Secular strain measurements before and after the CANNIKIN nuclear test

Secular earth-strain measurements have been made in the central Aleutian Islands during the years 1970 and 1971. An annual variation of about 3 × 10−6 is evident on all records. A residual deformation of less than 3 × 10−6 per year is detected on most records. The state of strain near Amchitka Island, Alaska, at the time of CANNIKIN, November 6, 1971, differed from the state of strain at the time of the MILROW test, October 2, 1969, by less than 1 × 10−5. The strain records also contain novel episodes of large size (1-3 × 10−6) and high strain rate (1 × 10−7 / hr).