A micro-earthquake survey of the Benmore-Pukaki region: February-March 1973

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Adams, R.D.; Robinson, R.; Lowry, M.A. 1974 A micro-earthquake survey of the Benmore-Pukaki region: February-March 1973. : . Report / Geophysics Division 86 15 p.

Abstract: During the 18-day survey of micro-earthquakes near Lakes Benmore and Pukaki, 32 events with magnitudes between 1.9 and -0.4 were located. These fall mainly in four groups, each a few kilometres across, two of which are near positions assigned to magnitude 5 earthquakes that followed the filling of Lake Benmore. The positions of the micro- earthquakes, and of larger events located using the standard New Zealand seismograph network, suggest that the activity forms two main trends, one roughly N-S from the west of Lake Pukaki to Omarama, and the other extending NE from the northern arm of Lake Benmore. A composite focal mechanism plot suggests strike-slip faulting in directions displaced about 15deg clockwise from NE-SW, NW-SE. This mechanism is consistent with a general E-W compression, as observed elsewhere for shallow earthquakes in the South Island, and as indicated by recent reverse faulting parallel to the N-S trend of earthquakes (auth.)