Ambient Power Module

Joe Tate's Ambient Power Module (APM) converts radio frequencies to usable electrical power (albeit only milliwatts) sufficient to operate clocks, smoke alarms, Ni-Cd battery chargers, &c. It also can provide early seismic warning since earthquake preparation generates radio frequencies. It also acts as a proximity detector for ships & structures.

The Amazing Ambient Power Module
Radio Waves Singal Earthquakes
Radio Earth: The Radio-Seismic Connection
US Patent # 4,628,299: Seismic Warning System Using RF Energy Monitor

The Amazing Ambient Power Module

Copyright 1989 Ambient Research

Parts List for the APM-2

Four 1N34 germanium diodes (Radio shack #276-1123) ~ Figure 1, X1, X2, X3, & X4
Two 0.2 mfd 50 V ceramic capacitors ~ Figure 1, C1 & C2
Two 100 mfd 50V electrolytic capacitors (Radio Shack #272-1016) ~ Figure 1, C3 & C4
Copper wire for antenna & ground connections


The Ambient Power Module (APM) is a simple electronic circuit which, when connected to antenna and earth ground, will deliver low voltage up to several milliwatts. The amount of voltage and power will be determined by local radio noise levels and antenna dimensions

Generally a long wire antenna about 100' long and elevated in a horizontal position about 30' above ground works best. A longer antenna may be required in some locations. Any type copper wire, insulated or not, may be used for the antenna. More details about the antenna and ground will be discussed further on.

The actual circuit consists of two oppositely polarized voltage doublers (Figure 1). The DC output of each doubler is connected in series with the other to maximize voltage without using transformers. Single voltage doublers were often found in older TV sets for converting 120 VAC to 240 VDC. In the TV circuit the operating frequency is 60 Hz.

The APM operates at radio frequencies, receiving most of its power from below 1 MHz. The basic circuit may be combined with a variety of voltage regulation schemes, some of which are shown in Figure 2. Using the APM-2 to charge small NiCad batteries provides effective voltage regulation as well as convenient electrical storage. This is accomplished by connecting the APM-2 as shown in Figure 2B.

Charging lead acid batteries is not practical because their internal leakage is too high for the APM to keep up with. Similarly, this system will not provide enough power for incandescent lights except in areas of very high radio noise.

It can be used to power small electronic devices with CMOS circuitry, like clocks and calculators. Smoke alarms and low voltage LEDs also can be powered by the APM.

Figure 3 is a characteristic APM power curve measured using various loads from 0-19 kOhm. This unit was operating from a 100' horizontal wire about 25' high in Sausalito CA. As can be seen from the plot, power drops rapidly as the load resistance decrease from 2 kOhm. This means that low voltage, high impedance devices, like digital clocks, calculators and smoke alarms are the most likely applications for this power source. Some applications are shown in Figures 4 through 7.

Figure 4 ~ A digital clock is shown powered by the APM-2. The 1.5 volt clock draws 28 microamps. Its position on the power envelope curve would be off the scale to the right and almost on the bottom line, dissipating only 42 microwatts.

Figure 6 shows a clock which has the APM-2 built into it so it is only necessary to connect the antenna and ground wires directly to the clock. The antenna for this clock, which is a low frequency marine type, is shown in Figure 7.These antenna are expensive, not generally available, and usually don't work any better than the long wire mentioned above. But it may be necessary to use them in urban areas where space is limited and radio noise is high.

Building the Module

The builder has a choice of wiring techniques which may be used to construct the module. It may be hand wired onto a terminal strip, laid out on a bread board, experiment board, or printed circuit. Figure 8 shows some of the different ways of constructing the APM-2.

Figure 8A is constructed on a screw strip terminal; Figure 8B is constructed on a perforated breadboard; Figure 8C is built on a standard experiment board; Figures 8D, 8E, and 8F are all printed circuits; Figure 8F is made up on a solder strip terminal.

If you wish to make only one or two units, hand wiring will be most practical, either on a terminal strip or breadboard. Assembly on the terminal strip (Figure 8A) can be done easily and without soldering. It is important to get the polarity correct on the electrolytic capacitor. The arrow printed on the side of the capacitor points to negative.

Figure 9 is a closer view of the terminal strip with an illustration of the components and how they are connected.

The breadboard unit is shown in Figure 10 with all components on one side and all connections on the other. All you need is a 2" x 2" piece of perforated breadboard (Radio Shack #276-1395) and the components on the parts list. Push component wires through the holes and twist them together on the other side. Just follow the pattern in the photo, making sure to observe the correct polarity on the electrolytic capacitors and the diodes. The ceramic capacitors may be inserted in either direction.

The experiment board unit is assembled by simply pushing the component leads into the board as shown in Figure 11. This unit is powering a small red LED indicated by the arrow.

The solder strip unit is made up on a five terminal strip. The antenna connection is made to the twisted ends of the ceramic capacitors. When soldering the leads of the 1N34 diodes, care must be taken to avoid overheating. Clip a heat sink onto the lead between the diode and the terminal as shown in Figure 12.

It is beyond the scope of this pamphlet to show how to make printed circuits, but the layout of the board is provided in Figure 13.

Figure 14 shows the front and back view of the completed printed circuit.

A small switch may be installed on the board to activate the zener regulator (Figure 15). This board was designed for use in clocks.

