THE NUCLEATION AND RUPTURE PROCESS OF THE 1981 GULF OF CORINTH EARTHQUAKES FROM DECONVOLVED BROAD-BAND DATA

Source parameters of the largest three normal faulting earthquakes (M(s)6.6, 6.3, 6.4), in the 1981 Gulf of Corinth (Greece) sequence are determined using deconvolved broad-band data (recorded by arrays and single stations) and a 2-D finite source model. Such a model enables the spatial extent, rupture velocity and stress drop of the earthquakes to be determined and geological observations of surface slip can be included as a further constraint on the waveform modelling. All three earthquakes were shallow (<10 km) with low stress drops (<30 bars), and exhibited source complexity. The correspondence between the complexity of the earthquake sources and that of the mapped fault breaks implies that the segmentation of surface faulting in Greece is representative of faulting at depth. Tiny initial pulses which correlate across the arrays are seen in the seismograms from the Gulf of Corinth earthquakes at most stations. These initial subevents (<1 per cent of the total moment) are interpreted as the breaking of small asperities which initiated the main rupture and are used to constrain the attenuation correction (t(*) = 0.2 s).