Parts List for the APM-2
Four 1N34 germanium diodes (Radio shack #276-1123) ~ Figure 1, X1,
X3, & X4
Two 0.2 mfd 50 V ceramic capacitors ~ Figure 1, C1 & C2
Two 100 mfd 50V electrolytic capacitors (Radio Shack #272-1016) ~
1, C3 & C4
Copper wire for antenna & ground connections
The Ambient Power Module (APM) is a simple electronic circuit
when connected to antenna and earth ground, will deliver low voltage up
to several milliwatts. The amount of voltage and power will be
by local radio noise levels and antenna dimensions
Generally a long wire antenna about 100' long and elevated in a
position about 30' above ground works best. A longer antenna may be
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
The actual circuit consists of two oppositely polarized voltage
(Figure 1). The DC output of each doubler is connected in series with
other to maximize voltage without using transformers. Single voltage
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
below 1 MHz. The basic circuit may be combined with a variety of
regulation schemes, some of which are shown in Figure 2. Using the
to charge small NiCad batteries provides effective voltage regulation
well as convenient electrical storage. This is accomplished by
the APM-2 as shown in Figure 2B.
Charging lead acid batteries is not practical because their
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
very high radio noise.
It can be used to power small electronic devices with CMOS
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
loads from 0-19 kOhm. This unit was operating from a 100' horizontal
about 25' high in Sausalito CA. As can be seen from the plot, power
rapidly as the load resistance decrease from 2 kOhm. This means that
voltage, high impedance devices, like digital clocks, calculators and
alarms are the most likely applications for this power source. Some
are shown in Figures 4 through 7.
Figure 4 ~ A digital clock is shown powered by the APM-2. The 1.5
clock draws 28 microamps. Its position on the power envelope curve
be off the scale to the right and almost on the bottom line,
only 42 microwatts.
Figure 6 shows a clock which has the APM-2 built into it so it is
necessary to connect the antenna and ground wires directly to the
The antenna for this clock, which is a low frequency marine type, is
in Figure 7.These antenna are expensive, not generally available, and
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
Building the Module
The builder has a choice of wiring techniques which may be used to
the module. It may be hand wired onto a terminal strip, laid out on a
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
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
up on a solder strip terminal.
If you wish to make only one or two units, hand wiring will be
practical, either on a terminal strip or breadboard. Assembly on the
strip (Figure 8A) can be done easily and without soldering. It is
to get the polarity correct on the electrolytic capacitor. The arrow
on the side of the capacitor points to negative.
Figure 9 is a closer view of the terminal strip with an
of the components and how they are connected.
The breadboard unit is shown in Figure 10 with all components on
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
on the other side. Just follow the pattern in the photo, making sure to
observe the correct polarity on the electrolytic capacitors and the
The ceramic capacitors may be inserted in either direction.
The experiment board unit is assembled by simply pushing the
leads into the board as shown in Figure 11. This unit is powering a
red LED indicated by the arrow.
The solder strip unit is made up on a five terminal strip. The
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
Clip a heat sink onto the lead between the diode and the terminal as
in Figure 12.
It is beyond the scope of this pamphlet to show how to make
circuits, but the layout of the board is provided in Figure 13.
Figure 14 shows the front and back view of the completed printed
A small switch may be installed on the board to activate the zener
(Figure 15). This board was designed for use in clocks.
The antenna needs to be of sufficient size to supply the APM with
RF current to cause conduction in the germanium diodes and charge the
coupling capacitors. It has been found that a long horizontal wire
best. It will work better when raised higher. Usually 20-30 feet is
Lower elevations will work, but a longer wire may be necessary.
In most location, possible supporting structures already exist.
wire may be stretched between the top of a building and some nearby
or telephone pole. If live wires are present on the building or pole,
should be taken to keep your antenna and body well clear of these
To mount the wire, standard commercial insulators may be sued as
as homemade devices. Plastic pipe makes an excellent antenna insulator.