Antenna Requirements

The antenna needs to be of sufficient size to supply the APM with enough RF current to cause conduction in the germanium diodes and charge the ground coupling capacitors. It has been found that a long horizontal wire works best. It will work better when raised higher. Usually 20-30 feet is required. Lower elevations will work, but a longer wire may be necessary.

In most location, possible supporting structures already exist. The wire may be stretched between the top of a building and some nearby tree or telephone pole. If live wires are present on the building or pole, care should be taken to keep your antenna and body well clear of these hazards.

To mount the wire, standard commercial insulators may be sued as well as homemade devices. Plastic pipe makes an excellent antenna insulator. Synthetic rope also works very well, and has the advantage of being secured simply by tying a knot. It is convenient to mount a pulley at some elevated point so the antenna wire may be pulled up to it using the rope which doubles as an insulator (Figure 16).

Figure 17 is an illustration of a horizontal wire antenna using a building and tree for supports.


Usually a good ground can be established by connecting a wire to the water or gas pipes of a building. Solder or screw the wire to the APM-2 ground terminal. In buildings with plastic pipes or joints, some other hookup must be used. A metal rod or pipe may be driven into the ground in a shady location where the earth usually is damper. Special copper coated steel rods are made for grounds which have the advantage of good bonding to copper wire. A ground of this type usually is found within the electrical system of most buildings.

Conduit is a convenient ground provided that the conduit is properly grounded. This may be checked with an ohmmeter by testing continuity between the conduit and system ground (ground rod). Just as with the antenna, keep the ground wire away form the hot wires. The APM's ground wire may pass through conduit with other wires but should only be installed by qualified personnel.

Grounding in extremely dry ground can be enhanced by burying some salts around the rod. The slats will increase the conductivity of the ground and also help retain water. More information on this subject may be found in an antenna handbook.

Good luck getting your Ambient Power Module working. It is our hope that experimenters will find new applications and improve the power capabilities of the APM.

Science News [date unknown]

Radio Waves Signal Earthquakes

From the bright flashes reported to appear in the sky during strong earthquakes to computer breakdowns during severe tremors, scientists have long suspected that seismic activity is associated with a variety of electrical effects. Recently researchers have been taking a careful look at this link, with an eye toward using it to predict earthquakes.

One such study is being conducted by Joseph Tate of Ambient Research in Sausalito, CA, and William Daily at Lawrence Livermore National Laboratory in Livermore, CA. With a system of radio wave monitors distributed along California's San Andreas fault, the researchers have recorded two kinds of changes in atmospheric radio waves prior to earthquakes that occurred between 1983 and 1986.

The most common change is a drop in the radio signals that normally pervade the air as a result of lightning and human sources such as car ignition systems and electric power grids. This reduction typically occurs one to six days before an earthquake and can last for many hours. For example, a magnitude 6.2 earthquake that shook Hollister CA in April 1984 was preceded six days earlier by a 24-hour drop in radio signals being monitored 30 miles from the quake's epicenter. Tate and Daily have found that the larger the earthquake, the longer the time between the radio wave depression and the quake.

Laboratory studies have shown that the electrical conductivity of rocks increases as they are stressed. Based on this and their electrical modeling of the ground, Tate and Daily think the increased conductivity of stressed rocks near the fault causes more radio waves to be absorbed by the ground rather than their traveling through the air. They also plan to test a possible link between radio wave drops and the emission of radon gas, which itself is thought to be a quake precursor. The radon may ionize the air, making it temporarily more absorptive than the detector antenna.

The researchers have also found, in addition to these drops, another prequake phenomenon in which short pulses of increased radio wave activity are emitted. For example, five days before the magnitude 6.5 earthquake hit palm Springs CA in July 1986, a station 15 miles from the epicenter detected a rise in radio signals. This sort of emission is consistent with laboratory work showing that cracking rocks release electromagnetic signals.

Tate says that in their first attempts at predicting earthquakes in 1984 and 1985, they did not miss a single event, so he his optimistic about using this technique for short-term forecasting of San Andreas quakes. "In three to five years", he says, "we should be able to issue [earthquake] warnings."

Whole Earth Review (Fall 1990, pp. 101-104)

Radio Earth: The Radio-Seismic Connection


Joe Tate

Since the earliest days of radio research, many people have thought of these invisible waves as artificial, an effect created solely by wizards in a laboratory. Later, in the 1930s, Karl Jansky discovered radio emissions coming from the Milky Way. Stars are now known to be giant transmitters, broadcasting a spectrum of electromagnetism from low-frequency noise to gamma rays. So much for the artificiality of radio.

Even in the 19th century, in the days of Tesla and Edison, radio noise caused by lightning was known to have recognizable propagation patterns. It was these patterns that Jansky was measuring when he discovered cosmic radio.

Tesla actually calculated the resonant frequency of the Earth, and proposed that electromagnetic waves of this frequency (6-8 Hz) should be generated by the planet from the action of lightning. These "Schumann resonances", as they came to be known, were finally detected in the 1960s.

Other strange radio emissions were noticed at about the same time, a time when many new radio observatories were starting operation at various places around the world. The observatories could each detect and record a wide range and volume of electromagnetic radiation (EMR). Before and during the great Chilean earthquake of 1960, unusual strong signals were received at six widely scattered radiotelescopes. The connection between these radio signals and the earthquake was eventually shown by James Warwick of the University of Colorado, who analyzed the observatories' separately recorded data (Figure 1) [Not shown]. Earthquakes generate radio waves! But how?

