GreDaSS_2.0: Seismogenic Source GRCS070 - Amyndeo

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COMMENTS The Amyndeo Composite Source is a large fault zone bordering the northwesternmost margins of Ptolemaida Basin. Many authors have recognized and mapped the zone (Pavlides, 1985; Pavlides and Mountrakis, 1987; Doutsos and Koukouvelas, 1998; Goldsworthy and Jackson, 2000; 2001; Mountrakis et al., 2006; Xanthopoulou, 2006). According to Goldworthy et al. (2002), it consists of two fault segments, the Nymfaeon (GRGG070) and Petron (GRGG071) Faults, respectively. Although the authors suggest a right stepping, overlapping geometry of these two fault segments, in this database a simple geometrical barrier was preferred. Maximum depth is based on the cross-section of the Ptolemaida Basin proposed by Pavlides and Simeakis (1987/1988). Strike is based on geological and morphotectonic mapping from all previous authors. Dip range is according to field measurements (Pavlides, 1985) and the schematic cross section across the major fault zones of Ptolemaida Basin proposed by Pavlides and Simeakis (1987/1988). Rake derives from kinematic indicators measured by Pavlides (1985) and Pavlides and Mountrakis (1987). Taking into account the total length of the zone, assuming that both fault segments can be co-seismically reactivated, and using the empirical relationships of Pavlides and Caputo (2004), a maximum expected magnitude of 6.9 is suggested. OPEN QUESTIONS Although Goldsworthy et al. (2002) suggest a right stepping, partially overlapping fault geometry, there are no strong evidences to support this. A more suitable boundary probably is an angular one according to descriptions and suggestions from other authors (Pavlides, 1985; Pavlides and Mountrakis, 1987; Pavlides and Simeakis, 1987/1988; Xanthopoulou, 2006). SUMMARIES Pavlides (1985) The author conducted a geological-morphotectonic mapping together with meso-structural analyses of the broader Ptolemaida Basin. Based on morphotectonic mapping and geomorphologic considerations, the Nymfaeo and Petron Faults (GRGG070 and GRGG071, respectively) have a total length of approximately 30 km, starting from Petron Lake and ending near to Nymfaeon village. According to field observations and measurements, the fault (Petron) outcrops at the northwestern side of the Petron Lake with N35-45°E strike, 60° dip and and 250 m of visible total vertical displacement. The fault escarpment is not continuous in most of its length and sometimes is covered beneath the Neogene deposits which however show small scale tectonic structures. In other locations the fault forms a zone affecting metamorphic rocks of Mount Vernon and sediments, many of which are of Plio-Pleisocene and Neogene age. The author suggests that there should be high fault activity since Pliocene producing a large displacement represented by the high relief and the high-altitude emplacement of the Pleistocene conglomerates. He also found evidences for late Pleistocene or even Holocene reactivation from the presence of some debris cones, containing also remnants of Red Beds, in Kelli-Ag. Athanasios area, and from the existence of mineral water springs near to Xino Nero and Aetos villages. Pavlides and Mountrakis (1987) The authors carried out a meso-structural analysis in the broader area of the Florina-Ptolemaida Basin, producing a geological-morphotectonic map. They suggest that the geomorphological features of the basin (partitioned into smaller sub-basins, including the local four lakes, separated by ridges) are tectonically controlled mainly by large normal faults, striking NE-SW and reaching a length up to 30 km. The most important are: 1. the Petron-Nymfaeon Fault (corresponding to Petron-GRGG071 and Nymfaeo-GRGG070 Faults of this database, respectively) which strikes N30°E, dips SE and is more than 30 km long, 2. the Vegoritis Fault (corresponding to Vegora-GRGG072 and Vegoritida-GRGG073 Faults of this database) which strikes N40°E, dips to the SE and counts 20 km of length, 3. the Chimaditis-Anargiri Fault (corresponding to Chimaditis-GRGG075 Fault of this database) which strikes N30°E, dips NW and is more than 10 km in length, and 4. the group of parallel NE-SW normal faults of the Mt Vermio-Komnina valley and Ptolemais-Proastio subsidence which extend for over 50 km. The authors suggest that all previous faults are active inherited structures because they cut both the pre-Neogene formations (mainly Mesozoic limestones of the basin margins) and the unconformably overlying Neogene-Quaternary sediments. They also support the recent activity proposal on the well developed tectonically controlled morphology along their strike. After the meso-structural analysis, they conclude that West Macedonia has been under widespread extension divided in at least two phases since Miocene, all related to normal faulting. The older one is the Late Miocene-Pliocene phase with a NE-SW direction of extension and the most recent one is the Quaternary to present phase with