So far, however, earthquake prediction has proved an elusive art: no one has worked out how to read Earth's vital signs to provide accurate warnings. But there is hope. Among the welter of dead ends - from monitoring animal behaviour to measuring radioactive gas emissions or the flow of groundwater - a new bellwether is coming to the fore: electromagnetic radiation.

Prior to some recent quakes, scientists have detected electromagnetic pulses emanating from the ground and electromagnetic disturbances in the ionosphere, the planet's tenuous envelope of charged particles extending from about 80 to 1000 kilometres up. "There are definitely hints of something [electromagnetic] happening in the region of earthquakes before the earth moves," says Colin Price, a geophysicist at Tel Aviv University in Israel.

Price and others have been working in quake-prone regions in California, Japan and Russia. At a meeting of the International Union of Radio Science (URSI) in New Delhi, India, in October, he and his colleagues speculated that as underground stresses build up, rocks containing magnetic particles begin to fracture, generating ultra-low-frequency (ULF) radio waves - below 1 hertz - as they are torn apart. Detect these radio waves, suggest the researchers, and you might have the makings of a prediction system. (Scientists are now also studying how animals can hear ULF and react to it quickly, since no animals were killed in the Indonesian tsunami a year ago. Order the DVD from www.pbs.org 800-336-1917 "Can Animals Predict Disaster?" - Ed. note)

Some research groups are already tunnelling underground to pick up radio pulses in the ULF range, while others are using sensor-stuffed satellites to measure radio disturbances in the ionosphere above quake-prone regions. Because there have been many false dawns in earthquake prediction, Price is cautious. "But if the chances are one in a hundred that we succeed, the huge benefits of success make this research worth continuing," he says.

Quakes' telltale radio signals were first rumbled almost 20 years ago, following an accidental discovery by Anthony Fraser-Smith of the Space, Telecommunications and Radioscience (STAR) Laboratory at Stanford University in California. During the Loma Prieta earthquake that hit the San Francisco area in October 1989, Fraser-Smith was monitoring electromagnetic noise at frequencies up to 10 hertz. He noticed the electromagnetic noise increased almost 20-fold for two weeks before the earthquake - and continued at that level about a month afterwards. It peaked 3 hours before the quake, between 0.01 and 0.5 hertz.

Since then, others have tried to make similar measurements in seismically active regions. Groups in Japan and Russia have observed similar signals to Fraser-Smith's, but for up to one or two months before a quake. Could this be the long-sought early warning of seismic catastrophe?

Minoru Tsutsui at Kyoto Sangyo University in Japan is trying to find out. His team has bored a hole 100 metres deep and 10 centimetres wide in a back lot on the campus. They placed one directional ULF antenna at the bottom of the hole and another above the ground. The relative strengths of any ULF signals detected at the two antennas allow the team to work out which direction the pulses come from.

On 4 January 2004 the system began detecting ULF radio pulses coming from the south-east. Two days later, a magnitude-5.5 quake struck the area, with an epicentre 130 kilometres away - to the south-east. Six hours after the quake, the ULF signals spread out, arriving from both the south-east and south-west, and died off the next day.

Since then, the Kyoto team has discovered that this effect is only detectable above a certain threshold quake strength (Geophysical Research Letters, DOI: 10.1029/2005GL023691). Tsutsui now wants to investigate the mechanism that produces these ULF radio pulses. Until we know this, he says, "we cannot easily predict where the epicentre will be".

Meanwhile, Price's team is collecting data from inside a 175-metre-deep, 3-metre-wide tunnel dug into the rift valley between the Dead Sea and Eilat in Israel, an area that frequently experiences tremors up to magnitude 6. But so far, they have had little luck. "Since 2003, we have not had any large events within 100 kilometres of our station," says Price. None of the earthquakes has been stronger than magnitude 4.4, which doesn't appear to be intense enough to generate the telltale ULF pulses.

They may not be measurable in any case, says Masashi Hayakawa, an electronics engineer at the University of Electro-Communications in Tokyo, who has strong reservations about Tsutsui's conclusions. He points out that all kinds of natural phenomena produce ULF signals - thunderstorms, solar activity and meteors among them - and thinks Tsutsui won't be able to pick out ULF signals caused by imminent earthquakes from the noise.

Hayakawa thinks the atmosphere holds the answers: he measured ionospheric disturbances between 3 and 30 kilohertz a few days before Japan's 1995 Kobe quake. And Michel Parrot of France's National Council for Scientific Research (CNRS) in Orleans agrees. He points to preliminary data from a European Space Agency satellite called the Detector for Electromagnetic Emissions Transmitted from Earthquake Regions (DEMETER). Using a battery of sensors that measure the temperature, density and composition of the ionosphere, DEMETER measured an increase in ion density and temperature of the ionosphere seven days before a quake of magnitude 7 hit Japan's Kii peninsula on 5 September 2004.

This year it observed similar disturbances two days before the 23 January quake in Indonesia and five days before a quake on 30 August near Japan, and last November two days before a quake close to New Zealand.

As luck would have it, DEMETER was turned off during the 26 December 2004 Asian tsunami quake off Sumatra and the quake in Kashmir on 8 October this year, so it captured no data on these two events, Parrot says.

