Source Parameters of Earthquakes Recorded Near the Itoiz Dam (Northern Spain)

We calculate the source parameters and attenuation from earthquakes recorded near the Itoiz dam, from 2004 to 2009, with magnitudes ranging between 1.2 and 5.2. We use a Genetic Algorithm in order to fit the three-component P-wave spectra with the spectral level, corner frequency, and attenuation factor as searching parameters. The obtained moments range from 1.72 x 10(11) to 2.65 x 10(15) Nm, the radii span from 0.09 to 1.00 km, and the stress drops vary from 0.006 to 29.462 MPa. The maximum value for the Q attenuation factor is 794, and the minimum value is 53. We find a good agreement between empirical and theoretical relationships between moment and magnitude. There seems to be a breakdown of self-similarity, but it could be due to the method used. We group the data by means of a Self-Organizing Map and the clusters found are related by their magnitude, and not by other considerations.