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Whole Earth high-resolution earthquake forecasts

Yan Y. Kagan, & David D. Jackson

Published 2012, SCEC Contribution #1634

Since 1977 we have developed statistical short- and long-term earthquake forecasts to predict earthquake rate per unit area, time, and magnitude. The forecasts are based on smoothed maps of past seismicity and assume spatial and temporal clustering. Our new program forecasts earthquakes on a 0.1 degrees grid for a global region 90N--90S latitude. We use the PDE catalog that reports many smaller quakes (M>=5.0). For the long-term forecast we test two types of smoothing kernels based on the power-law and on the spherical Fisher distribution. The effective width of these kernels is much larger than the cell size, thus the map discretization effects are insignificant. We employ adaptive kernel smoothing which improves our forecast both in seismically quiet and active areas. Our forecasts can be tested within a relatively short time period since smaller events occur with greater frequency. The forecast efficiency can be measured by likelihood scores expressed as the average probability gains per earthquake compared to spatially or temporally uniform Poisson distribution. Another method uses the error diagram to display the forecasted point density and the point events. Our short-term forecasts also assume temporal clustering described by a variant of Omori's law. Like the long-term forecast, the short-term version is expressed as a rate density in location, magnitude, and time. Any forecast with a given lower magnitude threshold can be recalculated, using the tapered Gutenberg-Richter relation, to larger earthquakes with the maximum (corner) magnitude determined for appropriate tectonic zones.

Kagan, Y. Y., & Jackson, D. D. (2012). Whole Earth high-resolution earthquake forecasts. Geophysical Journal International, 190(1), 677-686. doi: 10.1111/j.1365-246X.2012.05521.x.