Natural Hazards 27: 61–84, 2002. 61 © 2002 Kluwer Academic Publishers. Printed in the Netherlands. The Fault that Caused the Athens September 1999 Ms = 5.9 Earthquake: Field Observations S. B. PAVLIDES1, G. PAPADOPOULOS2 and A. GANAS2 1Department of Geology, University of Thessaloniki, 54006, Greece E-mail:
[email protected]; 2Geodynamics Institute, National Observatory of Athens, PO Box 20048, 11810 Athens, Greece Received: 18 October 2000; accepted in revised form: 5 November 2001 Abstract. On 7 September 1999 the Athens Metropolitan area (Greece) was hit by a moderate size (Ms = 5.9) earthquake. The severely damaged area is localized in the northwestern suburbs of the ◦ ◦ city, at the foothills of Mt. Parnitha (38.1 N, 23.6 E), about 18 km from the historic centre of Athens. In this paper, we present our results on the surface expression of the seismogenic structure. Methods applied were: field observations, geological mapping, fault geometry and kinematics, evaluation of macroseismic data, interpretation of LANDSAT images, construction of a DEM and application of shading techniques. Aftershock distribution and fault plane solutions were also considered. Our results suggest that the earthquake source is located within the NW-SE trending valley bearing a few outcrops of Neogene- Quaternary sediments across the south foothills of Mt. Parnitha, never known in the past to have been activated by such strong earthquakes. The earthquake occurred along ◦ ◦ ◦ ◦ a 10 km long normal fault, striking N110 –133 and dipping 64 –85 SW, extending from the Fili Fort (4th century BC) in the NNW to the Fili town and then to Ano Liossia, to the SSE.