Rupture Characterization of A Low Magnitude Earthquake of Central Apennines (italy)

This paper describes a detailed study of the rupture mechanism of a M(L) = 3 aftershock of the 1984 Abruzzo (Central Italy) earthquake (M(s) = 5.8). To study the rupture extension, shape and directivity,/the time durations of P and S far-field pulses were analyzed in different directions corresponding to six recording stations. The path corrected far-field displacement P and S pulses at six seismic stations were determined using the empirical Green function method. The fault plane solution has been estimated by joint inversion of P polarities and S polarizations measured on three component records. Finally, we used a method based on the plot of 'isochrons' associated with the observed pulse widths and projected on each nodal plane. The comparison of isochron plots for the two nodal planes suggests a rupture fault plane striking along the Apenninic direction. A weak source directivity up and west-ward on the fault plane was observed. A maximum ruptured surface of 0.4 km2 was estimated assuming a sub-shear rupture process. The estimate of the seismic moment from spectral measurements gives the static stress drop ranging from 1 to 66 bar for the rupture velocity ranging between 0.2 beta and beta, where beta is the shear wave velocity at the source.