Tectonics of the Indonesian Earthquake
The week’s largest earthquake was an M6.3 occurring to the south of Indonesia and the north of Australia: it was part of a cluster of seven tremors of greater than or equal to M4.0.
Tectonically, the region is dominated by the subduction of the Australian plate against the Eurasian Plate. This is, however, by no means the whole picture, which is complicated by the existence of many microplates squeezed along the zone between the two larger plates. Here, different types of boundaries create different and conflicting stresses, with the result that the whole of the region is highly tectonically active.
Earthquakes in the Indonesia-Papua New Guinea Region, 3-9 October 2012 -Image courtesy USGS
The map shows that earthquake activity along the diffuse boundary is common, and within this context an earthquake of M6.3, which would be considered significant elsewhere, is by no means atypical in a region which has been the location for some of the world’s largest and most damaging seismic events.
Tectonic Activity This Week
Without any major earth tremors, the week nevertheless showed that the planet remains constantly active. Where more detailed data are available, areas of recent activity continue to show a multitude of minor aftershocks – most notably, the cluster of minor tremors off the British Virgin Islands and in southern California, where almost 200 earthquakes of less than or equal to M4.0 were recorded.
Sources
Bergman, Eric A. and Solomon, Sean C. Source mechanisms of earthquakes near mid-ocean ridges from body waveform inversion: Implications for the early evolution of oceanic lithosphere. (1984). Journal of Geophysical Research. Accessed 9 October, 2012.
United States Geological Survey. Real time earthquake map. (2012). Accessed 9 October, 2012.
United States Geological Survey. Seismotectonics of the New Guinea Region and Vicinity. (2012).Accessed 9 October, 2012.
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