Synthetic rope also works very well, and has the advantage of being
simply by tying a knot. It is convenient to mount a pulley at some
point so the antenna wire may be pulled up to it using the rope which
as an insulator (Figure 16).
Figure 17 is an illustration of a horizontal wire antenna using a
and tree for supports.
Usually a good ground can be established by connecting a wire to
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
steel rods are made for grounds which have the advantage of good
to copper wire. A ground of this type usually is found within the
system of most buildings.
Conduit is a convenient ground provided that the conduit is
grounded. This may be checked with an ohmmeter by testing continuity
the conduit and system ground (ground rod). Just as with the antenna,
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
Grounding in extremely dry ground can be enhanced by burying some
around the rod. The slats will increase the conductivity of the ground
and also help retain water. More information on this subject may be
in an antenna handbook.
Good luck getting your Ambient Power Module working. It is our
that experimenters will find new applications and improve the power
of the APM.
Science News [date unknown]
Radio Waves Signal
From the bright flashes reported to appear in the sky during
earthquakes to computer breakdowns during severe tremors, scientists
long suspected that seismic activity is associated with a variety of
effects. Recently researchers have been taking a careful look at this
with an eye toward using it to predict earthquakes.
One such study is being conducted by Joseph Tate of Ambient
in Sausalito, CA, and William Daily at Lawrence Livermore National
in Livermore, CA. With a system of radio wave monitors distributed
California's San Andreas fault, the researchers have recorded two kinds
of changes in atmospheric radio waves prior to earthquakes that
between 1983 and 1986.
The most common change is a drop in the radio signals that
pervade the air as a result of lightning and human sources such as car
ignition systems and electric power grids. This reduction typically
one to six days before an earthquake and can last for many hours. For
a magnitude 6.2 earthquake that shook Hollister CA in April 1984 was
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
the earthquake, the longer the time between the radio wave depression
Laboratory studies have shown that the electrical conductivity of
increases as they are stressed. Based on this and their electrical
of the ground, Tate and Daily think the increased conductivity of
rocks near the fault causes more radio waves to be absorbed by the
rather than their traveling through the air. They also plan to test a
link between radio wave drops and the emission of radon gas, which
is thought to be a quake precursor. The radon may ionize the air,
it temporarily more absorptive than the detector antenna.
The researchers have also found, in addition to these drops,
prequake phenomenon in which short pulses of increased radio wave
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
laboratory work showing that cracking rocks release electromagnetic
Tate says that in their first attempts at predicting earthquakes
1984 and 1985, they did not miss a single event, so he his optimistic
using this technique for short-term forecasting of San Andreas quakes.
"In three to five years", he says, "we should be able to issue
Whole Earth Review (Fall 1990, pp. 101-104)
Radio Earth: The
Since the earliest days of radio research, many people have
of these invisible waves as artificial, an effect created solely by
in a laboratory. Later, in the 1930s, Karl Jansky discovered radio
coming from the Milky Way. Stars are now known to be giant
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
caused by lightning was known to have recognizable propagation
It was these patterns that Jansky was measuring when he discovered
Tesla actually calculated the resonant frequency of the Earth, and
that electromagnetic waves of this frequency (6-8 Hz) should be
by the planet from the action of lightning. These "Schumann
as they came to be known, were finally detected in the 1960s.
Other strange radio emissions were noticed at about the same time,
time when many new radio observatories were starting operation at
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
received at six widely scattered radiotelescopes. The connection
these radio signals and the earthquake was eventually shown by James
of the University of Colorado, who analyzed the observatories'
recorded data (Figure 1) [Not shown]. Earthquakes generate radio waves!
Twenty-two years later, after performing a series of laboratory
in which rocks were crushed in powerful presses and the resulting
emissions were measured, Warwick's paper describing the phenomenon
in the April 1982 issue of the Journal of Geophysical Research.
In the meantime, other experimenters had recorded similar effects
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.
