The recent spell of relative seismic calm for the planet continued in the week of January 23-29, 2013. Although there were more earthquakes at the larger end of the scale (i.e. ≥ magnitude 5 (M5.0)) compared to the previous week, there were no major tremors. The majority of the reported earthquakes occurred around the Pacific and in the eastern Indian Ocean, although one or two outliers deserve a mention.
The Week’s Largest Earthquake: M6.0, Kazakhstan
Although a glance at the map seems to show that the largest tremor of the week, on January 28, had its epicenter some distance away from the nearest tectonic boundary, this isn’t actually the case. Although the collision zone between the Indian and Eurasian plates is found south of the Himalayas, the zone of mountain building resulting from this collision is diffuse and all of the mountainous region, extending hundreds of miles into China and central Asia, is affected by the resulting seismicity.
With different relative movements, such zones are structurally complex and, without detailed information, it is difficult to say for certain which type of movement caused this particular event. However, a map of the fault zones in the area suggests that the point where the epicenter was recorded, close to the boundary between Kazakhstan and Kyrgyzstan, is characterized by active reverse faults. Therefore, it seems likely that this was the responsible mechanism.
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