Seismic warning system using RF energy monitor

Details Seismic warning system using RF energy monitor Seismic warning system using RF energy monitor

1985-01-28

1986-12-09

Swann, III, Glen R.

Communications: electrical

Condition responsive indicating system

Specific condition

340600, 340690, G08B 2100

Patent

active

046282998

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.

REFERENCES:
patent: 4214238 (1980-07-01), Adams et al.
patent: 4364033 (1982-12-01), Tsay

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