Volcanic Earthquakes: M4.6 in Hawaii
Not a major earthquake in global terms, but certainly notable within its tectonic setting was the M4.6 which occurred on the island of Hawaii. The Hawaiian Islands are thousands of miles from the nearest plate boundary, and seismic activity there is related to their volcanic nature. Hawaiian volcanism is not, as in many other areas, the result of subduction: instead it results from a deep plume of hot rock which rises through the mantle to reach the surface. Such plumes are not uncommon and account for many other mid-plate volcanic islands.
Earthquake activity in such areas results either from faulting generated by magma-related earth movements, or from the injection of magma into a volcano: in these cases, they may offer clues about the imminence of an eruption. Such earthquakes are very common on Hawaii and are often precursors to eruptions. And though major earthquakes are not common they do occur: the USGS historic earthquake listing shows ten of ≥M6.0 in the past two centuries, the largest reaching a reported magnitude of M7.9.
Recent Earthquakes: Is the Earth Getting Calmer?
Over the past few weeks there have been periods of relative quiet with few major earth tremors reported. Earthquakes are, of course, unpredictable: and while we can reasonably expect a certain number of a given magnitude in a given period of time, such a period of relative quietude does not represent a slowing in seismic activity worldwide.
USGS. Hawaiian Volcano Observatory: Seismicity. (2013). Accessed January 8, 2013.
USGS. Historic earthquakes List. (2013). Accessed January 8, 2013
Yeats, R. Active Faults of the World. (2012). Cambridge University Press.
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