Geodetic constraints on the fault pattern of the 1978 Thessaloniki (Northern Greece) earthquake (Ms = 6.4)

Abstract

Repeated measurement of a 110 km long, high-precision spirit-levelling traverse indicates that between 1958 and 1978 about 25 cm of subsidence occurred along a distance of 30 km in the Mygdonian Quaternary graben, near Thessaloniki, northern Greece. Observed displacements are significant against random and systematic errors, and most are unrelated to near-surface effects and can be assigned to the 1978 Thessaloniki destructive earthquakes. The available data do not permit a formal inversion, but an elastic dislocation analysis indicates that the main shock of the seismic sequence (Ms = 6.4) was probably associated with a NE-dipping, WNW-trending, blind normal fault marking the southwestern margin of the Mygdonian graben, in agreement with seismological and structural data. There also exists evidence for incipient faulting in the central-southern part of the Mygdonian graben.