Ian Main, a seismologist at the University of Edinburgh, UK, believes the ULF and ionospheric findings are intriguing, but not yet convincing enough to establish a link to earthquakes. To do that, a far larger number of quakes must be examined, he says.

Weblinks

• International Union of Radio Science
• http://www.ursi.org
• Geophysics research, Tel Aviv University
• http://geophysicis.tau.ac.il/programs/geophysics.asp
• DEMETER, CNES
• http://smsc.cnes.fr/DEMETER/

First, there is a rich history of RF (J. Geophys. Res. 87, B4, 2851-2859, 10 April 1982), LF and ELF (J. Geomag. Geoelectr. 38, 1031-1040, 1986) as well as ULF magnetic signals (Tectonophysics, 6 (1) 1968, 59-68 and Geophysical Research Letters, 17, 9, August, 1990) preceding the onslaught of earthquakes. Secondly, Professor Emeritus Elizabeth A. Rauscher (U. of Nevada) has worked out how to read the Earth’s vital signs to provide accurate warnings of impending earthquakes and volcanic eruptions and even patented the triangulating magnetic coil instrumentation (US #4,724,390) back in 1988. Her invention is based on the changes in appearance and amplitude of specific ELF frequencies found to be characteristic of an area, from the local tectonic plate piezoelectric stresses prior to earthquake/volcanic events. Once these are identified by the trained operator, Dr. Rauscher points out in her new book, they can then pinpoint the epicenter (from triangulation of three widely spaced coil signals) and give significant advance warning prior to the seismic event.

The most dramatic prediction, for which she is most famous, is documented as follows: “During the University of California, Irvine International Workshop on Low Frequency Electrical Precursors, Lake Arrowhead, CA, sponsored by the USGS and NSF on June 14-17, 1992, one of us (E.A.R.) announced our prediction of a large, greater than 7 event in the region of the conference.* On June 27, 1992, the Landers 7.5 event east of Los Angeles occurred.” This two-week advance notice of an impending earthquake is published in Electromagnetic Phenomena Related to Earthquake Prediction by Hayakawa et al., (Bise & Rauscher, “Ambient Electromagnetic Fields as Possible Seismic and Volcanic Precursors” Terra Sci. Pub. Co., Tokyo, 1994, p. 221 - 242). The ironic and synchronistic nature of the predicted earthquake event, right in the midst of the world's open-minded but unconvinced geologists, cannot be overemphasized. Another decade had to pass before the topic of earthquake prediction is a leading news item in scientific journals once again. However, trial and error still is the best technique for those unfamiliar with the Rauscher predictive protocol.

Dr. Rauscher’s book on her well-documented, scientific technique for earthquake prediction is scheduled for release in Spring, 2006. However, as the outspoken Haroun Tazieff, former Director of Research at the French National Scientific Research Center, states in his 20-year old McGraw Hill book, Earthquake Prediction (ISBN 0-07-62992-7), there is an unexplainable psychological inertia and politically motivated delay in using the prediction technology he and others have pioneered over the years.

Integrity Research Institute publishes a comprehensive report which includes a complete reprint of Dr. Rauscher's pioneering article mentioned above. The title of the report is "Earthquake Predictions with ELF Magnetometer" - report # 201. Order online: http://users.erols.com/iri/orderAll.html .

For more information, contact Dr. Elizabeth Rauscher, 3500 S. Tomahawk, Bldg, 188, Apache Junction, AZ 85219, phone: 480-982-2285.

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* NOTE: "USGS" is the US Geological Survey www.usgs.gov ; "NSF" is the National Science Foundation www.nsf.gov  - Ed. note

7) Earthquake Alarm

It seems that earthquakes should be predictable. After all, we can predict hurricanes and floods using detailed satellite imagery and sophisticated computer models. Using advanced Doppler radar, we can even tell minutes ahead of time that a tornado will form.

Accurate earthquake warnings are, at last, within reach. They will come not from the mechanical phenomena—measurements of the movement of the earth's crust—that have been the focus of decades of study, but, rather, from electromagnetic phenomena. And, remarkably, these predictions will come from signals gathered not only at the earth's surface but also far above it, in the ionosphere.

For decades, researchers have detected strange phenomena in the form of odd radio noise and eerie lights in the sky in the weeks, hours, and days preceding earthquakes. But only recently have experts started systematically monitoring those phenomena and correlating them to earthquakes.

A light or glow in the sky sometimes heralds a big earthquake. On 17 January 1995, for example, there were 23 reported sightings in Kobe, Japan, of a white, blue, or orange light extending some 200 meters in the air and spreading 1 to 8 kilometers across the ground. Hours later a 6.9-magnitude earthquake killed more than 5500 people. Sky watchers and geologists have documented similar lights before earthquakes elsewhere in Japan since the 1960s and in Canada in 1988.

Another sign of an impending quake is a disturbance in the ultralow frequency (ULF) radio band—1 hertz and below—noticed in the weeks and more dramatically in the hours before an earthquake. Researchers at Stanford University, in California, documented such signals before the 1989 Loma Prieta quake, which devastated the San Francisco Bay Area, demolishing houses, fracturing freeways, and killing 63 people.

