The University of Saskatchewan Seismograph Network
Date
1992
Authors
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ORCID
Type
Degree Level
Masters
Abstract
This thesis discusses the work completed on the
University of Saskatchewan Seismograph Network (USSN). The
main thrust of the work was the development of an automatic
seismic data monitoring algorithm and interactive computer
packages which are used to analyze digitally recorded
earthquakes. Currently the monitoring package detects two
earthquakes, on average, daily. Seven earthquakes within
1500 km of the USSN were detected between the period of
September and December of 1991.
The interactive computer packages are used to provide
earthquake information such as location, magnitude, and
spectral parameters. Instrument calibration is a vital
component of the analysis package. A reliable calibration
function has been derived for the system by studying the
instrument response to known ground-motions, which were
introduced into the seismometers electronically.
A direct benefit of the USSN will be a better
understanding of seismicity in Saskatchewan and the rest of
western Canada. The utility of the network is evaluated by
studying the magnitudes of earthquakes which can be reliably
recorded. The event resolvibility is limited by the
background noise level, whereas the maximum recordable event
size is controlled by the inherent limitations of the
seismographs. The recording range of the instrumentation is
v
established using results from both an ambient background noise
study and instrument calibration experiments. The
investigation shows that earthquakes from southern
Saskatchewan, which have magnitudes between 2.5 and 4.0, can
be reliably recorded (based on the present seismograph
configuration) .
Accurate earthquake location requires a keen
understanding of the seismic velocity variations within the
crust and upper mantle (a crustal model). Earthquake data
recorded by the USSN were interpretated to develop a crustal
model for the Saskatoon area. The study used seismograms
recorded between epicentral distances of 200 and 11 000 km.
The interpretation shows that the depth to the base of the
crust (Moho), under Saskatoon, is 46 km. Refractions along
the Moho, from regional distance earthquakes, have apparent
P-wave velocities of 8.3 km/sec. The P-wave velocity in the
upper crust is 6.16 km/sec.
The crust, in this area, is found to be complicated,
based on the teleseismic and local earthquake data. P-waves
from teleseismic earthquakes show travel time deviations as
large as 0.4 sec, which may be related to the fractured
nature of the crust. The existence of an inter-crustal
discontinuity is suggested by seismograms from a local
earthquake. The observed P-wave refractions are consistent
with a horizon at 20 km depth, which has a dip of 4.5 deg,
and a P-wave velocity of 6.6 km/sec.
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Citation
Degree
Master of Science (M.Sc.)
Department
Geological Sciences
Program
Geological Sciences