Motion of the ground induced by the CANNIKIN and MILROW nuclear explosions beneath Amchitka Island was observed at vertical arrays of subsurface stations in borings offset 90 m from the shot holes and at surface stations at distances ranging from surface zero to about 10 km. Acceleration, particle velocity, and displacement time histories were obtained: vertical components only in the vertical arrays and three orthogonal components at surface stations.

MILROW results indicate Rayleigh waves in records from a horizontal range of one-half shot depth and beyond. Analysis showed the initial spall depth near 110 m, with later spallation below 150 m and between 30 and 90 m. Surface data indicate spallation extended laterally to four times shot depth. CANNIKIN data were trucated at about 1.8 sec by power circuit malfunction. Peak motion was recorded at all but the most remote CANNIKIN station before loss of power. Comparison of CANNIKIN data with those from MILROW indicate greater peak motions from the more energetic CANNIKIN explosion, but scaled peak motions from these events are similar.

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