Greece, researchers found that telluric currents (natural currents of
flowing in the Earth) fluctuated prior to earthquakes.
In 1979, I was experimenting with methods of turning radio energy
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
radio, except that it did not have a tuning circuit. Because of this,
Crystal Clock (as I called it) was able to absorb a wide spectrum of
noise from the antenna and yield electric power. The power supply was
to deliver much more current than was developed in a crystal radio,
its output was still just a few millivolts.
In the early 80s I demonstrated the clock to the late Frank
then director of San Francisco's Exploratorium, where I worked in the
repair shop. Oppenheimer suggested recording the power supply's output
over a long period of time to determine its dependability. After all,
device relied completely on whatever stray signals happened to be in
Using an Atari computer which had been donated to themuseum, the
of the clock's power supply was measured continuously and recorded on
disk. This was done by feeding the unregulated voltage output direcly
the coputer's joystick port.
I began calling this power supply the "Ambient Power Module" (APM)
it extracted power from ambient background radio noise. This small
when connected to antenna and ground, used the potential difference
air and ground to generate a small direct current continuously.
As we studied the recorded data, mild fluctuations were noted in a
cycle. The patterns were consistent over long periods of time, though
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
from the APM recording station in Sausalito. Days later, while looking
through the data, I noticed that the APM output dropped to less than
its normal value for several hours during the afternoon 6 days before
earthquake (Figure 2) [Not shown] this was very peculiar, because most
of the APM's power came from broadcast signals, and broadcasting
hadn't done anything different that afternoon. Apparently something had
temporarily depressed the propagation of radio waves. At high
such effects can be caused by atmospheric conditions. But the lower
involved here are hardly affected, particularly not the signals from
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
Perhaps these also were preceded by similar radio anomalies. Looking
through the accumulated data on the APM's power output, indeed,
less obvious radio depressions were found to occur prior to the lesser
I called the US Geologic Survey (USGS) office and told them about
radio events. I learned from them that ham operators in the area had
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,
if I would like to work with him gathering earthquake radio noise data
under a grant from the USGS.
For the next three years we deployed monitoring/recording devices
the San Andreas fault, from San Francisco to San Diego. The units were
battery-powered paper-chart recorders which could hold one month's
of data. They recorded radio noise levels in three adjacent bands:
1-10 and 10-100 kHz. In addition we continued using the APM recorders
two locations, Sausalito and San Mateo.
During this period, some 46 earthquakes 4.0 and above occurred
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
Loma Prieta Earthquake struck northern California.
By this time we had dismantled our network of recording stations.
one of the original APM recorders was still running at my lab in
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
that the larger the earthquake, the larger and sooner the precursors
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
was preceded by a much greater radio depression 60 days before. A 7.0
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:
Westerly granite was crushed in a shielded space, a receiving antenna
broadband signals ranging from 500 kHz to 30 MHz. Most of the energy
concentrated at the lower frequencies.
Other experimenters measured changes in the electrical resistance
rocks under pressure. During the late 1970s, William Brace of MIT
various rocks in a powerful press while recording their resistance. He
found that as rocks approach fracture pressure, they become much more
conductive. A related experiment by William Daily at Lawrence Livermore
Lab subjected rocks to evenly distributed pressure while their
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
changes in resistivity.
Although Warwick's experiment proved rocks can emit radio waves
crushing, calculations showed that any such waves generated far
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
Takeo Yoshino, of the University of Electro-Communications in
has proposed that "resistance slots" form along a fault line due to
similar to those demonstrated by Brace. Yoshino argues that if ground
becomes high enough in these slots, then radio waves coming from below
will pass through them, rather than being absorbed, and enter the
It would also mean atmospheric radio energy could pass into the earth
these slots. This could create interesting resonant effects.
Does ground resistance actually reach the levels needed to sustain
an effect? It is known that ground water enhances ground conductivity.