Twenty-two years later, after performing a series of laboratory experiments in which rocks were crushed in powerful presses and the resulting electromagnetic emissions were measured, Warwick's paper describing the phenomenon appeared in the April 1982 issue of the Journal of Geophysical Research.

In the meantime, other experimenters had recorded similar effects in Japan, France, the United States and the Soviet Union. Several studies of satellite data revealed marked increases in very-low-frequency (VLF) emissions from epicenter regions before and during major earthquakes. In Greece, researchers found that telluric currents (natural currents of electricity flowing in the Earth) fluctuated prior to earthquakes.

Ambient Power

In 1979, I was experimenting with methods of turning radio energy in the air into usable electric power. I developed a clock which drew its power from an antenna that was just a long piece of wire stretched out horizontally about 20 feet above the ground.

The power supply for the clock worked something like an old-style crystal radio, except that it did not have a tuning circuit. Because of this, the Crystal Clock (as I called it) was able to absorb a wide spectrum of radio noise from the antenna and yield electric power. The power supply was able to deliver much more current than was developed in a crystal radio, although its output was still just a few millivolts.

In the early 80s I demonstrated the clock to the late Frank Oppenheimer, then director of San Francisco's Exploratorium, where I worked in the exhibit repair shop. Oppenheimer suggested recording the power supply's output over a long period of time to determine its dependability. After all, the device relied completely on whatever stray signals happened to be in the air.

Using an Atari computer which had been donated to themuseum, the oputput of the clock's power supply was measured continuously and recorded on floppy disk. This was done by feeding the unregulated voltage output direcly into the coputer's joystick port.

I began calling this power supply the "Ambient Power Module" (APM) because it extracted power from ambient background radio noise. This small circuit, when connected to antenna and ground, used the potential difference between air and ground to generate a small direct current continuously.

As we studied the recorded data, mild fluctuations were noted in a daily cycle. The patterns were consistent over long periods of time, though they differed in different locations. Aside form that, the APM looked like a very dependable source of power. Until the spring of 1984.

On April 24, 1984, a 6.0 magnitude earthquake struck about 90 miles from the APM recording station in Sausalito. Days later, while looking through the data, I noticed that the APM output dropped to less than half its normal value for several hours during the afternoon 6 days before the earthquake (Figure 2) [Not shown] this was very peculiar, because most of the APM's power came from broadcast signals, and broadcasting stations hadn't done anything different that afternoon. Apparently something had temporarily depressed the propagation of radio waves. At high frequencies, such effects can be caused by atmospheric conditions. But the lower frequencies involved here are hardly affected, particularly not the signals from the nearest stations, which account for most of the power received. It was tempting to think this strange radio depression might somehow have been a precursor to the earthquake.

Several smaller quakes had occurred in the area during the year before. Perhaps these also were preceded by similar radio anomalies. Looking back through the accumulated data on the APM's power output, indeed, smaller, less obvious radio depressions were found to occur prior to the lesser earthquakes.

I called the US Geologic Survey (USGS) office and told them about these radio events. I learned from them that ham operators in the area had also reported radio noises accompanying earthquakes, but no one had recorded them. Jack Everenden, with whom I was speaking, asked for copies of my data, which I sent.

Two weeks later, William Daily of Lawrence Livermore Labs called, asking if I would like to work with him gathering earthquake radio noise data under a grant from the USGS.

Radio Earth

For the next three years we deployed monitoring/recording devices along the San Andreas fault, from San Francisco to San Diego. The units were battery-powered paper-chart recorders which could hold one month's worth of data. They recorded radio noise levels in three adjacent bands: 0.2-1, 1-10 and 10-100 kHz. In addition we continued using the APM recorders in two locations, Sausalito and San Mateo.

During this period, some 46 earthquakes 4.0 and above occurred within 120 miles of our stations. Of these, 32 quakes were preceded by a radio anomaly. Only five quakes were not preceded by radio precursors. These were also ten false positives (radio events with no quakes following). These may have been caused by earthquake prepartion forces which failed to mature. Either way, our score was about 70%.

The results of our study were published in October 1989, just as the Loma Prieta Earthquake struck northern California.

By this time we had dismantled our network of recording stations. However, one of the original APM recorders was still running at my lab in Sausalito. This instrument recorded the largest radio depression I have ever seen, about 60 days prior to the October 17 shocks (Figure 3) [Not shown]. I had reported that event to Galilee Harbor's board of directors, but no action was taken.

In studying several smaller earthquakes from 1985-1987, it appeared that the larger the earthquake, the larger and sooner the precursors appeared. The 6.0 earthquake of April 24, 1984 was preceded by a radio depression 6 days before the shock. The Loma Prieta Earthquake of about 7.0 magnitude was preceded by a much greater radio depression 60 days before. A 7.0 magnitude quake is 10 times greater than a 6.0. The 60-day precursor time for the 7.0 earthquake was 10 times the precursor time for the 6.0 earthquake. More data is needed to clarify this relationship.

Warrick's lab showed that fracturing rocks generate radio waves: when Westerly granite was crushed in a shielded space, a receiving antenna detected broadband signals ranging from 500 kHz to 30 MHz. Most of the energy was concentrated at the lower frequencies.

