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

Abstract

Summary 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.

Ground deformation detection of the greater area of Thessaloniki (Northern Greece) using radar interferometry techniques

“…Due to this the sea barriers that protect the deltaic plain were destroyed and catastrophic floods have occurred several times. (Chatzipetros et al, 2005;Gounaris et al, 2007;Martinod et al, 1997;Stiros, 2001;Stiros and Drakos, 2000). …”

“…Both faulting zones are characterized as active but not as seismic because there is no information connecting the two faults with historical seismic events. Between 1958 and1978, an observed subsidence of about 25 cm (annual average of 12 mm) was observed along a distance of 30 km in the basin from highprecision spirit-levelling results (Stiros and Drakos, 2000). Papazachos et al (2001) studied active crustal deformation for the most active sections of the Mygdonia Basin using the combined stress pattern and corresponding moment-rate tensors.…”

Geodetic evidence for tectonic activity on the Strymon Fault System, northeast Greece

“…Two other major (M>6) 20 th century earthquakes have occurred in the vicinity of the southern SFS (both associated with normal faulting): i) the 1932 M7 Hierissos earthquake (Papazachos 1982;Pavlides and Tranos, 1991) and ii) the 1978 M6.5 Thessaloniki earthquake (Soufleris et al, 1982;Papazachos and Papazachou, 1997;Tranos et al, 2003;Stiros and Drakos, 2000). The epicenters of both of these events are shown in Figure 2.…”

“…The region west of the Strymon River includes also the epicentral area of the 1978 M6.5 Thessaloniki earthquake (Figs. 2&4), the causative fault of which was deduced from elastic dislocation analysis and elevation changes (Stiros and Drakos, 2000;Müller et al, 2013). The sparse distribution of GPS stations around this fault does not, however, permit a precise quantification of the strain that is currently accumulated on this structure.…”

Retrospective Prediction of Macroseismic Intensities Using Strong Ground Motion Simulation: The Case of the 1978 Thessaloniki (Greece) Earthquake (M6.5)

“…The event has been extensively studied (Soufleris and Stewart, 1981;Soufleris et al, 1982;Papazachos and Carydis, 1983;Stiros and Drakos, 2000;Tranos et al, 2003 and references therein). The mainshock was clearly produced by the rupture of a normal fault (see Table I for parameters) along WNW-ESE striking planes (273 -287…”