New Zealand Journal of Geology and Geophysics abstracts
Multiple-mainshock events and long-term seismogenesis in Italy and
New Zealand
Frank Evison*
Institute of Geophysics
School of Earth Sciences
Victoria University of Wellington
P.O. Box 600
Wellington, New Zealand
David Rhoades
Institute of Geological & Nuclear Sciences
P.O. Box 30 368
Lower Hutt, New Zealand
*Deceased
Abstract The phenomenon of the precursory scale
increase (ψ), on which the three-stage faulting model of long-term
seismogenesis is based, has previously been studied in relation to
mainshock/aftershock events, and clusters of such events, in
California, Greece, Japan, and New Zealand. The tectonic environments
of the studied events have comprised subduction, continental collision,
and continental transform. In Italy, the study is now extended to large
multiplet-type events and to extensional tectonics. New Zealand
provides further examples of large multiplets. The results show that
multiplets, interpreted as multiple-mainshock events, are preceded by
the same ψ-phenomenon as the types of event previously studied. ψ again
provides estimates of the location, start time, and magnitude level of
the multiplet. It is concluded that the long-term seismogenic process
that explains previously studied occurrences of the ψ-phenomenon,
occurs equally with multiplets, and in conditions of extensional
tectonics.
Keywords seismogenesis; multiplets; precursory
seismicity; Italy; New Zealand
G04026; Received 24 June 2005; accepted 20 December 2005; Online
publication date 22 August 2005
New Zealand Journal of Geology & Geophysics, 2005, Vol. 48:
523–536
0028–8306/05/4803–0523© The Royal Society of New Zealand 2005
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