Seismic warning system using RF energy monitor
First Claim
1. A method for providing an early warning of the future occurrence of an earthquake, comprising the following steps:
- (a) measuring the field strength of at least one broadcast radio frequency signal at a location separated from the place of transmission of said signal, and(b) providing a humanly-sensible indication if the strength of said signal decreases beyond a predetermined amount from a previous value thereof.
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Accused Products
Abstract
The ambient broadband radio frequency field strength from broadcast stations is monitored (FIG. 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 (FIG. 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.
24 Citations
20 Claims
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1. A method for providing an early warning of the future occurrence of an earthquake, comprising the following steps:
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(a) measuring the field strength of at least one broadcast radio frequency signal at a location separated from the place of transmission of said signal, and (b) providing a humanly-sensible indication if the strength of said signal decreases beyond a predetermined amount from a previous value thereof. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A system for providing an early warning of the future occurrence of an earthquake, comprising:
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(a) means for measuring the field strength of a least one broadcast radiofrequency signal, said means being arranged to measure said field strength at a location separated from the place of transmission of said signal, and (b) means responsive to the measured strength of said signal for providing a humanly-sensible indication if said measured field strength decreases beyond a predetermined amount from an average value thereof. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification