Sunday, May 22, 2011

An anomalous event?

Three fascinating studies measuring the diplacement of land and energy of the recent earthquake in Japan have been published by Science Magazine.  The research suggests an earthquake unusual if not anomalous in intensity, energy, and displacement. Science Magazine is making the news and research coverage of the quake free for all visitors.
"With such a limited perspective on the past release and the current buildup of strain, a magnitude-9 quake caught researchers by surprise. Learning that most of the March megaquake’s slip was concentrated on two segments makes scientists more worried about other faults around the Pacific. “If you can get a 9 that is this compact,” Wald says, “it increases the number of places you can [fit in] a 9 where you may not have expected one." "  from New Work Reinforces Megaquake’s Harsh Lessons in Geoscience 
"That the 2011 event produced approximately 50 m of slip up-dip of the historical Miyagi M7+ events is roughly consistent with a 500 to 1,000 year potential slip accumulation period. However, there is no basis on which to assume that the aforementioned interval of 1,100 years is representative of the recurrence interval of great earthquakes in this segment—it could be shorter by a factor of two and still be consistent with the surface displacement budget and the peak slip inferred in this recent earthquake."  from The 2011 Magnitude 9.0 Tohoku-Oki Earthquake: Mosaicking the Megathrust from Seconds to Centuries
"We find a mainshock radiated energy ES = 9.1 × 10^18 J, averaged over all stations and all choices of eGf....Nevertheless,  our estimate is about twice as large as the 5.1 × 10^17 J determined by the USGS."  from "Shallow Dynamic Overshoot and Energetic Deep Rupture in the 2011 Mw 9.0 TohokuOki Earthquake"
"The focal region inferred from the distribution of aftershocks stretches about 500 km long and 200 km wide offshore (1)... In particular, at MYGI near the epicenter, we detected a huge  co-seismic displacement of about 24 m toward ESE and about 3 m upward."  from Displacement Above the Hypocenter of the 2011 Tohoku-Oki Earthquake 

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