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Magnitude-frequency distribution in the European-Mediterranean earthquake regions |
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| Authors: | V Krník K Klíma |
| Institution: | V. Kárník,K. Klíma |
| Abstract: | The European-Mediterranean earthquake catalogue from 1901 to 1985, which comprises uniformly determined magnitudes MS and mB(h ≥ 60 km) of 13300 events, was used in the study of cumulative magnitude-frequency relationships Nc(M) compiled for 75 earthquake regions and 25 larger provinces. In the whole magnitude range observed, the Gutenberg-Richter formula log Nc(M) = a ? bM very rarely fits the cumulative (log Nc, M) distributions. The b-values of log-linear segments of Nc(M) vary regionally from b = 0.7 to b = 1.3; averaging of all values leads to Most distributions pertain to the Mediterranean area (b = 0.86 from the graph for shallow events) and many of them indicate the existence of characteristic earthquakes in accordance with the theoretical single-fault model. Other observed shapes of Nc(M) can be explained by the superposition of populations of different Mmax values or by the presence of swarm-type activity. The observed Nc(M) distributions depend very much on the delineation of earthquake regions i.e. on the number and dimension of seismoactive faults in the investigated region. A premonitory enhancement of medium earthquake activity (M = 4.5–5.5) can be observed only very rarely. |
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