What about the accelerometers?
I have to take slight issue with the title of this post. It’s easy for people to get confused, but there’s an important, fundamental difference between an “Earthquake Early Warning” system, which is what this is, vs. an “Earthquake Prediction” system, which this most definitely is not. The actual paper clearly describes this as an early warning system.
Early warning systems, which have existed in various forms around the world for years, are not triggered until the earthquake has already initiated, and are meant to provide a few crucial seconds of warning before the shaking arrives to your specific location. The shaking travels outwards from the epicenter at a few miles per second (much slower than an electronic warning) so the area that receives a useful warning is a “doughnut” around the epicenter. Those too close to the epicenter are feeling the shaking before or moments after the warning is triggered, and those beyond a certain distance will get plenty of warning, but experience mild shaking that causes no damage. These systems can potentially be very helpful in preventing a certain amount of injury, but have limits in their usefulness.
The holy grail, of course, is a real prediction system, that would give minutes, hours or days of warning before the quake is felt. Despite a few wild theories out there, no such system appears to be on the horizon. Personally, I don’t think that such a system is physically possible barring incredibly advanced technology that’s we won’t see within our lifetimes.
This is astonishing, because I recall reading back in the 90’s that military GPS was that accurate, but it was dumbed down for civilian use. I assume that changed when I wasn’t looking?
Assuming the movement is not the quake wave (in which case you wouldn’t need any warning besides “the ground is moving”), but a general movement of the ground, It could work if a large enough number of smartphones in the same area detect the same percentage of movement range to the same direction range.
Except, of course, there is a Rihana concert and that many users move to the venue at the same time
I can’t recall the specifics, but I remember hearing about a recent earthquake in California and you could see when and where it happened based on how cell phones woke up in the night from the movement.
Yeah, the original civilian-GPS “jittering” was first turned off during Gulf War I because troops who didn’t have mil-spec units were ordering civilian units via FedEx. (Not to mention Caltech having demonstrated techniques for de-jittering the civilian signal.)
But this system doesn’t just use GPS (which isn’t actually all THAT accurate), it uses GPS (or more precisely, GNSS, the generic term for “Global Navigational Satellite System” — not all of which are GPS), and it also uses the phone’s “INS sensors”, i.e., the Inertial Navigation System sensors — which is to say, the accelerometers and the gyroscope and the software that integrates those into a 3-D inertial nav platform.
Somehow, the mention of “INS sensors” in the published paper was overlooked by some pop-news reporter or other, and now all the bloggers are repeating the (frankly preposterous) claim that GPS alone can do this.
(Also, note that some phones use additional cues - like signal strength from known mapped WiFi hot spots - to improve locational accuracy.)
A GNSS can tell you (approximately) where you are.
An INS can tell you (fairly precisely) where you’ve moved to, relative to where you were.
This system combines both.
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