Postseismic deformation recorded by small survey networks following the 1987 Edgecumbe earthquake, New Zealand

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Abstract
Following the 1987 March 2 Edgecumbe earthquake, six small-aperture (c. 250 m) survey networks were established in the Rangitaiki Plains to monitor horizontal and vertical postseismic deformation across faulttraces formed during the earthquake. Results indicate that both horizontal and vertical deformation have continued since the earthquake across the area covered by the networks. Across the Awaiti Fault the vertical deformation is in the opposite sense to that which occurred during the earthquake, whereas across the Edgecumbe and Te Teko Faults it is in the same sense. At one site across the Edgecumbe Fault, where both horizontal and vertical observations were made, between March 2 and November 17, c. 60 mm of vertical movement and c. 17 mm of horizontal movement occurred. Results show that a portion of the vertical deformation may be compaction of near-surface materials but that, in pan, it is likely to be a result of continued slip on the Edgecumbe Fault.