However, C.B. Raleigh of the USGS has calculated that enough heat can
produced by friction during the earthquake preparation process to boil
the ground water out of a rupture zone. Perhaps dehydration could
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
recorded by us and others are the result of fluctuations in ground
Radio waves moving through the atmosphere are always being partly
into the ground. The absorption rate varies from place to place, based
on the ground's conductance and the distribution of rocks and
If anything alters this equilibrium, the radio fields in the atmosphere
should also be affected. For instance, more ground absorption should
in a lower intensity in the atmosphere. A loss of absorption would
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
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
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
of rock fracture", Nature (London) 321: 29, may 1986.
Dazey, M.H. & Koons, H.C.: "Characteristics of a power line
as a VLF antenna", Radio Science 17(3): 589-597 (1982).
Dmowska, R.: "Electromagnetic phenomena associated with
Serv. 3: 157-174 (1977).
Fraser-Smith, A.C, et al.: "Low-frequency magnetic field
near the epicenter of the Ms 7.1 Loma Prieta earthquake", Geophysical
Research Letters (submitted 1990).
Gokhberg, M., et al.: "Experimental measurements of
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
interaction", Izvestia Earth Physics 21(6), 1985.
Nitsan, U.: "Eletromagnetic emission accompanying fracture of
rocks", Geophys. Res. 4: 333 (1977).
Parrot, M. & Lefeuvre, F.: "Correlation between GEOS VLF
and earthquakes", Annales Geophysicae 3: 737-748 (1985).
Remizov, L., & Oleynikova, I.: "Spectral characteristics of
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
Earth during severe earthquake in the Carpathians", Dokl. Akad.
SSR 244(2): 316-319 (1984).
Tate, J. & Daily, W.: "Evidence of electro-seismic phenomena",
of the Earth & Planetary Interiors 57: 1-10 (1989).
Tate, J: "Radio absorption and electrical conductance in the
crust" (1990, publication pending).
Vorotsos, P. & Alexopoulos, K.: "Physical properties of the
of the electric field of the earth preceding earthquakes", I.
110: 73-98 (1984).
Warwick, J., et al.: "Radio emissions associated with rock
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
from broadcast stations is monitored (Figure 4) by periodic sampling
52). A warning indication is provided if the field strength drops
Drops in such field strength have been correlated empirically with the
occurrence of seismic activity, usually several days later. Thus the
serves as an early warning of an impending earthquake. In one preferred
embodiment, a broadband, horizontal, very long monopole antenna (40)
connected to a rectifying and smoothing circuit (Figure 3) to provide a
dc output proportional to the ambient rf field. This voltage is
(50), and using a suitably programmed computer (52), the digital
of the field strength signal is sampled once per minute (78). A
or running average of the minute samples is calculated (80) and held.
per hour the latest running average is stored (84) and a standard
(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
is triggered (92). The use of the SD eliminates the effect of
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
strength is also made (14). Preferably the alarm is triggered only if
detector also provides an indication (FIG. 6), thereby to eliminate the
effect of machine error.
Inventors: Tate; Joseph B. (Sausalito, CA); Brown; David E.
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;
Class: G08B 021/00
Field of Search: 340/540,600,690
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
seismic activity, particularly to the advance notification of
through the monitoring of ambient radio frequency (rf) energy.
Background: Description of Prior Art
Heretofore, insofar as we are aware, seismology, the science of
has not been able to make any near-term predictions of earthquakes.
While scientists have known that certain animals may have had some
of advance knowledge of quakes, due to the fact that they exhibited
behavior before quakes, and not at other times, this behavior has not
consistent and reliable enough to be of practical use.
Also, while scientists have also been able to predict
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,
and 4,095,221 to Slocum, 1978), they have not been aware of any
system for earthquake prediction.
