Thirty years of seismic network recording in South Australia: Selected results

Details Thirty years of seismic network recording in South Australia: Selected results Thirty years of seismic network recording in South Australia: Selected results

Nov 1994

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994pepi...86..277g&link_type=abstract

Physics of the Earth and Planetary Interiors (ISSN 0031-9201), vol. 86, no. 4, p. 277-299

Physics

1

Australia, Earthquakes, Networks, Seismic Waves, Seismographs, Seismology, Calibrating, Computer Techniques, Digital Systems, P Waves, Propagation Velocity, S Waves, Wave Propagation

Scientific paper

The year 1993 marks 30 years of seismic network recording of earthquakes in South Australia. The network currently comprises 17 short-period instruments, of which six use digital recording and five employ triaxial sensors. Approximately 350 earthquakes are located within the State each year using a computerized seismic analysis system developed by the Phillip Institute of Technology. A duration-based magnitude scale, equivalent to the Richter M(sub L) scale, has been developed for most stations. The pre-network (historical) record of earthquake activity in South Australia dates back to 1837. Epicenters are available for just 45 earthquakes. Of these, ten are of magnitude five or greater. The instrumental data over the last 30 years show a similar trend in epicentral pattern to the historical earthquakes, with the major zones being the Flinders Ranges, Eyre Peninsula and the Southeast. There have been 40 earthquakes of magnitude four or greater since 1963, the largest earthquake being of magnitude six in the Musgrave Ranges during 1986. Mine and quarry blasts within the State have been useful in calibration of the network, both in terms of hypocentral location and amplitude studies. The explosions have also furnished valuable information on the crustal velocity distribution. Epicentral co-ordinates of mine blasts are generally good to within 3-5 km. The explosions yield Richter magnitudes of one (charge size 1 or 2 tons) to 2.5 (charge size 50 tons). The crustal S waves, used in earthquake magnitude determinations, exhibit an amplitude-distance decay coefficient of 1.2. The P-wave velocity function of the crust increases non-linearly with depth, from about 5.0 km /s near the surface to 6.4 km /s at 20 km depth, where the gradient reduces, with the velocity reaching a value of about 7.4 km /s at a depth of 40 km.

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