Tohoku earthquake: a surprise?

By Y. Kagan, D. Jackson. 2011

155 citations recorded by the source corpus.

Abstract We consider three questions related to the 2011 Tohoku mega‐earthquake: (1) Why was the event size so grossly underestimated by Japan’s national hazard map? (2) How should we evaluate the chances of giant earthquakes in subduction zones? (3) What is the repeat time for magnitude 9 earthquakes off the Tohoku coast? The maximum earthquake size is often guessed from the available history of earthquakes, a method known for its significant downward bias. We show that historical magnitudes systematically underestimate this maximum size of future events, but the discrepancy shrinks with time. There are two quantitative methods for estimating the corner magnitude in any region: a statistical analysis of the available earthquake record and the moment conservation principle. However, for individual zones the statistical method is usually ineffective in estimating the maximum magnitude; only the lower limit can be evaluated. The moment conservation technique, which we prefer, matches the tectonic deformation rate to that predicted by earthquakes with a truncated or tapered magnitude–frequency distribution. For subduction zones, the seismic or historical record is insufficient to constrain either the maximum or corner magnitude. However, the moment conservation principle yields consistent estimates: for all the subduction zones the corner magnitude is of the order 9.0–9.7. Moreover, moment conservation indicates that variations in estimated corner magnitude among subduction zones are not statistically significant. Another moment conservation method, applied at a point on a major fault or plate boundary, also suggests that magnitude 9 events are required to explain observed displacement rates at least for the Tohoku area. The global rate of magnitude 9 earthquakes in subduction zones, predicted from statistical analysis of seismicity as well as from moment conservation, is about five per century; five actually happened.

Subfields: Artificial Intelligence, Geophysics

View Paper: https://www.semanticscholar.org/paper/2fc8d4573e926ac14f9c0b0cff8594018acb1d88

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Citations in the corpus

Uniform California Earthquake Rupture Forecast, Version 3 (UCERF3)—The Time‐Independent Model (2014, background): “…and dramatically, exemplified following the UCERF2 publication, by events such as the 2011 M 9 Tohoku earthquake with respect to segmentation (e.g., Kagan and Jackson, 2013), the 2011M 6.3 Christchurch earthquake in terms of spatiotemporal clustering (e.g., Kaiser et al., 2012), and both the 2010…”
Uncertainty modeling and visualization for tsunami hazard and risk mapping: a case study for the 2011 Tohoku earthquake (2016, background): “…dominant earthquake source regions are identified through historical tsunami records or probabilistic tsunami hazard analysis (e.g. Geist and Parsons 2006; Horspool et al. 2014), but their occurrence probabilities and potential earthquake sizes cannot be estimated reliably (Kagan and Jackson 2013).”
The seismic cycle at subduction thrusts: Insights from seismo‐thermo‐mechanical models (2013, background): “1002/2013JB010380 deemed highly improbable for several reasons, including the combination of regional parameters governing subduction dynamics [Stein et al., 2012; Kagan and Jackson, 2013].”