QuakeFinder: Is earthquake prediction finally a reality?
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Serendipity shows the way during Loma Prieta quake
While scientists concentrated primarily on potential seismic precursors to quakes, anecdotal reports of other odd goings-on before earthquakes are common. As far back as ancient Greece there have been reports of animals behaving strangely before a quake. Recent research in Germany has even documented ant colonies modifying their behavior pre-quake.
Eyewitness videos of light emerging from the ground prior to an quake — so-called “earthquake lights” — inspired QuakeFinder founder Tom Bleier to see if he could track down the electromagnetic signals responsible and possibly use them to predict earthquakes. His homebrew efforts weren’t sophisticated enough to pick out anything interesting, but he was re-energized by an event that occurred nearby on the central California coast.
In 1989 a Navy-funded Stanford magnetometer looking for ultra-low frequency (ULF) signals recorded sizable electromagnetic (EM) activity prior to the nearby Loma Prieta earthquake. As a result, Bleier was inspired to redouble his informal efforts. After persevering on his own, ten years later Bleier began QuakeFinder — a formal effort to build a network of sensors that could record EM pulses and other possible precursors to earthquakes.
Its initial sensor units were fairly simple, but the current tenth generation model includes sensors for various frequencies of electrical and magnetic disturbances, as well as ionization, seismic and other sensors. One of the hardest parts of collecting this type of data is filtering out irrelevant information caused by nearby trains, trucks, electric cattle fences and even weather patterns. In addition to selecting isolated sites and burying the magnetometers, the data from the network of sensors and satellite data are combined to allow selecting out signals that might be related to potential earthquakes.
How QuakeFinder works
While traditional earthquake monitoring relies on seismographs, which measure physical movement in the ground, it turns out that sufficient stress on rocks causes them to emit magnetic pulses. The currents created can be massive, around 100,000 amps for a magnitude 6 quake, and over a million amps for one that is over 7. The ultra-low frequency component of those pulses is capable of traveling miles through the rock, making it feasible to measure with a network of monitoring stations.
While these short pulses occur on a regular basis — perhaps ten or so on a normal day — QuakeFinder sensors have recorded unusually high concentrations of them in the hours and days prior to earthquakes — well over 100 per day — even after filtering out spurious pulses from nearby lightning or other large electrical sources.
While it isn’t clear exactly which of several possible theories explain the magnetic pulses, their existence can be verified by stressing a large rock to the breaking point, like in the pictured experiment QuakeFinder conducted by stressing a seven ton boulder until it fractured. However, the large, dry, boulders used in experiments aren’t the same as the brine-soaked rock at earthquake depth. So there is plenty of room for speculation on how things are really working miles down where a typically quake gets its start.
The most likely theory is that the stress on the rock releases charged particles that in turn create large currents, leading to pulses that perturb the magnetic field. The pulses can also reach the surface, causing the appropriately named earthquake lights, as well as increased ionization and infrared radiation — which QuakeFinder has added to its list of monitored conditions. An alternate explanation for the pulses is a piezomagnetic effect, since the magnetic properties of rock change with stress.
Next page: QuakeFinder comes of age…