Other experimenters measured changes in the electrical resistance of rocks under pressure. During the late 1970s, William Brace of MIT compressed various rocks in a powerful press while recording their resistance. He found that as rocks approach fracture pressure, they become much more electrically conductive. A related experiment by William Daily at Lawrence Livermore Lab subjected rocks to evenly distributed pressure while their electrical resistance was measured. Under uniform pressure, the rocks did not show the changes in resistance produced in Brace's press. That suggested it was stress caused by force being applied unevenly which caused the observed changes in resistivity.

Although Warwick's experiment proved rocks can emit radio waves during crushing, calculations showed that any such waves generated far underground would be absorbed by the earth, never reaching the surface with enough energy to be detected in the atmosphere. In addition, this effect could not explain the decrease of ambient radio energy observed by us and others.

Takeo Yoshino, of the University of Electro-Communications in Tokyo, has proposed that "resistance slots" form along a fault line due to effects similar to those demonstrated by Brace. Yoshino argues that if ground resistance becomes high enough in these slots, then radio waves coming from below will pass through them, rather than being absorbed, and enter the atmosphere. It would also mean atmospheric radio energy could pass into the earth through these slots. This could create interesting resonant effects.

Does ground resistance actually reach the levels needed to sustain such an effect? It is known that ground water enhances ground conductivity. However, C.B. Raleigh of the USGS has calculated that enough heat can be produced by friction during the earthquake preparation process to boil the ground water out of a rupture zone. Perhaps dehydration could combine with stress-induced fluctuations in rock resistance to produce slots of heightened electrical resistance in the earth's crust.

Based on this idea, it is my belief that the radio depressions and emissions recorded by us and others are the result of fluctuations in ground radio absorption.

Radio waves moving through the atmosphere are always being partly absorbed into the ground. The absorption rate varies from place to place, based on the ground's conductance and the distribution of rocks and sediments. If anything alters this equilibrium, the radio fields in the atmosphere should also be affected. For instance, more ground absorption should result in a lower intensity in the atmosphere. A loss of absorption would produce increased intensity in the atmosphere. Seismic radio events may be due to this effect.

As a model for explaining the observed radio anomalies, this has appeal, since it can account for both radio emissions and depressions. It could also explain the changes in telluric currents recorded in Greece prior to earthquakes. As ground conductance changes, currents flowing through the Earth may be diverted to channels and zones of greater conductance.

As more data is gathered, we'll understand more about these phenomena. In the meantime, though, we're on a slow learning curve, limited by the frequency of large earthquakes. There is really no way to speed up this process, and perhaps we don't actually want to.


Brady, B.T. & Rowell, G.A.: "Laboratory investigation of the electrodynamics of rock fracture", Nature (London) 321: 29, may 1986.

Dazey, M.H. & Koons, H.C.: "Characteristics of a power line used as a VLF antenna", Radio Science 17(3): 589-597 (1982).

Dmowska, R.: "Electromagnetic phenomena associated with earthquakes", Geophys. Serv. 3: 157-174 (1977).

Fraser-Smith, A.C, et al.: "Low-frequency magnetic field measurements near the epicenter of the Ms 7.1 Loma Prieta earthquake", Geophysical Research Letters (submitted 1990).

Gokhberg, M., et al.: "Experimental measurements of electromagnetic emissions possibly related to earthquakes in Japan", J. of Geophys. Res. 87(B9): 7824-7828 (1982).

Gokhberg, M., et al.: "Seismic precursors in the ionosphere", Izvestia Earth Physics 19: 762-765 (1983).

Gokhberg, M., et al.: "Resonant phenomena accompanying seismic-ionospheric interaction", Izvestia Earth Physics 21(6), 1985.

Nitsan, U.: "Eletromagnetic emission accompanying fracture of quartz-bearing rocks", Geophys. Res. 4: 333 (1977).

Parrot, M. & Lefeuvre, F.: "Correlation between GEOS VLF emissions and earthquakes", Annales Geophysicae 3: 737-748 (1985).

Remizov, L., & Oleynikova, I.: "Spectral characteristics of the natural random Earth's field in the frequency band from a few hertz to 50 kHz", UDC 525.2.047: 621.391.244.029.4 (1984).

Sadovsky, M., et al.: "Variations of natural radiowave emission of the Earth during severe earthquake in the Carpathians", Dokl. Akad. Nauk. SSR 244(2): 316-319 (1984).

Tate, J. & Daily, W.: "Evidence of electro-seismic phenomena", Physics of the Earth & Planetary Interiors 57: 1-10 (1989).

Tate, J: "Radio absorption and electrical conductance in the earth's crust" (1990, publication pending).

Vorotsos, P. & Alexopoulos, K.: "Physical properties of the variations of the electric field of the earth preceding earthquakes", I. Tectonophysics 110: 73-98 (1984).

Warwick, J., et al.: "Radio emissions associated with rock fracture", J. Geophys. Res. 87(84): 2851-2859 (1982).

US Patent  # 4,628,299

Seismic Warning System Using RF Energy Monitor

Joe Tate, et al.

