How damaging was today’s Russian earthquake?
An earthquake of magnitude 6.9 (M6.9) struck in the north-western Pacific off Russia’s Kamchatka peninsula on 28 February 2013. At the time of writing, no damage or injuries had been reported. Although the ‘quake was large, at a subduction zone and occurred underwater, no tsunami warning was issued, suggesting that movement along the fault line which caused the tremor was horizontal rather than vertical – if movement was vertical, it was insufficient to displace a significant volume of water.
Russian Earthquake: Tectonic Setting
The earthquake took place at the southern end of the Kamchatka peninsula and the northern end of the Kuril Arc, both of which form part of the so-called Pacific Ring of Fire and are located on the boundary between the Pacific tectonic plate and a southwards extension of the North American late (sometimes called the Okhotsk microplate). The epicentre of the February 28 tremor lies north of the location of the devastating 2011 Tohoku-oki earthquake.
The Kuril Arc is a subduction zone – the eastward-moving Pacific plate collides with and is forced under the Okhotsk microplate (or N American plate) at the Kuril Trench. At 52km depth and with an epicentre in the overriding plate, it appears that the February 28 tremor was the result of movement at or near the contact between the two plates.
Kamchatka and the Kuril islands form part of a chain of volcanoes associated with the subduction zone: Subducting rock melts at high temperatures and pressures. Being less dense than the surrounding rock, the molten rock rises to the surface where it finds expression in this chain of submarine, island and terrestrial volcanoes.
Historic Seismicity of the Area
Unsurprisingly, given the active nature of the boundary, earthquake activity is common and the most recent M6,9, though significant, is by no means unusual in magnitude for its setting. Geologist Robert Yeats describes several historic Kuril Islands earthquakes, the catalogue including a number exceeding M8.0. The largest of these, an M9.0, struck not far from the epicentre of the most recent earthquake in 1952, and ranks as the 3rd largest tremor of the 20th century.
Data from the USGS verify the status of the Kuril Arc-Kamchatka region as highly seismically active – they clearly demonstrate that Russia’s largest earthquakes of the past century have occurred in this zone, listing 12 tremors of at least M6.6. The most recent, while not as large as some of the mega-quakes to have occurred here, is the largest in the region since 2009. The arc also saw earthquakes of greater than M8.0 in both 2006 and 2007.
Earthquakes: Looking to the Future
It’s worth noting that Yeats considers so-called seismic gaps (areas where no major earthquake has been recorded within a long period of time) in the Kuril island-Kamchatka zone. One such gap lies to the south of the February 28 epicentre and one to the north. Although seismic gaps are identifiable as areas of relative quiescence (and usually areas where strain continues to build up prior to being released by earthquake activity) no great success has yet been achieved in terms of linking their spatial distribution with prediction of future tremors.
USGS. Historic earthquakes – Russia. (2013). Accessed February 28, 2013.
USGS. M6.9 – 85km SE of Ozernovskiy, Russia. (2013). Accessed February 28, 2013.
Yeats, R. Active Faults of the World. (2013). Cambridge University Press.
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