New Zealand Journal of Geology and Geophysics abstracts
Strong motion modelling of the 1993 Tikokino earthquake, southern
Hawke's Bay, New Zealand
RACHEL E. ABERCROMBIE*
RAFAEL A. BENITES
Institute of Geological & Nuclear Sciences
P.O. Box 30368
Lower Hutt, New Zealand
*Present address: Department of Earth and Planetary Sciences, Harvard
University, 20 Oxford Street, Cambridge, MA 02138, USA.
Abstract The 1993 Tikokino, New Zealand earthquake (ML
6.1) is modelled as a unilateral rupture, exhibiting clear source directivity
to the south. The earthquake was recorded by four strong motion stations within
30 km: Waipawa to the south, and three sites in Napier and Hastings to the
northeast. The shorter duration and greater amplitudes (by a factor of 10)
observed at Waipawa with respect to the other stations provide clear evidence
for the southward rupture direction.
The Tikokino earthquake occurred on a shallow dipping, oblique reverse fault,
and probably represents movement at the plate interface. A high rupture
velocity is required to match the distribution of observed ground shaking, and
the rupture area is constrained to be c. 7 x 2 km2. The
moment of the preferred model is 1.1 x 1018 Nm (Mw 6.0)
and the stress drop about 35 MPa. This high average stress drop is
consistent with the rupture being confined to an isolated asperity.
The model used consists of a finite, rectangular fault rupturing with
prescribed velocity and direction, and with uniform slip. The fault is embedded
in a planar layered seismic velocity structure. The ability of the model to
match the principal features of the observed seismograms suggests that it will
be a useful tool in the prediction of strong ground motion for seismic hazard
studies in the region.
Keywords earthquake source directivity; strong ground motion;
plate interface thrust; extended fault model
New Zealand Journal of Geology and Geophysics, 1998, Vol. 41: 259-270
0028-8306/98/4103-0259 $7.00/0 (c) The Royal Society of New Zealand
1998
PDF file of entire paper: medium quality (1140K); (scanned from paper original: notes about this process)
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