Scientists have been able actually to detect earthquakes during
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
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
public and governmental authorities would derive great benefit from any
system which could provide short-time advance notification of great
As it is now, except for aftershocks, which seismologists know will
after any large quake, all great and small quakes occur without
Because people in the vicinity of such quakes are unprepared, they
are in places of great vulnerability, such as beside or inside
buildings, so that severe and human injury usually occurs during a
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
valuable property in vulnerable areas. If advance notification of a
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,
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
a reliable and effective method of earthquake prediction, to provide a
method of preventing death, injuries, and reducing property damage in
and to provide a method of reducing the psychological trauma which
accompanies quakes due to their surprise occurrence. Additional objects
are to provide such a system which is easy to use, economical,
and portable. Further objects will become apparent from a consideration
of the ensuing description, taken in conjunction with the accompanying
Background: Theory of Invention
The following is a discussion of the background theory of the
While we believe it to be technically accurate, we do not wish to be
by this theory since the operability of the invention has been
verified, as will be apparent from the later discussion.
We have recently worked work with the reception and utilization of
radio-frequency reception, e.g., for low-power utilization
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
First, we noted that the higher we placed an antenna above the
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
output was greatest at low tide and lowest at high tide. We believe
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
to a limited extent; these caused the antenna to produce a higher
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
times; at first we would not attribute any cause to these drops.
investigation enabled us to correlate these drops with the subsequent
of seismic activity. We found that the magnitude of the drop was
to the size of the subsequent earthquake.
Certain phenomena have been discovered to precede earthquakes.
include an anomalous uplift of the ground, changes in the electrical
of rock, changes in the isotopic composition of deep well water,
in the nature of small earthquake activity (e.g., bunching of small
anomalous ground tilt or strain changes, changes in physical
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
Phenomena associated with rocks have attracted much recent
Wm. Brace of the Mass. Inst. of Technology has found that when rocks
squeezed or compressed, just before they fractured, they tended to
hairline cracks, swell or dilate (dilatancy), become more porous and
conductive, and transmitted high frequency seismic-like waves more
Two of Brace's former students, Amos Nur of Stanford University and
Scholz of Lamont-Doherty furthered Brace's work, connecting the
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.
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
cause of this drop in antenna output as a precursor or predictor of
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
thereby causing the antenna's output to decrease temporarily.
Thus before the occurrence of a quake, the underground pressure
greatly temporarily, causing underground rock bodies to swell and
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
output and provide a suitable indication if the output level dropped
The indication was calibrated empirically after much experimentation so
as to filter out the effects of solar- and tide-caused variations. We
this by arranging the apparatus so that an output indication was
only if the antenna output dropped a predetermined degree beyond its
level; we utilized statistical filtering techniques to accomplish this.
Figure 1 shows the front panel of a Seismic
Warning (SEW) apparatus according to the invention.
Figure 2 is a plot of voltage (representing
rf level) v. time as measured by the apparatus of Figure 1.
Figure 3 is a schematic diagram of an ambient
module circuit (used in the SEW apparatus) for producing a DC output
proportional to the ambient rf energy
Figure 4 is a block diagram of a computer in
apparatus of Figure 1.
Figure 5 is a flowchart which depicts the
of the SEW system.
Figure 6 is a flowchart which depicts the
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
is provided as shown in FIG. 1. The apparatus consists of a housing
a general purpose computer (not shown), a disc drive 10, an analog
comprising a microampere meter 12 arranged to monitor direct current
is proportional to the ambient rf energy), and a direct current strip
recorder 14 arranged to provide a continuous indication of the current
antenna output, which will be called the ambient power level. A
keypad 16 is provided to enter data, such as time, for entering
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
24 is provided to display graphic and alphanumeric information of the
status of the apparatus and previous data records.
Lastly the apparatus includes four status-indicating lamps, which
are LEDs (light-emitting diodes) as follows: A green LED 26 indicates
the system is on and functioning normally. A yellow LED 28 indicates
the system has detected an event, namely the occurrence of a drop in
power below the preset level, which would be the prediction of an
earthquake. A red LED 30 is provided as backup confirmation of the
of the event; LED 30 is illuminated when a duplicate receiving system
detects an event. A blue LED 32 indicates initiation of operation of an
automatic telephone dialer within the system, which has been
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
all system data.
