Earthquake potential and magnitude limits in southern europe

Seismic Hazard Harmonization in Europe (SHARE) published new seismic hazard maps of Europe in 2013. Seismic source models are the basis for hazard calculations. SHARE constructed three seismic source models based on historical earthquakes and geological fault data. The SHARE source models provided parameters from which magnitude-frequency distributions can be specified for each of 437 seismic source zones covering most of Europe. To evaluate the SHARE seismic source models, we construct an earthquake potential model of Southern Europe using the Global Strain Rate Map released in 2014. Because the individual SHARE area source zones are too small to have sufficient data for accurate estimates, we combine the source zones into five groups according to SHARE’s estimates of maximum magnitude. Using the strain rates, we calculate tectonic moment rates for each group. Then, we infer seismicity rates and probable maximum earthquake magnitudes from the tectonic moment rates. For two groups, the tectonic moment rates are higher than SHARE seismic moment rates; SHARE rates of large earthquakes are lower than those inferred from tectonic moment rates, but higher than those based on historical earthquakes. For another group, the tectonic moment rate is lower than SHARE seismic moment rates; SHARE rates of large earthquakes are higher than those inferred from tectonic moment rate, but lower than what historical data show. For the other two groups, the seismicity rates from tectonic moment rate, historical data, and SHARE models are consistent. For four groups, the maximum magnitudes used by SHARE are fairly consistent with the probable maximum magnitudes inferred from tectonic strain rates. This study demonstrates that: 1) the strain rate data are useful for constraining seismicity rates and magnitude limits; and 2) the SHARE seismic source models fit for the purpose.