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Anticipating Earthquakes
dnahelix writes "Science @ NASA reports 'High above Earth where seismic waves never reach, satellites may be able to detect earthquakes--before they strike.'"
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Interestingly, a 1975 earthquake in China was successfully predicted due in large part to strange animal behavior. A large number of lives were saved.
Needless to say, this is an extreme exception to the rule, and is about as reliable as grandma's old bones are at predicting the weather.
Take the cheese to sickbay, the doctor should see it as soon as possible - B'Elanna Torres, "Learning Curve"
Yes, the Chinese are now downplaying predicting earthquakes after 30 false alarms. See Is the reliable prediction of individual earthquakes a realistic scientific goal?
I saw a TV show about fringe-scientific earthquake predictors. One of the was quite unconvincing, but the other was interesting. He predicted quakes by satellite photos of "earthquake clouds". The finding mentioned in the Science@NASA article about thermal anomalies might back his theory up some. He makes his predictions publicly on his website.
The nice moire pattern in the photo showing changes in elevation was from after the quake. It does a nice job of showing how the stress along the fault was released at this point during a quake, but isn't directly a lot of help in predicting anything. However, one would assume that if you looked at similar photos along a known fault for long enough, there would be areas that did not show any colorfull moire patterns, surrounded by lots of color (indicating movement in the fault). Pretty cool, but I think most of the major faults already have this information from ground measurements.
The "60% chance of earthquakes in the next two days" portion of the prediction seems to rely on some piezo electric effect detected via magnetometers and thermal imaging. This has been speculated about for at least a couple of decades now, but I guess the signal to noise ratio is pretty bad since they haven't declared success yet. Maybe QuakeSat, mentioned at the end of the article, will provide enough comprehensive data to make some useful predictions. Predicting 12 out of the last 3 earthquakes isn't going to win you any friends!
Short term earthquake prediction (hours to weeks) has not been unsuccessful due to lack of effort. After some promising hints in Russia and China in the early 1970s, scientists around the world looked for a systematic precursor. All kinds of things happen before A COUPLE of large quakes: well-level changes, radon gas burps, scared animals, magnetic anomalies, heat anomalies, foreshocks, and so on. The problem has been they have not been systematic and repeatable. Is is not clear whether a GENERAL THEORY OF PREDICTION is even possible then. One hypothesis is that each seismic region may have its characteristic precursors. However, even the most active seismic areas like the San Fernando Valley, Los Angeles experience large quakes tenty years apart, so its not easy to these this second hypothesis.
Mexico City is both cursed and blessed by its earthquake situation. It is built on old lake mud which amplifies seismic waves, making buildings collapse. However, the worst quakes occur on the west coast, which takes seismic waves about five minutes to propagate through the rocks to Mexico City. They've used this delay to install a siren warning system for quakes, so people could leave buildings and turn off power. The first few years it issued too many false alarms, but has worked OK for recent west coast quakes.
A siren system would not work that well in California quakes, because the cities are too close to the earthquake faults for a general warning. However, refineries, power plants, subways, and computer disk farms, all which could react to a 10-30 second warning, are connected to an automatic warning system run by a jopint government corporate progam.
If you are interested in knowing more about earthquake hazards, but you're not a seismologist, check out Earthshaking Science by Susan Hough. She works for the U.S. Geological Survey. She first discusses the basics of determining earthquake hazard, then discusses the currently estimated hazard in various regions in the United States. She's not optimisitic about specific earthquake prediction, but she thinks that we can improve our estimates of longer-term hazards. These estimates are critical for guiding hazard-mitigation efforts (building codes, for example).
A good number of volcanoes - such as those on Hawaii, are fitted with tiltmeters and laser-ranging reflectors.
As magma moves up towards the surface, some volcanoes start to 'inflate', bulging outwards. By measuring changes in tilt, and the geometry of the mountain, vulcanologists can get some warning of the changes under the mountain.
They usually combine this with seismic evidence (that moving magma creates swarms of tiny 'quakes), changes in gas production and the like to try and predict eruptions.
However, volcanoes are just as unpredictable. The USGS made a series of predictions about the Long Valley Caldera in Eastern California. It is an ENORMOUS crater which is underlain by an active magma chamber. The last volcanic activity in the region was about 400 years ago, and it is likely to continue into the future. Slap bang in the middle of Long Valley is the Mammoth Mountain ski resort, built around a dormant volcano.
In the early 1980s, the area around Mammoth Mountain began to bulge, molten rock was being forced upwards, there were swarms of 'quakes, trees began dying as CO2 bubbled up from underground. The USGS cautiously announced that they expected Mammoth Mountain to become active in the near future.
It didn't. The area remains highly active, but doomsday was put off for now.
BTW. if you ever get a chance to go to Mammoth Mountain, Long Valley and the Inyo Craters, do take it - the landscape is simply awe-inspiring.
Another example is Pozzuoli, which lies West of Naples in an area known as the Phlaegrean Fields. This is another colossal caldera with an active magma chamber. The last eruption was in 1538 when a new mountain (called Monte Nuovo somewhat unoriginally) was formed, the crater of Solfatara is still somewhat active, disgorging water and sulphurous fumes.
Pozzuoli is in the the middle of the Fields, a nice seaside town with some Roman ruins. However, during the 1970s, the area began to be shaken by hundreds of 'quakes a day. Even more worryingly, the area began to bulge upwards, sometimes by a centimetre a day! The Italian government ordered the evacuation of the entire city for several years, fearing another massive eruption. Eventually, the bulge subsided, the 'quakes faded and the people went back. But millions had been spent and enormous social dislocation caused.
It's quiet there at the moment, so everyone is looking East, over Naples to Vesuvius, which has been suspiciously quiet for far too long now.
Best wishes,
Mike.
At Yellowstone, one of the world's largest volcanoes, there are indications that something is going on. There's a big bulge on the bottom of Yellowstone Lake, but nobody is sure how long it's been there. It's emitting lots of hot water, though, and there is plentiful evidence of large hydrothermal (i.e. superheated steam) eruptions in Yellowstone's recent past. Also, trails in Norris Geyser Basin have been closed because the ground temperature is near 200 degrees Farenheit. While this is probably hydrothermal, not magmatic, activity, if Yellowstone ever does decide to have another major eruption (as it last did 600K years ago), you can pretty much count on massive worldwide social disruption. Ever wonder what it would be like if all food production in the western U.S. were to go away?