ALBERT

Description: During World War II, future Nobel Prize winner Kenneth Arrow served as a military weather forecaster. "My colleagues had the responsibility of preparing long-range weather forecasts, i.e., for the following month," he wrote. "The statisticians among us subjected these forecasts to verification and found they differed in no way from chance. The forecasters themselves were convinced and requested that the forecasts be discontinued. The reply read approximately like this: `The commanding general is well aware that the forecasts are no good. However, he needs them for planning purposes.'" (Gardner 2010). Seismologists often encounter a similar situation when developing earthquake hazard maps, which ideally describe the level of earthquake hazards in a region and provide a scientific foundation for earthquake preparation and mitigation. However, in recent years many large and destructive earthquakes have occurred in places mapped as having relatively low hazard (Kerr 2011). A striking example is the March 2011 M 9.1 earthquake off Tohoku, Japan, which occurred in an area shown by the Japanese national earthquake hazard map as one of relatively low hazard. Figure 1, from Geller (2011), illustrates his point that ...in recent years many large and destructive earthquakes have occurred in places mapped as having relatively low hazard... The regions assessed as most dangerous are the zones of three hypothetical "scenario earthquakes" (Tokai, Tonankai, and Nankai; see map). However, since 1979, earthquakes that caused 10 or more fatalities in Japan actually occurred in places assigned a relatively low probability. This discrepancy—the latest in a string of negative results for the characteristic earthquake model and its cousin, the seismic-gap model—strongly suggests that the hazard map and the methods used to produce it are flawed and should be discarded. Similar discrepancies have occurred around the world. The 2008 Wenchuan earthquake...