Pukaki microearthquake network final report

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Reyners, M.E. 1986 Pukaki microearthquake network final report. : . Report / Geophysics Division 211 20 p.

Abstract: This report provides details of the operation and scientific results of the Pukaki microearthquake network, from its installation in June 1975, till its removal in November 1983. During the 3, 078 days of network operation 2825 earthquakes of magnitude ML > 0.8 were located, the largest having a magnitude of ML = 4.6. The microearthquake network has revealed that the addition of 5.5 x 109 m3 of water to Lake Pukaki resulted in widespread seismicity changes which correlate closely with groundwater level changes. These seismicity changes suggest that most of the earthquakes induced by the raising of the lake level were caused by the indirect effect of stress concentration around the edges of a weakened zone, rather than by the direct effect of the increase in pore pressure. As well as being extremely valuable in monitoring reservoir- induced seismicity, the Pukaki microearthquake network proved very useful for a variety of seismological studies, ranging from crustal structure determinations to nuclear explosion detection. (auth)