Abstract -- The ambient broadband radio frequency field strength from broadcast stations is monitored (Figure 4) by periodic sampling (50, 52). A warning indication is provided if the field strength drops significantly. Drops in such field strength have been correlated empirically with the occurrence of seismic activity, usually several days later. Thus the indication serves as an early warning of an impending earthquake. In one preferred embodiment, a broadband, horizontal, very long monopole antenna (40) was connected to a rectifying and smoothing circuit (Figure 3) to provide a dc output proportional to the ambient rf field. This voltage is digitized (50), and using a suitably programmed computer (52), the digital version of the field strength signal is sampled once per minute (78). A cumulative or running average of the minute samples is calculated (80) and held. Once per hour the latest running average is stored (84) and a standard deviation (SD) of the last 24 hourly stored running averages is calculated (88). If the SD exceeds a predetermined value, 0.3 in one embodiment, an alarm is triggered (92). The use of the SD eliminates the effect of day-to-day changes in the amounts of the variations of the ambient field strength, due to changes in tides and other factors. Once per day the samples are written (96) to a permanent storage file and a continuous plot of the field strength is also made (14). Preferably the alarm is triggered only if another detector also provides an indication (FIG. 6), thereby to eliminate the effect of machine error.

Inventors:  Tate; Joseph B. (Sausalito, CA); Brown; David E. (Mill Valley, CA)
Assignee:  Pressman; David (San Francisco, CA)
Appl. No.:  695632; Filed:  January 28, 1985
Current U.S. Class: 340/540; 324/323; 324/344; 340/600; 340/690; Intern'l Class:  G08B 021/00
Field of Search:  340/540,600,690

References Cited
U.S. Patent Documents

4,214,238, Jul., 1980, Adams et al. 340/540.
4,364,033, Dec., 1982, Tsay 340/540.


Background: Field of Invention

This invention relates to the prediction of the fugure occurrence of seismic activity, particularly to the advance notification of earthquakes through the monitoring of ambient radio frequency (rf) energy.

Background: Description of Prior Art

Heretofore, insofar as we are aware, seismology, the science of earthquakes, has not been able to make any near-term predictions of earthquakes.

While scientists have known that certain animals may have had some sort of advance knowledge of quakes, due to the fact that they exhibited peculiar behavior before quakes, and not at other times, this behavior has not been consistent and reliable enough to be of practical use.

Also, while scientists have also been able to predict thunderstorms in advance by monitoring the ambient electrostatic field (see, e.g., US Pat. No. 3,611,365 to Husbyorg and Scuka, 1968; 3,790,884 to Kohl, 1974; and 4,095,221 to Slocum, 1978), they have not been aware of any corresponding system for earthquake prediction.

Scientists have been able actually to detect earthquakes during their occurrence by monitoring air pressure variations (e.g., as described in US. Pat. No. 4,126,203 to Miller, 1978) and by monitoring the earth's physical movement by seismographs but, again, science has not been aware of any system for short-term advance detection or prediction of quakes.

Due to the devastating effects of quakes to property, life, and limb, public and governmental authorities would derive great benefit from any system which could provide short-time advance notification of great earthquakes. As it is now, except for aftershocks, which seismologists know will occur after any large quake, all great and small quakes occur without warning. Because people in the vicinity of such quakes are unprepared, they often are in places of great vulnerability, such as beside or inside collapsible buildings, so that severe and human injury usually occurs during a quake. Also, property itself is left vulnerable, e.g., by leaving automobiles in or near collapsible buildings, leaving gas and electricity connected such that disruption of these facilities causes fires, and leaving other valuable property in vulnerable areas. If advance notification of a large quake could be provided to the public and civil authorities, people and valuable property could be evacuated and protected, thereby preventing deaths, injuries, and greatly reducing property damage. Further, advance notification of quakes would eliminate the severe psychological trauma which often affects large segments of the populace due to the surprise occurrence of quakes.

Objects & Advantages

Accordingly several objects and advantages of the invention are to provide a reliable and effective method of earthquake prediction, to provide a method of preventing death, injuries, and reducing property damage in earthquakes, and to provide a method of reducing the psychological trauma which often accompanies quakes due to their surprise occurrence. Additional objects are to provide such a system which is easy to use, economical, reliable, and portable. Further objects will become apparent from a consideration of the ensuing description, taken in conjunction with the accompanying drawings.

Background: Theory of Invention

The following is a discussion of the background theory of the invention. While we believe it to be technically accurate, we do not wish to be limited by this theory since the operability of the invention has been empirically verified, as will be apparent from the later discussion.

We have recently worked work with the reception and utilization of broadband radio-frequency reception, e.g., for low-power utilization applications, as discussed in the copending application Ser. No. 06/539,223 of Joseph B. Tate, filed Oct. 6, 1983. While doing this work, we have noted that the antenna's output voltage fluctuated with time due to certain, known causes.

First, we noted that the higher we placed an antenna above the ground, the the greater the output signal it provided. We have observed this by raising the physical height of an antenna and observing an increase in power output, and also by observing variations in the output of a fixed antenna near a body of ocean water as a function of the tides: the antenna's output was greatest at low tide and lowest at high tide. We believe that the change in water level, which serves as a ground plane, effectively lowers or raises the height of the antenna above the ground.

We also noted that the antenna's output was affected by solar flares to a limited extent; these caused the antenna to produce a higher output voltage during their occurrence. We believe this phenomena is caused by an increase in the level of ambient ionization due to the flares.

Further, we noted that the antenna's output dropped at certain irregular times; at first we would not attribute any cause to these drops. However investigation enabled us to correlate these drops with the subsequent occurrence of seismic activity. We found that the magnitude of the drop was proportional to the size of the subsequent earthquake.

