THE 1953 EARTHQUAKE IN CEPHALONIA (WESTERN HELLENIC ARC) - COASTAL UPLIFT AND HALOTECTONIC FAULTING

Geomorphological, marine biological and radiometric data in combinatio n with earlier reports reveal that the M(s)=7.2, 1953 Cephalonia earth quake, the most destructive but least studied earthquake in Greece thi s century, was associated with a 0.3-0.7 m quasi-rigid-body uplift and westward tilting of the central part of the island. Another palaeosei smic event, around 1500 yr BP, associated with coastal uplifts was als o identified. Structural data indicate that the 1953 uplift is bounded by two subparallel, east-dipping major reverse faults and corresponds to a piston-like motion. This structurally unusual pattern of seismic deformation is detached from the deformation of the basement (conspic uously a thrust) and different from the long-term deformation pattern of the area; it is probably due to the particularities of salt tectoni cs: a approximately 1500 m thick salt layer acts as a regional decolle ment, while thinner layers are sandwiched between the carbonate thrust sheets that compose the overburden and reduce their friction during f ault movement. This crustal anisotropy is responsible for the observed anomalous attenuation of seismic waves during the 1953 and historical earthquakes. The 1953 seismic surface deformation mimics long-term ha lotectonic patterns, but is not directly indicative of the regional st ress-field, for it reflects uplift-induced stresses only.