Figure 2: Ambient RF Level vs Time Before
Figure 2 illustrates a reproduction of an actual plot of a voltage
a function of time, which voltage was proportional to the ambient RF
frequency) level, from the period from before to after a relatively
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
antenna (not shown) which was mounted horizontally and which extended
San Francisco (Richardson) Bay easterly from Sausalito, California, 9
above sea level. The antenna thus intercepted and converted to an RF
the ambient RF energy, mainly from local (San Francisco area) AM radio
stations. We rectified and filtered the output of the antenna using
of the circuit of FIG. 3 (described below) to provide a DC voltage
was plotted on a conventional ink-on-paper plotter. Note that on the
of the chart for Apr. 19 (1984), which begins at time 0:00 (midnight)
ends at 24:00, the voltage or ambient RF power level at the antenna
and fell and then increased slightly in the 24-hour period. This
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
On Apr. 20, from about 8:00 to about 12:00, a sharp and
dip in the ambient rf power occurred, as indicated. The magnitude of
pronounced dip is far greater than the normal tide-caused variations,
is its beginning and ending slope.
Thereafter, from Apr. 20 to Apr. 23, the plot (not shown)
unremarkably, albeit with a slight variation from normal.
The same occurred on Apr. 24, with the plot actually being
similar to a normal day. However at 13:15 on Apr. 24, as indicated, a
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
made by the repeated observation of dozens of similar dips and
quakes. Pronounced dips were always followed by a quake several days
Thus we have empirically established causal and theoretical connections
between pronounced dips of the type shown and the occurrence of
Figure 3: Ambient Power Module
The circuit of Figure 3 is used to convert the ambient RF energy
a direct voltage which can be used and handled by data processing
Designated an ambient power module (APM), it is connected to an antenna
40, preferably a broadband monopole antenna of the type described in
preceeding section. The distal end of the antenna is free and its
end is connected to the circuit via two capacitors Cp1 and Cn1, each
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
it comprises two rectifiers (diodes) Dn1 and Dn2 (1N34 type) and a
capacitor Cn2 (40 microfarads). Rectifier Dn1 is connected in parallel
to the signal path and rectifier Dn2 is connected in series, in the
known voltage multiplier arrangement. Capacitor Cn2 is connected in
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
In operation, an RF voltage is developed across antenna 40; this
is voltage multiplied by the two rectifiers on each side of the
The resultant direct voltages are smoothed or filtered by capacitors
and Cp2 and are supplied to output terminals 42 and 44. A positive
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
invention and which is provided within the apparatus of Figure 1 is
in Figure 4. The computer receives the positive voltage from the APM
3) and processes this, providing an alarm if the voltage dips a
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
unit 52, which is a type 68000 microprocessor or computer on a chip.
52 and ADC 50 are clocked by a clock 54 in conventional fashion.
CPU 52 operates on instructions from a program contained in an
programmed read only memory (EPROM), the program being listed later.
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
printer 26', each of which was already described in conjunction with
CPU 52 can receive input data manually from hexidecimal keypad 16
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
the CPU to a phone (not shown).
As also indicated in Figure 4, the negative output of the AAPM of
3 is connected to ammeter 12 and chart recorder 14.
Figure 5: Flowchart of Seismic Early
In operation, the system of Figure 4 operates under control of the
in EPROM 56 in accordance with the flowchart of Figure 5 as follows:
Startup: Blocks 70 and 72: An initialization and start-up sequence
first initiated when the machine is turned on, as indicated by block
this sets all registers and counters to zero. The time and data are
set manually (using EPROM 56), as indicated by block 72.
Clock Reading: Blocks 74 and 76: Next, under automatic program
the machine reads the elapsed time on its clock display register, as
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
minute, the decision in block 76 will be "yes", so that the machine
take one sample of the rectified, smoothed, and digitized version of
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
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,
the number of samples accumulated, and dividing the running total by
latest number of samples each time a new sample is taken.