Certain phenomena have been discovered to precede earthquakes. These include an anomalous uplift of the ground, changes in the electrical conductivity of rock, changes in the isotopic composition of deep well water, changes in the nature of small earthquake activity (e.g., bunching of small foreshocks), anomalous ground tilt or strain changes, changes in physical properties, such as porosity, electrical conductivity, and elastic velocity in the hypocentral region. Earthquake, McGraw-Hill Encyclopedia of Science And Technology, 1960; Earth by F. Press, W. H. Freeman & Co., 1974.

Phenomena associated with rocks have attracted much recent attention. Wm. Brace of the Mass. Inst. of Technology has found that when rocks were squeezed or compressed, just before they fractured, they tended to develop hairline cracks, swell or dilate (dilatancy), become more porous and electrically conductive, and transmitted high frequency seismic-like waves more slowly. Two of Brace's former students, Amos Nur of Stanford University and Christopher Scholz of Lamont-Doherty furthered Brace's work, connecting the dilatancy theory with seismic P-wave velocity shifts and rock resistivity changes as a precursor for earthquakes. See. e.g., Brace, Orange, and Madden, J. Geophys. Res., 70(22), 5669, 1965; A. Nur, Bull. Seis. Soc. of Amer., V 62, Nr. 5, pp. 1217-1222, 1972 Oct.; Earthquake by B. Walker, Time-Life Books, 1982.

Based upon the above background, we have developed a theory as to the cause of this drop in antenna output as a precursor or predictor of earthquakes. We believe that before a quake occurs, the pressure within underground rock bodies temporarily increases greatly, causing the rocks to dilate and become conductive, in accordance with the works of Brace, Nur, and Scholz. This increase in conductivity effectively raises the ground plane, thereby causing the antenna's output to decrease temporarily.

Thus before the occurrence of a quake, the underground pressure increases greatly temporarily, causing underground rock bodies to swell and become more conductive, thereby raising the ground plane, which in turn causes the voltaic output of nearby antennas to drop.

We accordingly constructed an apparatus to automatically monitor antenna output and provide a suitable indication if the output level dropped significantly. The indication was calibrated empirically after much experimentation so as to filter out the effects of solar- and tide-caused variations. We did this by arranging the apparatus so that an output indication was provided only if the antenna output dropped a predetermined degree beyond its average level; we utilized statistical filtering techniques to accomplish this.


Figure 1 shows the front panel of a Seismic Early Warning (SEW) apparatus according to the invention.

Figure 2 is a plot of voltage (representing ambient rf level) v. time as measured by the apparatus of Figure 1.

Figure 3 is a schematic diagram of an ambient power module circuit (used in the SEW apparatus) for producing a DC output voltage proportional to the ambient rf energy

Figure 4 is a block diagram of a computer in the apparatus of Figure 1.

Figure 5 is a flowchart which depicts the operation of the SEW system.

Figure 6 is a flowchart which depicts the operation of an optional alarm trigger system useable with the SEW apparatus.

Figure 1: Seismic Early Warning Apparatus

In accordance with the invention, a seismic early warning apparatus is provided as shown in FIG. 1. The apparatus consists of a housing containing a general purpose computer (not shown), a disc drive 10, an analog system comprising a microampere meter 12 arranged to monitor direct current (which is proportional to the ambient rf energy), and a direct current strip chart recorder 14 arranged to provide a continuous indication of the current antenna output, which will be called the ambient power level. A hexidecimal keypad 16 is provided to enter data, such as time, for entering programs and changes and for operating the system according to preset codes. The time, date, and voltaic level of the antenna's output are continuously indicated by digital readouts 18, 20, and 22, respectively. A screen display 24 is provided to display graphic and alphanumeric information of the current status of the apparatus and previous data records.

Lastly the apparatus includes four status-indicating lamps, which preferably are LEDs (light-emitting diodes) as follows: A green LED 26 indicates that the system is on and functioning normally. A yellow LED 28 indicates that the system has detected an event, namely the occurrence of a drop in ambient power below the preset level, which would be the prediction of an impending earthquake. A red LED 30 is provided as backup confirmation of the occurrence of the event; LED 30 is illuminated when a duplicate receiving system also detects an event. A blue LED 32 indicates initiation of operation of an automatic telephone dialer within the system, which has been preprogrammed to dial a predetermined number and provide a warning in the event of an occurrence of an alarm condition. Lastly the apparatus includes a hard copy output port 33 for providing printed graphic and numeric outputs of all system data.

Figure 2: Ambient RF Level vs Time Before Quake

Figure 2 illustrates a reproduction of an actual plot of a voltage as a function of time, which voltage was proportional to the ambient RF (radio frequency) level, from the period from before to after a relatively large earthquake. This plot, which is typical of many we have observed before a quake, was made by deriving the voltage with a 30-meter, long-wire monopole antenna (not shown) which was mounted horizontally and which extended over San Francisco (Richardson) Bay easterly from Sausalito, California, 9 meters above sea level. The antenna thus intercepted and converted to an RF voltage the ambient RF energy, mainly from local (San Francisco area) AM radio stations. We rectified and filtered the output of the antenna using one-half of the circuit of FIG. 3 (described below) to provide a DC voltage which was plotted on a conventional ink-on-paper plotter. Note that on the section of the chart for Apr. 19 (1984), which begins at time 0:00 (midnight) and ends at 24:00, the voltage or ambient RF power level at the antenna increased and fell and then increased slightly in the 24-hour period. This wavelike variation typically occurs on a daily basis and is caused by tides: the peaks occurring at low tide when the effective ground plane provided by the water drops and the troughs occurring at high tide when the ground plane rises.

