Perceptible earthquakes in the broad Aegean area

A probabilistic estimate of seismic hazard can be obtained from the spatial distribution of earthquake sources, their frequency-magnitude distribution and the rate of attenuation of strong ground motion with distance. The authors calculate the earthquake perceptibility, i.e., the annual probability that a particular level of ground shaking will be generated by earthquakes of a particular magnitude, by weighting frequency-magnitude data with the predicted felt area for a given level of ground shaking at a particular magnitude. This provides an earthquake selection criterion that can be used in the seismic-resistant design of non-critical structures. The perceptibility, at a particular value of isoseismal intensity, peak ground acceleration and velocity, is calculated as a function of source magnitude and frequency for the broad Aegean area using local attenuation laws. Frequency-magnitude distributions are used that were previously obtained by combining short-term catalogue data with tectonic moment rate data for 14 tectonic zones in Greece with sufficient earthquake data and where contemporary strain rates are available from satellite data. Many of the zones show a "characteristic earthquake" distribution, with the most perceptible earthquake equal to the maximum magnitude earthquake, but a relatively flat perceptibility between magnitudes 6 and 7. The maximum perceptible magnitude is in the fastest-deforming region in the middle of the Aegean sea and tends to be systematically low in the western part of the Aegean Sea in comparison with the eastern part. The tectonic data strongly constrain the long-term recurrence rates and lead to low error estimates (plus or minus 0.2) in the most perceptible magnitudes.