Complex kinematic rupture of the Mw 5.9, 1999 Athens earthquake as revealed by the joint inversion of regional seismological and SAR data.

D. Baumont¹, O. Scotti¹, F. Courboulex² and N. Melis³

Geophys. J Int, 158, 1078-1087

Slip distributions of the moderate magnitude (Mw 5.9), 1999 Athens earthquake, inverted from surface waves and interferometric Synthetic Aperture Radar (SAR) images, show very different characteristics. The robustness analysis proposed in this study, confirms the discrepancy between the well-constrained features of each individual solution. Irrespective of the hypotheses we made (data/modeling errors, low deformation, post- or pre-seismic slip), the joint inversion of the two data sets led to a complex and heterogeneous rupture model. This model is characterized by a short rise time <5 s) slip patch centred on the hypocentre, extending bilaterally up to 4 km depth and do to 17 km and releasing approximately 70 per cent of the total moment. Located further to the WNW and releasing the remaining 30 per cent of the total moment, a long rise time slip patch extends from 8 to 17 km depth. If the short rise time slip patch propagated above and below the brittle zone delineated by the aftershocks, the long rise time slip patch (slow deformation) appears to be mostly confined below the brittle zone. This unified model satisfies the analysis of the seismic and geodetic slip distributions as well as the location of the aftershock sequence and attests to the diversity of the crustal response even for moderate size faults.

1 - IRSN/DEI/SARG/BERSSIN. 60-68 Av. du Général Leclerc, PO Box 17, Fontenay aux Roses 92262, France
2- Géosciences Azur. 250 Av. Albert Einstein. Valbonne 06560, France
3 -NOA-IG. PO Box 20048, Lofos Nymfon. Athens GR-118 10, Greece