On Apr. 20, from about 8:00 to about 12:00, a sharp and constant-level dip in the ambient rf power occurred, as indicated. The magnitude of this pronounced dip is far greater than the normal tide-caused variations, as is its beginning and ending slope.

Thereafter, from Apr. 20 to Apr. 23, the plot (not shown) continued unremarkably, albeit with a slight variation from normal.

The same occurred on Apr. 24, with the plot actually being generally similar to a normal day. However at 13:15 on Apr. 24, as indicated, a large, Richter magnitude 6.0 quake occurred near Hollister, Calif., about 340 km away from the antenna. No change in the plot occurred at this time.

Correlation of this quake with the plot's marked dip of Apr. 20 was made by the repeated observation of dozens of similar dips and subsequent quakes. Pronounced dips were always followed by a quake several days later. Thus we have empirically established causal and theoretical connections between pronounced dips of the type shown and the occurrence of subsequent seismic activity.

Figure 3: Ambient Power Module

The circuit of Figure 3 is used to convert the ambient RF energy to a direct voltage which can be used and handled by data processing equipment. Designated an ambient power module (APM), it is connected to an antenna 40, preferably a broadband monopole antenna of the type described in the preceeding section. The distal end of the antenna is free and its proximal end is connected to the circuit via two capacitors Cp1 and Cn1, each being in series with the signal line for coupling and each having a value of 0.047 microfarad. Taking the left or negative side of the circuit first, it comprises two rectifiers (diodes) Dn1 and Dn2 (1N34 type) and a filter capacitor Cn2 (40 microfarads). Rectifier Dn1 is connected in parallel to the signal path and rectifier Dn2 is connected in series, in the well known voltage multiplier arrangement. Capacitor Cn2 is connected in parallel across the output of the APM to smooth the rectified output. The right or positive side of the circuit is similar, except for the polarity of the diodes.

In operation, an RF voltage is developed across antenna 40; this voltage is voltage multiplied by the two rectifiers on each side of the circuit. The resultant direct voltages are smoothed or filtered by capacitors Cn1 and Cp2 and are supplied to output terminals 42 and 44. A positive version of this direct voltage is plotted in Figure 2, as described above.

Figure 4: Block Diagram of Computer

A computer for performing the monitoring and alarm functions of the invention and which is provided within the apparatus of Figure 1 is shown in Figure 4. The computer receives the positive voltage from the APM (Figure 3) and processes this, providing an alarm if the voltage dips a predetermined amount from its recent average value.
The computer comprises an analog to digital converter (ADC) 50 which is arranged to convert the positive DC voltage from the AAPM to digital form, preferably in the form of a parallel signal at the output of ADC 50. The digitized voltage from ADC 50 is supplied to a central processing unit 52, which is a type 68000 microprocessor or computer on a chip. CPU 52 and ADC 50 are clocked by a clock 54 in conventional fashion.

CPU 52 operates on instructions from a program contained in an electrically programmed read only memory (EPROM), the program being listed later. CPU 52 temporarily stores data in a read and write memory (RAM) 58. CPU 52 also supplies output data to display screen 24, disc drive 10, and hard-copy printer 26', each of which was already described in conjunction with Figure 1.

CPU 52 can receive input data manually from hexidecimal keypad 16 (see FIG. 1) via a keyboard encoder 60.
CPU 52 can supply an alarm output to a radio transmitter or automatic telephone dialer 62 via a modem (modulator-demodulator) 64 for connecting the CPU to a phone (not shown).

As also indicated in Figure 4, the negative output of the AAPM of Figure 3 is connected to ammeter 12 and chart recorder 14.

Figure 5: Flowchart of Seismic Early Warning System

In operation, the system of Figure 4 operates under control of the program in EPROM 56 in accordance with the flowchart of Figure 5 as follows:

Startup: Blocks 70 and 72: An initialization and start-up sequence is first initiated when the machine is turned on, as indicated by block 70; this sets all registers and counters to zero. The time and data are then set manually (using EPROM 56), as indicated by block 72.

Clock Reading: Blocks 74 and 76: Next, under automatic program control, the machine reads the elapsed time on its clock display register, as indicated by block 74. If the "seconds" register does not indicate the number one (#1), the machine continues to read the clock, as indicated by the "no" output of decision block 76.

Minute Sample: Block 78: When second #1 appears, as it will once per minute, the decision in block 76 will be "yes", so that the machine will take one sample of the rectified, smoothed, and digitized version of the antenna's output, i.e., the output of ADC 50 of Figure 4, as indicated in block 78. This sample will be taken once per minute, i.e., whenever second #1 is displayed.

Running Average: Block 80: Next, as indicated by block 80, a running average of the samples taken in block 78 is calculated. This is done by accumulating the samples to keep a running total of their values, counting the number of samples accumulated, and dividing the running total by the latest number of samples each time a new sample is taken.

Store Hourly Average: Blocks 82 and 84: Next, as indicated in block 82, a test is made to see if the time display register indicates that minute number one (#1) has come up. If not, the decision is "no" and the clock is read again (block 74). If the decision is "yes", as it will be once per hour, the running average in the accumulator will be stored (block 84) and the accumulator will be cleared or reset to zero.