Store Hourly Average: Blocks 82 and 84: Next, as indicated in
82, a test is made to see if the time display register indicates that
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
makes a test to see if 24 hours have passed. If not, the machine will
be able to make any valid statistical determinations. Thus it must run
at least 24 hours before being operative. Assuming the decision in
86 is negative (24 hours have not yet elapsed) another test is made
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
will be read again (block 74) in the usual loop.
Calculate SD: Block 86 ("Yes") and Block 88: If a full day has
so that valid statistics can be calculated ("yes" from block 86), the
deviation (SD) of the last 24 hourly averages is calculated, as
in block 88. This is done once per hour. The calculation is made using
the usual SD formula
where SDDEV=SD; SQR=the square root; sum=the sum of; x=the
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
of each hourly average from the mean, squaring each deviation, taking
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
than 0.3. This value has been empirically determined to be the level at
which the present apparatus will provide a reasonably positive
that an earthquake will occur, while neglecting the effects of
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
the average of the last 24 hourly samples, so that no alarm need be
I.e., the antenna's output did not drop significantly to indicate an
earthquake. Thereupon the program moves to block 94, where a test is
for the existence of hour zero, as described. If, however the SD
0.3 ("yes" output of block 90), this indicates that the antenna's
has dropped significantly so as to affect the last hourly average,
to indicate an impending earthquake.
Alarm: Block 92: In response to the Yes output of block 92, an
is triggered (block 94). The alarm may be a bell, the dialing of a
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
of the Flowchart of Figure 6, the alarm trigger sequence. To eliminate
the possibility of equipment failure and to provide confirmation from
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
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
in the registers will be stored to disc to create a permanent record
the registers will be cleared to create new data for the next day.
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
block 96, the clock is read again in accordance with the regular
Figure 6: Alarm Trigger Flowchart
The sequence of Figure 6 is performed when the alarm is triggered
block 92 of Figure 5 as an optional, but preferred backup confirmation
of an impending earthquake. The operations in the backup confirmation
will be described briefly.
Beginning with blocks 100 and 102, the system is continually
(hourly) for the occurrence of a SD of the hourly averages of greater
0.3. If the SD is greater than 0.3, the alert indicator (28 of Figure
is triggered (block 104) and the program initiates a test (block 106)
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).
the backup does not indicate an excess SD, the indicators are reset to
normal (block 112), but if backup confirmation is received, the alarm
(30 of Figure 1) is triggered per block 114 and a preprogrammed
number is dialed and indicator 32 is lit (block 116).
After the alarm condition is manually checked and the system is
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
civil authorities will have time (usually several days) to notify the
evacuate the area, or take any other needed precautions, depending on
size of the impending quake as indicated by the size of the standard
The attached computer programs will perform the calculations and
above described. These programs are written in the BASIC programming
Program "RECVOLT.AL" runs continuously and writes the information to
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
not be construed as limitations on the scope of the invention, but
as an exemplification of one preferred embodiment thereof. Many other
are possible. For example, the programming language can be changed, or
the calculations and operations can be performed with hard-wired
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
a special, dedicated transmitter with a special, dedicated frequency
a specially-tuned matching receiver can be used to avoid dependence on
stations which are not under the control of the earthquake prediction
and its personnel. The transmitter and the receiver should be spaced
geographically, preferably by at least several km, so that the ground
conduction phenemonon can operate. Also the transmitted signal can be a
specially-coded or modulated signal, or it can be an auxiliary signal
a regular transmitter, e.g., a SSB or SCA signal, together with a
receiver. In lieu of a test for an excess SD, the apparatus can be
to test for a predetermined drop in the value of the antenna output
its immediately previous value or its average value over a
period, such as an hour or day, or for a drop having greater than a
slope. Accordingly the full scope of the invention should be determined
by the appended claims and their legal equivalents, and not by the
Claims -- [ Not included here ]
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