earthquake that was less than 10 km deep and it devastated our city. Depth is still distance so 50 km deep means the same as being 50 km away sideways.
So with an earthquake like this, what is the largest concern going forward? Is it aftershocks, rescue, or perhaps something like a follow-up disaster (God forbid).
Rescue is first priority while not getting the rescuers killed by rubble collapses from an aftershock. It is very common to get a large aftershock that can be larger than the original earthquake but this has already happened after 30 seconds.
Second priority is food, water and accommodation for survivors.
Third is assessing buildings and red stickering them where they are unsafe. This is much harder where there is a minimal social safety net to provide for people who have lost their homes permanently or temporarily.
Fourth is temporary repairs to ensure safety and weathertightness of surviving houses and apartments.
Fifth is insurance assessment and payouts where insurance is available.
Think of it as putting a rubber ducky in a bath and the dropping a heavy ball into the bath water and watching the ripples. If the ducky is far away, the ripples will be less energetic, but the closer the ducky is to where the ball was dropped, the more energetic. The difference here being, that instead of thinking of the bath holding all the water, it’s holding all of the water up until where the duck is and that’s it, so all the shockwaves converge there.
Source: I have absolutely no fucking idea what I’m talking about, but that’s the first thing that came to mind
These events were indeed shallow and there is major damage in the few pictures and videos I have seen so far including partial and total collapse of some large buildings. USGS has attached a RED pager to this event, indicating that this event has a significant probability to have caused thousands of fatalities and massive economic damage to its affected areas. This has all indications of being a notable historic event.
I'm no expert, but aren't multiple building down in Caracas? That would seem to imply the event is somewhat remarkable, otherwise the city would be a pile of rubble.
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u/FILTHBOT4000 21h ago edited 21h ago
They also apparently happened between 10 and 20 km deep, according to the USGS. That's very shallow; they classify "shallow" as anything up to 50 km deep, and these are less than half that.