Earthquake perception

October 13, 2006 12:43 PM

How often can you feel small earthquakes in Southern California? My girlfriend thinks I'm crazy, but I'm often convinced I've felt a small earthquake. Are there degrees of earthquake perception for different people?

I've lived in Southern California for a little over 2 years now. So far I've only felt one confirmed earthquake. I was in a room with a bunch of people, and we all heard a rumbling and felt a small shake that lasted maybe 3-5 seconds. They all agreed, so I have no doubt that I felt an earthquake.

However, I ocassionally feel very slight movements that I think are earthquakes, but my girlfriend doesn't believe me (she hasn't felt one since we moved here). They are very quick and don't really feel like shaking back and forth, more like a quick lurch in one direction. No noise. It's barely perceptible. I usually check the website of the USGS to confirm, but it never turns out to be an earthquake that is reported on their page. She thinks I've usually just felt rumblings from the highway or something.

Is it possible that what I'm feeling is in fact an earthquake? If so, how come she can never feel them? Are some people more sensitive to slight motions than others? What types of things might give a false positive?

posted by SBMike to science & nature (27 comments total)

"Is it possible that what I'm feeling is in fact an earthquake?"

That's unlikely.

"What types of things might give a false positive?"

It's a truck going by outside.
posted by majick at 12:46 PM on October 13, 2006

I get "false positives" all the time; usually in places that have a parking garage underneath.
posted by mr_roboto at 12:50 PM on October 13, 2006

I usually check the website of the USGS to confirm, but it never turns out to be an earthquake

Doesnt that statement contradict this statement:

Is it possible that what I'm feeling is in fact an earthquake?

I'm confused as to what you are asking.
posted by vacapinta at 12:51 PM on October 13, 2006

I've noticed that in a lot of multistory modern buildings with wide open floorplans (malls, movie multiplexes, airports, etc.), the floor can transmit vibrations very well, and it's possible to feel, for example, a crowd walking by across the room. Or the aforementioned parking garage.
posted by mr_roboto at 12:55 PM on October 13, 2006

Vacapinta, I was thinking maybe the earthquake was too small to have been reported to the USGS. But it's looking like my girlfriend is right. I kind of expected as much.
posted by SBMike at 12:58 PM on October 13, 2006

Ditto on the parking garage thing. The first couple of years I was out here, I thought I was feeling earthquakes all the time.... till I really felt a couple.
posted by scody at 12:58 PM on October 13, 2006

On more than one occasion I've felt a tremor when no one else in the office has. When I appear in their doorway asking "did you feel that?" all I get is a blank look, but then when the USGS website updates to reveal a 3.5 or something, I've been vindicated. So it is possible that you are more sensitive than your girlfriend.

But if what you felt doesn't show up on the USGS website, it was probably just a big truck going by. Alternatively, could it be something going on with your inner ear?
posted by ambrosia at 1:00 PM on October 13, 2006

i've been through a couple of small earthquakes in michigan ... one, i never noticed, although a couple of people i talked to did ... another the fan started rocking a little back and forth on the coffee table ... at first, we thought it was the other person moving feet ... then we thought it was the dog ... then we thought it was a truck, but there wasn't one ... and then, we realized it was a small earthquake ... we were in a trailer on a flood plain ... it's quite possible that we wouldn't have even noticed it somewhere else, in fact, we wouldn't have noticed it at all if it hadn't been for the fan ... (we later confirmed that, yes, it was an earthquake)

so i think it's probable that some people are more sensitive ... it's even possible that one could be in one part of a room and feel it and someone else in the room might not
posted by pyramid termite at 1:01 PM on October 13, 2006

If this bothers you, perhaps you should invest in a seismometer. Or build one.
posted by zennie at 1:02 PM on October 13, 2006

I think it is very possible. I was in NYC years ago and thought I felt an earthquake early one morning. I had been in SF for a "feelable" quake and was certain. My roomie kept saying it was a truck or a subway. Turned out later that day, on the news, it was confirmed. I think some people are attuned to listed maybe because there is some nervousness associated or maybe because it is not something they are used to having not grown up or spent considerable time in an earthquake area.
posted by JohnnyGunn at 1:06 PM on October 13, 2006

Having grown up in L.A. I can tell you without a doubt that some people are more sensitve to slight tremors than others. I, for one, am incredibly insensitive them; there were times when I somehow missed a magnitude four quake.
posted by joedan at 1:09 PM on October 13, 2006

The USGS is very good about detecting and reporting earthquakes. They're very sensitive, looks like down to 1.0 at least which is below the threshold of human detection.
posted by Durin's Bane at 1:20 PM on October 13, 2006

Might also depend on where you're at at the time. I was once at work when a tiny quake hit, and only those of us on the left side of the room felt it. Everyone on the right had no idea.
posted by jenfullmoon at 1:36 PM on October 13, 2006

Growing up in Califormia, I am VERY sensitive to them. I get the same reaction - 'Did YOU feel that?" - Blank stare.

I am a bit freaked out by them as I have had a bad experience, and since that bad experience, I have been even more sensitive to them.

I tell people "When I moved to Texas, I could not sleep - the ground didn't move right." but that is not really true, I don't think anyone is that sensitive.
posted by Monkey0nCrack at 1:39 PM on October 13, 2006

You and my wife should talk. She wandered out of the bedroom the other night and stared at me for a second. Wigged me out. I was all, "what?" -- because I'm eloquent like that. So she asks if I felt the earthquake. She does this occasionally. I said no, USGS site says no.

