abstract

During the CANNIKIN underground nuclear test of November 6, 1971, nearsurface earth deformations were observed by a total of 26 strainmeters and eight tiltmeters at nine sites in the Aleutian Islands at distances of 10 to 1125 km from ground zero on Amchitka Island. Permanent strain steps were observed at all stations. The size of strain steps observed at about 10 km (> 10−4) implies that the zone of nonelastic behavior extended to more than 10 km from ground zero. The size of strain steps observed at 295 and 1125 km (< 10−8) indicates that the residual strains at these distances were not as large as the amplitude of the daily earth tide. The permanent steps exhibit a pronounced directional assymmetry but, at five stations, are in reasonable agreement with predictions based on the work of Wideman and Major (1967). Redundant observations of areal strains at two stations yield values of −29.5 × 10−9 versus −24.2 × 10−9 and −2.1 × 10−7 versus −3.2 × 10−7.

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