One Day Test: Block 86 ("No" decision) and Block 94: Next the machine makes a test to see if 24 hours have passed. If not, the machine will not be able to make any valid statistical determinations. Thus it must run at least 24 hours before being operative. Assuming the decision in block 86 is negative (24 hours have not yet elapsed) another test is made (block 94) to see if hour zero is indicated, which will occur once per day. If hour zero is not indicated, (decision in block 94 is negative), the clock will be read again (block 74) in the usual loop.

Calculate SD: Block 86 ("Yes") and Block 88: If a full day has elapsed, so that valid statistics can be calculated ("yes" from block 86), the standard deviation (SD) of the last 24 hourly averages is calculated, as indicated in block 88. This is done once per hour. The calculation is made using the usual SD formula

SDDEV=SQR([sum(x-X).sup.2 ]/n)

where SDDEV=SD; SQR=the square root; sum=the sum of; x=the individual hourly averages; X=the mean of the hourly averages; and n=the number of individual hourly averages. Essentially the SD is calculated by taking the mean of all of the hourly averages, taking the difference or deviation of each hourly average from the mean, squaring each deviation, taking the mean of the squared deviations, and then taking the square root of the mean of the squared deviations.

Evaluate SD: Block 90: The SD is then evaluated to see if it is greater than 0.3. This value has been empirically determined to be the level at which the present apparatus will provide a reasonably positive indication that an earthquake will occur, while neglecting the effects of non-seismic-caused variations. If the SD is less than 0.3, (a "no" output from block 90), this indicates that the last hourly average was not greatly different from the average of the last 24 hourly samples, so that no alarm need be indicated. I.e., the antenna's output did not drop significantly to indicate an impending earthquake. Thereupon the program moves to block 94, where a test is made for the existence of hour zero, as described. If, however the SD exceeds 0.3 ("yes" output of block 90), this indicates that the antenna's output has dropped significantly so as to affect the last hourly average, thereby to indicate an impending earthquake.

Alarm: Block 92: In response to the Yes output of block 92, an alarm is triggered (block 94). The alarm may be a bell, the dialing of a telephone to a location where personnel are present if the apparatus is placed at a remote or non-manned location, or the initiation of the further program of the Flowchart of Figure 6, the alarm trigger sequence. To eliminate the possibility of equipment failure and to provide confirmation from another apparatus at another location, we prefer to provide an alarm only upon confirmation from another apparatus, as discussed in the description of Figure 6 below.

Make Record: Block 94 ("Yes") and Block 96: If hour zero is being displayed when the operation of block 94 is performed, which occurs once per day at midnight, the operation of block 96 will be performed, i.e., the data in the registers will be stored to disc to create a permanent record and the registers will be cleared to create new data for the next day. However the previous 24 hourly averages are still stored at all times so that a valid SD can be calculated and tested every hour. After the operation of block 96, the clock is read again in accordance with the regular program (block 74).

Figure 6: Alarm Trigger Flowchart

The sequence of Figure 6 is performed when the alarm is triggered in block 92 of Figure 5 as an optional, but preferred backup confirmation of an impending earthquake. The operations in the backup confirmation system will be described briefly.

Beginning with blocks 100 and 102, the system is continually tested (hourly) for the occurrence of a SD of the hourly averages of greater than 0.3. If the SD is greater than 0.3, the alert indicator (28 of Figure 1) is triggered (block 104) and the program initiates a test (block 106) to see if a backup apparatus (not shown) is present. If so (yes output of block 106) the backup apparatus is also checked (blocks 108 and 110). If the backup does not indicate an excess SD, the indicators are reset to normal (block 112), but if backup confirmation is received, the alarm indicator (30 of Figure 1) is triggered per block 114 and a preprogrammed telephone number is dialed and indicator 32 is lit (block 116).

After the alarm condition is manually checked and the system is reset, the output of block 120 will be a "yes" and the system will be reset to normal (block 112). If a valid alarm condition is indicated and confirmed, civil authorities will have time (usually several days) to notify the populace, evacuate the area, or take any other needed precautions, depending on the size of the impending quake as indicated by the size of the standard deviation.


The attached computer programs will perform the calculations and operations above described. These programs are written in the BASIC programming language. Program "RECVOLT.AL" runs continuously and writes the information to disc every 24 hours. Program "GRASTAT.*" is manually run; it reads data from the disc and plots it on the screen or printer, as desired.

While the above description contains many specifications, these should not be construed as limitations on the scope of the invention, but merely as an exemplification of one preferred embodiment thereof. Many other variations are possible. For example, the programming language can be changed, or the calculations and operations can be performed with hard-wired conventional circuitry in lieu of a programmed computer. More than two corroboration receivers can be used, and these can be placed at various locations. In lieu of testing the antenna's output reception of the area's AM stations, a special, dedicated transmitter with a special, dedicated frequency and a specially-tuned matching receiver can be used to avoid dependence on stations which are not under the control of the earthquake prediction system and its personnel. The transmitter and the receiver should be spaced apart geographically, preferably by at least several km, so that the ground plane conduction phenemonon can operate. Also the transmitted signal can be a specially-coded or modulated signal, or it can be an auxiliary signal of a regular transmitter, e.g., a SSB or SCA signal, together with a matching receiver. In lieu of a test for an excess SD, the apparatus can be arranged to test for a predetermined drop in the value of the antenna output from its immediately previous value or its average value over a predetermined period, such as an hour or day, or for a drop having greater than a predetermined slope. Accordingly the full scope of the invention should be determined by the appended claims and their legal equivalents, and not by the examples given.

Claims -- [ Not included here ]