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| Titel: |
Source mechanisms and strong ground motion from the 1982 Wonnangatta and the 1966 Mount Hotham earthquakes |
| Auteur: |
Denham, D. Gibson, G. Smith, R. S. Underwood, R. |
| Verschenen in: |
Australian journal of earth sciences |
| Paginering: | Jaargang 32 (1985) nr. 1 pagina's 37-46 |
| Jaar: |
1985-03 |
| Inhoud: |
The Wonnangatta earthquake of 21 November 1982 took place about 190 km NE of Melbourne, It was felt throughout eastern Victoria and southeastern New South Wales and the radius of perceptibility was about 195 km. Because the earthquake occurred in the middle crust (∼17 km) and the epicentral area was uninhabited, no damage could definitely be attributed to the earthquake and the highest reported intensity was VI on the Modified Mercalli Scale. The main earthquake was followed by 29 aftershocks that were large enough to be located and helped define the causative fault. The focal mechanism of the main earthquake was well constrained and the major double couple had a strike of 357°, a dip of 52° and a slip angle of 52°. This mechanism is consistent with horizontal compressive stresses acting NW-SE in the crust, as observed from other earthquakes in the region. The magnitudes of the main earthquake were estimated to be 3.8 Ms, 4.8 mb and 5.4 ML and the seismic moment of about 6.3 x 1015 N m or 1.0 x 1017 N m, depending on whether the estimates are based on MS or ML values. Strong ground motion was recorded at two acclerographs sited 87 and 137 km from the hypocentre, and accelerations of 160 and 75 mm s2 were recorded, respectively. The 1982 Wonnangatta earthquake occurred only about 25 km from the 1966 Mount Hotham earthquake, which was studied by Underwood (1967). In some respects these two earth quakes are very similar: the magnitudes of the 1966 event were 3.8 Ms, 4.7 mb and 5.5 ML—almost identical to the Wonnangatta earthquake—and both earthquakes occurred in the middle crust. How ever, the similarities end there. The isoseismal maps from the two events are dissimilar. The 1966 earthquake produced isoseismals elongated in a NW-SE direction and consequently it was barely felt in Melbourne, whereas the 1982 earthquake produced NE-SW trending isoseismals and it was felt throughout the city. Re-examination of the first motion data from the Mount Hotham earthquake (from which it was not possible to obtain a focal mechanism at the time) indicates possible normal faulting, with a NE-SW T-axis. It is not clear how the two different types of earthquakes are related but we presume that the normal faulting event represents a response to regional uplift caused by NW-SE compressive stresses. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 7 van 8 gevonden artikelen
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