Abstract

The total apparent energy was computed for seismic waves on seismograms obtained at distances of 6.78 and 13.2 km from a blast of 1,221,000 lb of explosives and 22.0 km from a blast of 2,138,000 lb of explosives, at Promontory, Utah. The ratios of the total apparent seismic energy at these distances to the total energy of the explosives were plotted against distance, and the ratios of 0.027 and 0.017 were obtained by extrapolating this plot to zero and 2 km distance from the blasts, respectively. Using the relationship between total apparent seismic energy and magnitude given by Gutenberg and Richter (1956), magnitudes ranging from 4.0 and 3.9 (charge size of 490,500 lb) to 4.6 and 4.4 (charge size of 2,138,000 lb) were computed from the data applicable at zero and 2 km from the large quarry blasts detonated at Promontory and Lakeside, Utah, between 1956 and 1959.

For charge sizes ranging from 490,500 lb to 2,138,000 lb, an approximate linear relationship was found to exist between charge size and average record amplitude of the first cycle of the first arrival as measured on vertical-component seismograms obtained at Eureka, Nevada. The average vertical-component displacement amplitude of the first cycle of the first arrival was calculated to diminish by the 1.7 power of the distance between 6.78 and 22.0 km from the above blasts. The average vertical-component velocity amplitude of the first two cycles of the first arrival was calculated to diminish by the 1.8 power of the distance between 90.0 and 279 km from the above blasts.

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