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Source Characterization of the October 30, 1983 Narman-Horasan Earthquake
Eric R. Shortt
Submitted
to the Department of Earth, Atmospheric, and Planetary Sciences on September
1, 1985 in partial fulfillment of the requirements for the degree of Master
of Science
Abstract
Source parameters are determined for the October 30, 1983, Narman-Horasan
earthquake in northeastern Turkey, Ms = 6.9, using far-field body wave and
near-field synthetic seismograms. A double-couple point source is obtained
from the inversion of teleseismic P and SH long period WWSSN and GDSN data.
The preferred source mechanism is left lateral strike-slip with a small thrust
component (strike = 215°, dip =64°, slip =7°). The centroid depth
is estimated at 10 km and the seismic moment at 8.0X1025 dyn-cm. The duration
of the source time function is approximately 5 s.
Dimensions of an assumed rectangular fault are determined from the point source
solution and aftershock distribution. Fault width is estimated at 13 km and
length at 15 km. Based on these values the average displacement on the fault
is 1.2 m. It is speculated that source region structure is responsible for
the complicated nature and long duration of the body wave records.
Forward modeling of the single three-component strong motion record from a
station 25 km south of the epicenter is carried out using a discrete wavenumber
calculation. The study reveals that the rupture to the southwest, propagating
at sub-shear velocity, explains the outstanding characteristics of the processed
displacement records. A to 1 km thick low velocity surface layer representing
sedimentary cover is an essential part of the model.
