Karl, from AmericanInTokyo's first hand report, and from the ongoing research at Japan's Earthquake Prediction Research Center (EPRC) and elsewhere, it then becomes easy to believe that this earthquake was predicted prior to its occurrence.
Prediction Capability of Large Earthquakes
There is a persistent idea that earthquake phenomena in general are explained by the self-organized criticality, and that they are unpredictable catastrophes. This persistent idea is a hypothesis to be checked rigorously in scientific terms. Our primary concern is whether large earthquakes that are so damaging to humankind are predictable or not. To what extent the above idea is correct and whether or not the self-organized criticality is applicable to large earthquakes, therefore, need to be closely checked scientifically. We point out that the above-mentioned hypothesis is not applicable to large earthquakes, and suggest below that large earthquakes are predictable.
A large earthquake occurs along a preexisting large-scale fault. A heterogeneous fault evolves gradually with the repetition of earthquake slip on the fault in a given tectonic setting, and this makes a matured fault depart from the self-similarity. A large earthquake tends to occur along such a matured, large-scale fault. This may be one reason why the self-organized criticality is not applicable to large earthquakes.
A large earthquake can take place, only after a large amount of the elastic strain energy has been stored in the medium surrounding the fault. The elastic strain energy is accumulated with tectonic stress buildup after the earthquake occurrence. However, a long time period is needed for the strain energy to be stored again up to a critical level which has a potential to produce a next large earthquake on the same fault. This may be another reason why the self-organized criticality is not applicable to large earthquakes.
The seismogenic layer includes characteristic lengths of various scales departed from the self-similarity. There are a range of characteristic length scales between the fault zone thickness and the depth of seismogenic layer. For instance, the depth of seismogenic layer, fault segment size, fault zone thickness, barrier or asperity size will be candidates of representative characteristic scales. The size of an earthquake is virtually prescribed by some of these characteristic length scales in a given tectonic setting. It is widely recognized that some physical quantities inherent in the rupture are size-scale dependent, and these size-scale dependent physical quantities are also prescribed by such a characteristic length of smaller scale.
Rupture phenomena, including the earthquake rupture, are inherently scale-dependent, and the scale dependency is of critical importance for physical modeling of the earthquake nucleation, and eventual modeling for earthquake prediction. Recent studies show that a large earthquake is prescribed by a large characteristic length scale, while a small earthquake is prescribed by a small characteristic length scale, suggesting that large earthquakes are predictable.
Prediction Capability of Large Earthquakes
Also see:
Structural inhomogeneities and physical properties of seismogenic layer and fault zone