The Richter earthquake magnitude scale in South Australia
Titel:
The Richter earthquake magnitude scale in South Australia
Auteur:
Greenhalgh, S. A. Parham, R. T.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 33 (1986) nr. 4 pagina's 519-528
Jaar:
1986-12
Inhoud:
Richter magnitudes ML have been determined for 718 well recorded South Australian earthquakes by converting amplitudes derived from existing seismograph stations to equivalent Wood-Anderson amplitudes, and substituting in Richter's formula (Richter 1935), derived for such instruments and for Southern California. The magnitudes so determined were generally found to increase with distance A for each earthquake, at least for events at distances below a few hundred kilometres, reflecting lower attenuation of crustal S waves in South Australia. A distance-dependent correction, which must be subtracted from Richter magnitudes, was obtained by integrating the weighted least squares fit to the (A, dML/dA) data. The correction increases to one-half of a magnitude unit at a distance of 400 km, and thereafter decreases smoothly to 0.3 units at 600 km. Station corrections, due to local geological variations, have also been determined. Values range from -0.6 to + 0.2 units. Empirical relationships between the revised ML scale and the previously used local magnitude scales mL and MN (White 1968; Stewart 1975) and the body wave magnitude scale mb have been established. The latter yields results consistent with the well known Gutenberg-Richter formula (Richter 1958)
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