Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Earth science
Reexamination Certificate
1999-08-25
2001-06-12
McElheny, Jr., Donald E. (Department: 2862)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Earth science
Reexamination Certificate
active
06246964
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a method for predicting earthquakes.
Large earthquakes are among the most destructive of natural disasters. The toll that these disasters have taken in both lives and property is well known and need not be recited here. Many methods have been proposed in the past for predicting earthquakes, to provide enough warning for the people affected to prepare. One geophysical method, for example, based on the gravitational field turbulence associated with a seismic event, was proposed by Chiba (Jiro Chiba,
Proceedings of The Institute of Electrical And Electronic Engineers,
1993
International Carnahan Conference on Security Technology
, pp. 215-218). Another geophysical method, based on measurements of natural low frequency radio signals, was proposed by Hayakawa (M. Hayakawa,
Phys. Earth. and Plan. Int.
, vol. 77 pp. 127-135 (1993)). These methods provide only about 20 seconds advance notice of an earthquake.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method for predicting earthquakes that provides more advance warning than known methods.
SUMMARY OF THE INVENTION
According to the present invention there is provided a method of predicting an earthquake in a seismically active region below an ionosphere, comprising the steps of: (a) measuring a relative fluctuation of plasma density in the ionosphere; (b) inferring a relative amplitude of an acoustic-gravity wave in the ionosphere; and (c) inferring an earthquake magnitude from the relative amplitude of the acoustic-gravity wave.
The present invention is based on the discovery of an earthquake precursor that appears in the ionosphere above the epicenter several hours before the earthquake.
FIGS. 1A through 1F
show two way travel times of reflections from the ionosphere, as a function of frequency, measured by a vertical ionosonde, in the 24 hours before an earthquake that occurred in the Vrancha region of Romania on May 30-31, 1990.
FIG. 1A
shows the structure of the normal ionosphere, 24 hours before the earthquake. Only one reflecting layer is present, and it reflects only at frequencies up to about 15 MHz. As the time of the earthquake approaches, more reflecting layers develop, and they reflect over a wider range of frequencies. Because the reflection frequency is proportional to the square root of the ion density, this wider range of frequencies indicates that the ionosphere becomes more inhomogeneous above the epicenter in the 12 to 16 hours before the earthquake. These inhomogeneities are believed to be produced by acoustic-gravity waves (AGW) associated with the buildup of strain in the Earth's crust immediately before the earthquake.
This phenomenon provides up to 20 hours warning in advance of an earthquake, but it does not provide a measure of the magnitude of the impending earthquake. According to the present invention, a measure of the magnitude of the earthquake is provided by measurements of oblique scattering of radio waves from the ionospheric inhomogeneities. These measurements are interpreted using a theory of the coupling of AGW and ionospheric plasma density that is presented herein.
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Blaunstein, N., “Evolution of a Stratified Plasma Structure Induced by Local Heating of the Ionosphere”,J. Atmospheric and Solar-Terrestrial Physics, 59(3): 351-361, 1997.
Blaunstein et al, “Radiophysical Methods of Investigation of Anomalous Effects in the ionosphere During Seismic Events Preparation”, XXIV Gen. Assemb. Internl. Union of Radio Science, Kyoto, Japan, 1993.
Chiba, J., “Signal Processing of Gravitational Field Detector for Prediction of Large Seismic Waves”, Proc. IEEE, Oct., 1993, pp. 215-218.
Philipp et al, “Power of HE-Scatter Signals” Proc. XII Union Conf. Radiowave Propagation, Kharkov, USSR, 1978, pp. 407-411.
Friedman Mark M.
McElheny Jr. Donald E.
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