ALBERT

Notes: Pavliani is an area of high microseismicity in northern central Greece. There is no evidence in the historical record of large damaging earthquakes in this area since at least 600 BC. We examine contemporary crustal deformation in this area using microearthquake data recorded during 1983–84 by the Volos seismic network, principally, and to a lesser extent by the Patras seismic network.The microseismicity (1–4.6 ML) defines an approximately vertical fault zone trending WSW-ENE, of 55 km length and 25 km depth. the fault-plane solution for the 4.6 ML earthquake shows a strike consistent with the trend of the microseismicity zone, and an extension direction consistent with many large earthquakes in central Greece associated with the extensional greater Aegean. Spectra of the microearthquakes are estimated using P waves obtained by selective windowing designed to exclude other P phases from the coda; seismic moments in the range 1–95 x 1012 N m are obtained, accompanied by estimates of seismotectonic source parameters, including source radii, average stress drop and average coseismic slip. of prime utility is an excellent correlation found between seismic moment and magnitude, and with coseismic slip. This allows heterogeneity in the distribution of individual microearthquake source parameters to be mapped onto the vertical fault-zone plane and the history of coseismic deformation for the whole seismicity observed during 1983–84 to be examined using cumulative slip and moment-release rate. Peaks of high moment-release rate occur in the east and centre of the fault zone. That in the east is dominated by a few large moment-release events; that in the centre by a large number of small events. Both moment-release-rate peaks, despite their different component seismicity, are associated with high cumulative coseismic slip. Only the eastern peak is also associated with high stress drop; it is also shallower, and therefore any surficial interaction is less likely to be attenuated. the surface projection of this peak is within 3 km of a mapped normal fault coincident with an Alpine thrust front delineated by a major scarp of Mesozoic limestone. Surface evidence of recent movement on this normal fault is only slight. Friable fault gouge is seen at a few localities. Displacement could not be determined because the limestone surfaces are deeply weathered and lack kinematic indicators. However, considering the whole fault zone as a cohesive entity, and using a Brune estimate of slip at the current moment-release rate throughout the present extensional tectonic regime, suggests a total vertical displacement of order 175 m, similar to the elevation of the scarp.

Notes: The Patras area lies in the western part of central Greece. It is an area characterized by high seismicity and complex neotectonics. Several devastating earthquakes have occurred in the region since 600 BC. Contemporary crustal deformation is examined in this area using microearthquake data recorded over a lengthy period, during 1983–84, by the Patras Seismic Network, principally, and to a lesser extent by the Volos Seismic Network.The microseismicity (1.8–3.9 ML) defines a zone deepening to the NE, which justifies a possible extension of the Gulf of Corinth major graben towards the Trikhonis Lake to the NW.Spectra of 108 well-located microearthquakes are estimated, using P-waves obtained by selective windowing designed to include only the P-phase; seismic moments in the range 0.3–45.7 × 1012 Nm are obtained, accompanied by estimates of seismotectonic source parameters including source radii, average stress drop and average coseismic slip.Poor correlation is found between seismic moment and magnitude, and the likely reason is the complex nature of the neotectonic regime existing in the area.Two zones differing in crustal deformation characteristics are observed. The Corinth-Trikhonis zone reveals two sets of characteristic faults. The first set is represented by microearthquakes showing distinctive and relatively higher seismic moments in conjunction with lower stress drops and seismic slips. This set of faults shows greater source radius than the second set, and therefore the faults are longer. The second set is characterized by an almost constant source radius within the range of uncertainty, and a wide range of seismic moments, stress drops and seismic slips. The Rio zone is characterized by low seismic slip, stress drop and fault radii, with the exception of the locality south of the city of Patras, where relatively higher seismic slip, stress drop and fault radius are observed.