The South West Pacific: The Kermadec Trench
Two earthquakes of M6.1 and M5.6 draw attention to the Kermadec Trench. A part of the complex and convoluted boundary between the Pacific and Australian plates, this area is in fact fairly simple in terms of its tectonic setting. Here, the Pacific subducts westwards beneath the Australian plate (in contrast to the situation further north and west, where the direction of subduction is reversed) along the Kermadec Trench.
The two sub-marine shallow-intermediate earthquakes recorded here had their epicentres in the over-riding (Australian) plate and probably occurred along the interface between the two plates. Although both occurred underwater, neither was large enough to generate a tsunami, even if vertical movement was involved, as seems likely at a subduction zone.
Largest Earthquake in the USA: M5.1, Nevada
The largest tremor to strike the USA was an M5.1 which occurred in the mountains of Nevada. Although detailed information isn’t available, cross-referencing the USGS record of the ‘quake against maps of local faults (Yeats) indicates that it probably occurred as a result of slippage on or in the region of the Fish Lake Valley fault. Faults in the area are typically northwest-southeast trending with dominant strike-slip motion and make up a belt which forms a boundary between two generally stable crustal blocks, the Sierra Nevada block and the Basin and Range block.
The most unusual tremor of the week, the M6.6 in Siberia, is noteworthy because of its size and the area in which it occurred. The limited population in the area, however, demonstrates that the significance of an earthquake is partly defined by the population (or lack thereof) affected.
USGS. Real time earthquake map. (2013). Accessed February 19, 2013.
USGS. Seismicity of Russia and the Former Soviet Union. (2012). Accessed February 19, 2013.
Yeats, R. Active Faults of the World. (2013). Cambridge University Press.
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