DISS 3.2.GreDaSS: Seismogenic Source GRCS077 - Komanos

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COMMENTS The Komanos Composite Source is the southernmost fault zone that bounds the southeastern margin of the Ptolemaida Basin and consists of two major visible fault segments: the western Proastio (GRIS078) and the eastern Mesovouni (GRIS077) Faults. There is a 7 km gap of morphological continuity between the two segments, although the possibility of continuation under the sediments with a small change in strike exists. The neotectonic regime of the area has been investigated by many authors. Most of the geometric and kinematic parameters (strike, dip, rake) are obtained from Pavlides (1985), Pavlides and Mountrakis (1987), Mountrakis et al. (2006) and Xanthopoulou (2006). Concerning the dipping angle, the schematic profile from Pavlides and Simeakis (1987/1988) has been also taken into account. Maximum depth is based on the cross-section of the Ptolemaida Basin proposed by Pavlides and Simeakis (1987/1988). There are no significant earthquakes known in the region of Ptolemaida Basin. However, according to the earthquake catalogue of Papazachos et al. (2009), low-magnitude events (<5) rather frequently occur. A moderate earthquake occurred on July 9, 1984 with Ms = 5.2 (Pavlides and Simeakis, 1987/1988) which is probably attributed to the antithetic Peraea Fault (GRIS074). Although the total length of the zone is ca. 35 km, only one segment can probably be reactivated for each time. In this case, the largest structure of the Komanos CS is the Mesovouni Fault which is 17 km long. Using the empirical relationships of Pavlides and Caputo (2004), a maximum expected magnitude of 6.6 (± 0.5) is suggested. OPEN QUESTIONS There are no data for the type of connection between the two fault segments of this CS. SUMMARIES Pavlides (1985) The author investigated the whole Ptolemaida Basin. He carried out a neotectonic mapping of the broader area as well as structural analyses. At the southeastern margin of the basin, the Proastio and Mesovouni ISs are depicted forming a larger fault zone corresponding to the Komanos CS of this database. The lignite mines offer a very good exposure of post-Pliocene, NE-SW striking faults cutting the thick Neogene deposits and the lignite strata, forming a large tectonic horst subduing the deposits northwards and southwards of the Komanos village. One group of parallel faults that dips northwards belongs to the southwestern part of the Komanos CS. Measurements on one of the major striated fault surfaces demonstrate 40° strike, 70° dip towards NW, 80°-85° pitch and 50 m displacement. Smaller synthetic microstructures along the fault affecting Quaternary conglomerates indicate a very recent activity. A series of blind, parallel faults located basinwards with a cumulative displacement of 300-400 m are discovered from boreholes. A secondary fault group of NW-SE trending faults is also observed. At the northeastern part of the zone, a NW dipping structure (corresponding to the Mesovouni IS of this database) marginal to the southeastern part of the Komnina Valley is discovered from boreholes. An antithetic fault on the opposite side of the valley is also observed. Displacements vary from 20 to 40 m, while displacements of 70 m are rarely observed. Diamantopoulos (2006) The author proposed a structural synthesis based on data obtained by field analysis, drilling and geophysical investigations. The NE-SW trending Komanos horst, which divides the Vegoritis–Ptolemais and Ptolemais–Kozani sub-basins, is considered as one of the main morphotectonic units of the investigated area. According to the author, this horst represents a pre-existing structure which was reactivated during Plio-Quaternary times. At the northern side of the Komanos horst, in the Vegoritis–Ptolemais sub-basin, a W-NW tilting of the sedimentary fill is suggested and it is interpreted as a result of an approximately NW-SE trending axis throughout the basin. The proposed deformation pattern is that intra-plate deformation of Western Macedonia is dominated by progressive shear strain, where the principal axes of extension and compression, transtension and transpression are controlled by progressive sinistral simple shear. Mountrakis et al. (2006) According to the authors the 30 km-long Proastio-Komnina-Mesovouni Fault Zone (corresponding to Komanos CS of this database) bounds the southeastern margin of the Ptolemaida Basin and consists of two sub-parallel fault segments: the 10 km-long Proastio Fault (GRGG078) and the 20 km-long Mesovouni Fault (GRGG077). Both fault segments dip steeply NW. The Proastio fault mainly affects the Upper Villafranghian Proastion Formation, consisting of conglomerates, and forms a rectilinear fault scarp within these sediments. The Mesovouni fault cuts the Triassic-Jurassic Pelagonian marbles and forms a narrow valley filled with Quaternary sediments. The latest formed slickenlines observed on the fault’s outcrops indicate an extension stress field of a NW-SE direction. Xanthopoulou (2006) The author carried out a morphotectonic investigation of the Ptolemaida Basin. At the southern part the author investigates the Proastio (GRIS078) and Mesovouni (GRIS077) Faults which are segments of the Komanos CS of this database. Taking into account the age of the sediments affected (Pleistocene) and some morphometric characteristics, the author suggests that both faults are active.