I don't let it bother me too much. Hey, girls have been telling me they feel the earth move all my life. Yeah, she doesn't laugh at that one, either.
posted by empyrean at 1:41 PM on October 13, 2006

Perhaps use the question (if not earthquakes, is it trucks? Am I imaginaing it?) as an excuse to build your own seismograph (or seismograph kit). Make it into a new hobby :)
posted by -harlequin- at 1:43 PM on October 13, 2006

It is not possible. I regularly (2-3x a year) feel small earthquakes that my girlfriend doesn't feel, but they show up on usgs. The usgs site records earthquakes well below the level of perception.
posted by advil at 1:59 PM on October 13, 2006

Do what I do when I think I've felt an earthquake: check to see if the water in the toilet is moving. I live on a hill, and while there are large trucks going around outside on a regular basis, my apartment is cheap enough that I can hear the engine if they're large enough to simulate a quake.

I perceive quakes maybe a couple times a year, often enough to have looked out the window for trucks and spend a half hour waiting in vain for a seismic report to show up on the USGS site, and the simplest explanation I've been able to derive is that perhaps the fluid in my ears that affects equilibrium is subject to very minor disturbances that can cause the perception of small earthquakes.
posted by rhizome at 2:00 PM on October 13, 2006

If you have allergies, a slight sinus infection or viral-related swelling in your eustachian tubes, the fluid pressure could cause your inner ear balance organs to be more sensitive to movement, vibrations and air pressure changes.

That could account for different people noticing the vibration differently. For example, first born natural birth children tend to have had their heads compacted more during birth, and might therefore be more susceptible to sinus infections, and therefore more likely to have fluid pressure in their ears this time of year.

This is wild speculation, of course. I'm just throwing it out there as a hypothesis ...
posted by Araucaria at 2:19 PM on October 13, 2006

My sense is that it's impossible to feel real ones (as reported by the USGS) which rate less than 4.0 unless you're right on top of the epicenter.

I do feel phantom earthquakes after real ones, for a while. It wears off, eventually. (Truck going by or some other local event is the usual culprit.)
posted by Rash at 3:07 PM on October 13, 2006

Well I think the way people react to them is different - and if they worry you a lot more then you will be more aware of them.

For example I am up now because we just had a mid-size quake here in the Kanto area. I woke up and had jumped into clothes and raced out of the bedroom, whereas I don't think my husband even woke up at all.

I usually check with a light fitting that will move only if there is an actual earthquake and it's not being just me.
posted by gomichild at 3:21 PM on October 13, 2006

When I lived in Tokyo, I always found myself feeling non-existent earthquakes. I think it's because, with Japan being such a seismically active place, I automatically assumed any unexplained tremor or vibration to be a distant earthquake. Perhaps SoCal residents possess similar sensitivities?

Oddly enough, I never really sweated the real earthquakes. I was walking down the street in Akihabara when Tokyo experienced its most powerful earthquake in years, yet I didn't feel a thing. I didn't even realize something was up until I saw fire trucks on the move and returned to the train station to find all services canceled. A month or so later, I was sitting in my office in a highrise when another big earthquake struck, and despite the building lurching every which way and lights swinging above my head, I didn't even rise from my desk.

As for the little ones... those were fun. But I grew up in Texas, where the ground rarely if ever moved.
posted by jal0021 at 3:57 PM on October 13, 2006

OK, crazy question, but are you on anti-depressants, or weaning yourself off of them?

When I phased out my dosages of Effexor, it played havoc with my perceptions, and I would find myself sort of shifting to catch my balance while walking, because it would feel like...well, like I just stepped on a pencil or a skateboard or something, and it felt like my foot shot out from under me for, say, half an inch.

So yes, some pharmaceuticals, once you stop taking them, can cause microspasms that feel like your footing is shifting.
posted by StrangeTikiGod at 4:50 PM on October 13, 2006

I used to notice this sometimes when I was laying in bed before sleep.

I eventually figured out that it was my heartbeat shaking the bed ever so slightly.
posted by Malor at 8:50 PM on October 13, 2006

If the USGS didn't report it, it simply didn't happen. They, unlike you, have the advantage of observing from tens of thousands of places at the same time, and correlating all of that data in real time so as to avoid false positives caused by local things like trucks going by. Further, because their measurements are not taken by people, they're not subject to biases from an individual's level of alertness.
posted by dmd at 4:29 PM on October 14, 2006

I once noticed a quake that was below 4.0. I was in Long Beach at the time. My chair moved just a bit, but also my patio window made a sharp knock. No rock and roll, just one bump. This was about a year after the Wittier quake, which was my first, and I experienced quite fantasticly, since I was near the epicenter, in a big old warehouse.

I also noticed that, after the real shaker of the Wittier, I was quite senstive for a couple years to every little shake--Most of them false positives.

Funny enough, when the Wittier quake hit, my first thought was of a subway (I'd moved from NYC). My 2nd thought was "there is no subway in LA" (true at the time). Third thought: "Get under the desk, you idiot!"
posted by Goofyy at 1:16 AM on October 16, 2006

I started getting false positives after a trio of significant quakes at the end of last year. I have them a lot less now, and they are less startling, but they still happen. Sometimes if I'm attentive I can detect that they were caused by my pulse. Sometimes they're my weight shifting against my weak boxsprings as I breathe. Other times I think it's just a glitch in my vestibular sense or something.

I think it's a learned perception: These same things happened before, but when they did I just ignored them. Now I perceive them as first shocks of an earthquake because I have learned to.
posted by eritain at 1:47 AM on May 12, 2007