Newswise — COLLEGE PARK, Md. - The devastating Japan earthquake is the latest in a series of 'mega-quakes' over the past seven years, says University of Maryland geophysicist Laurent Montesi, an expert in earthquakes and related phenomena.
MEGA-QUAKES: "I am struck by the frequency of large seismic events we have been having since the 2004 Sumatra one," Montesi notes. "This latest event is the sixth largest earthquake on record, and the largest in Japan. Considering the frequent occurrence of earthquakes in that country, this really means something. I find it very interesting how these earthquakes occur in batches, with a large number of mega-quakes in the 1950s and 60s, and over the last 7 years."
Montesi notes that there have been five earthquakes 8.5 Mag. and above since 2004.
TRIGGERING ADDITIONAL SEISMIC ACTIVITY: "Some minor activity is likely to be triggered worldwide by the Japan event as surface waves pass through, especially in geothermally active areas, but this is relatively minor. It is probably over by now," Montesi says.
"The event has probably transferred stress to nearby regions of the Japan subduction zone. It would be possible for the region north of the event (toward Hokkaido) to fail in the next few years. But this is not an exact science. For example, stress near Hokkaido may have been relieved by the magnitude 8.1 event that happened there on 09/15/2003," he says.
"The aftershock for last night's event presents a serious danger: the largest aftershock expected from this event would be big enough to stand as a major earthquake on its own! A M7.1 aftershock did occur approximately 40 minutes after the main shock," he says. "You can be sure there will be a lot of research on these events. For example, I see that a M7.2 earthquake occurred two days ago at roughly the same place as this current event. It may have triggered last night's event! However, I am not aware of anything that would have made this M7.2 earthquake noticeable from any other of that magnitude (worldwide, they occur once a month or so) so it's understandable that no alert for a larger event was issued," Montesi says.
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