Both the lights and the radio waves appear to be electromagnetic disturbances that happen when crystalline rocks are deformed—or even broken—by the slow grinding of the earth that occurs just before the dramatic slip that is an earthquake. Although a rock in its normal state is, of course, an insulator, this cracking creates tremendous electric currents in the ground, which travel to the surface and into the air.

We can detect such electromagnetic effects in a number of ways [see illustration, "Signs of Quakes to Come"]. Earthquake forecasters can use ground-based sensors to monitor changes in the low-frequency magnetic field. They can also use these instruments to measure changes in the conductivity of air at the earth's surface as charge congregates on rock outcroppings and ionizes the air.

Using satellites, forecasters can monitor noise levels at extremely low frequency (ELF)—below 300 Hz. They can also observe the infrared light that some researchers suspect is emitted when the positive holes migrate to the surface and then recombine with electrons.

Scientists around the world are looking at all of these phenomena and their potential to predict earthquakes accurately and reliably. One group is at QuakeFinder, a Palo Alto, Calif.­based company cofounded by one of us, Bleier, in 2000. QuakeFinder researchers have begun directly monitoring magnetic field changes through a network of ground-based stations, 60 so far, in California [see photo, "Earthquake Investigator"]. In 2003, the company joined forces with Stanford and Lockheed Martin Corp.'s Sunnyvale, Calif., center to launch an experimental satellite designed to remotely monitor magnetic changes. A larger, more sensitive satellite is in the design stages. QuakeFinder hopes to develop an operational earthquake warning system within the next decade.

The 1989 Loma Prieta earthquake near San Francisco sent out strong signals of magnetic disturbances fully two weeks before the 7.1-magnitude quake occurred. The idea that such signals existed was still a new one then, certainly not well enough accepted to justify a decision to issue a public warning.

We happen to have excellent data from that quake. Stanford professor Anthony C. Fraser-Smith had buried a device called a single-axis search-coil magnetometer to monitor the natural background ULF magnetic-field strength at about 7 km from what turned out to be the center of that quake. He selected this spot simply because it was in a quiet area, away from the rumblings of the Bay Area Rapid Transit trains and other man-made ULF noise. He monitored a range of frequencies from 0.01 to 10 Hz, essentially, the ULF band and the lower part of the ELF band.

On 3 October, two weeks before the quake, Fraser-Smith's sensors registered a huge jump in the ULF magnetic field at the 0.01-Hz frequency—about 20 times that of normal background noise at that frequency. Three hours before the quake, the 0.01-Hz signal jumped to 60 times normal. Elevated ULF signals continued for several months after the quake, a period rife with aftershocks, and then they disappeared.

The Loma Prieta quake was a stunning confirmation of the value of ULF signals in predicting earthquakes. This validation of the theory prompted Bleier to establish a network of earthquake sensors in the Bay Area, an effort that grew into QuakeFinder.

Other researchers around the world who monitored changes in the magnetic field at ULF frequencies had noticed similar, but not as extreme, changes prior to other events. These observations occurred shortly before a 6.9-magnitude quake in Spitak, Armenia, in December 1988 and before a devastating 8.0-magnitude earthquake in Guam in August 1993.

Author Bleier recorded spikes of activity, four to five times normal size, in the 0.2- to 0.9-Hz range for 9 hours before a 6.0-magnitude earthquake in Parkfield, Calif., on 28 September 2003. Solar storms sometimes cause ripples in the magnetic field at those frequencies, but there had been no appreciable solar activity for six days prior to the quake.

In Taiwan, sensors that continuously monitor Earth's normal magnetic field registered unusually large disturbances in a normally quiet signal pattern shortly before the 21 September 1999 Chi-Chi, Taiwan, earthquake, which measured 7.7. Using data from two sensors, one close to the epicenter, and one many kilometers away, researchers were able to screen out the background noise by subtracting one signal from the other, leaving only the magnetic field noise created by the imminent earthquake. Two teams, one in Taiwan and one in the United States, calculated that the currents required to generate those magnetic-field disturbances were between 1 million and 100 million amperes.

Besides detecting magnetic-field disturbances, ground-based sensors can record changes in the conductivity of the air over the quake zone caused by current welling up from the ground. These sensors can vary in form, but those we use are made from two 15-centimeter by 15-cm steel plates locked into position about 1 cm apart. A 50-volt dc battery charges one plate; the other is grounded. A resistor and voltmeter between the battery and the first plate senses any flow of current.

Normally, the air gap between the plates acts as an insulator, and no current flows. If, however, there are charged particles in the air, a current begins to flow, creating a voltage drop across the resistor that registers with the voltmeter. The currents created in this way are not large—on the order of millivolts—but are detectable.

Last year QuakeFinder installed 25 ELF detectors with such air- conductivity sensors in California's Mojave Desert to determine if increased air conductivity actually precedes earthquakes and contributes to the formation of the so-called earthquake lights [see photo "Mysterious Lights"]. But to date, no large earthquakes have struck near these sensors, so no data are available yet.