a NW-SE direction of extension. Pavlides and Simeakis (1987/1988) The authors performed a seismotectonic investigation in the Ptolemaida Basin. The only available well defined seismic event occurred on July 9, 1984, but according to the authors it related with the Peraea Fault (GRGG074). The shape of the isoseismal contours is elongated into a NE-SW axis matching the direction of the geologically active faults of the area. Doutsos and Koukouvelas (1998) Concerning the northern margin of the basin, the authors suggest a different fault geometry: a northeast trending fault zone consisting of two right stepping segments in a smaller scale, the Petres and Vegoritis segments (corresponding to Amyndeo-GGCS070 and Ptolemaida-GGCS072 Composite Sources of this database, respectively).The authors also investigated the inner part of the Ptolemaida Basin where inside the coal field there are a large number of faults with displacements ranging over several orders of magnitude. The largest population of them belongs to a single data set of normal faults whose direction change slightly from ENE-WSW to E-W. Faults are planar, dipping 60-80°, and show a near tip listric geometry. Goldsworthy and Jackson (2000; 2001) The authors, based on previous studies by Pavlides and Mountrakis (1987), try to investigate the interaction and timing of the parallel and ca. 7 km apart Petron, Vegoritida (GRGG073) and Peraea (GRGG074) Faults. According to their morphotectonic map, the two fault segments of Amyndeo Fault Zone (Nymfaeo and Petron Faults, respectively) are partially overlapped forming a right stepping geometry. Based on geomorphological considerations they suggest that the fault activity of the Petron, Vegoritida and Peraea Faults gradually migrates from NW to SE. Goldsworthy et al. (2002) The authors carried out a morphotectonic investigation in the western part of the Ptolemaida Basin which is tectonically controlled by NE-SW normal faults. They suggest that Xino Nero Fault (corresponding to Nymfaeo Fault-GRGG070 of this database) partially overlaps Petron Fault (GRGG071) in the east and disappears in the rough relief of Mount Verno in the west. Together with the antithetic Chimaditis Fault (GRGG075) they tectonically control the western part of the basin. With a total length of 20-25 km, the fault outcrops in Mesozoic limestone, Neogene sediments, and gneiss. A preserved tilted dip slope within the Neogene deposits of the central footwall block is also observed. The authors suggest that Xino Nero Fault cuts across the southern end of the N-S striking Florina-Bitola Fault. They also imply that this fault system might be continued up to the Konitsa Fault. Atzemoglou et al. (2003) The authors performed a Vertical Electrical Sounding (VES) survey in order to investigate the tectonic structure of the NW part of the Amyndeo Basin. They also used borehole data for correlating the VES results with the lithological formations. From the interpreted results they produced pseudo-2D subsurface resistivity sections, pseudo-3D depth slices for depths ranging from 50 m to 450 m, and a 3-D image of the surveyed area depicting the relative depths of the geological background. According to the authors, the geophysical interpretation suggests that two main fault systems can be identified. The first one, associated with a known tectonic contact described by Pavlides (1985) between schists and marbles, has a NW-SE direction and it appears to be between the Aetos-Valtonera axis and the Pedino village. The second fault has almost a N-S direction (Pedino-Valtonera axis) and it sets the western limit of the bedrock prior to its deepening. However, more important clue for recent tectonic activity is the existence of a localized deepening of the bedrock, which appears to be associated to the formation of the Zazari Lake. This structure is shown in the 3-D image having an almost NE-SW direction and dipping to the SE, following the general fault trending if the broader area. Diamantopoulos and Dimitrakopoulos (2004) The authors carried out a geological and morphotectonic study in order to explore the morphology and the sub-surface structure of the pre-Tertiary basement of Ptolemaida-Kozani graben. According to them, Vegoritis-Ptolemais-Kozani graben represents a composite post-orogenic and active graben, which is separated in a couple of elongated perpendicular grabens, characterized by different stratigraphic evolution and sub-surface morphology. They present a map showing the morphology and the sub-surface structure of the pre-Tertiary basement based on drillings, geophysical and hydrogeological data of PPC (Public Power Corporation). Mountrakis et al. (2006) The authors carried out a morphotectonic mapping and a mesostructural analysis of the Ptolemaida Basin, suggesting two large antithetic boundary fault zones trending NE-SW and many secondary, parallel, synthetic or antithetic ones within the depression. The Nimfeo-Xino Nero-Petra Fault [corresponding to Amyndeo Composite Source (GRCS070) of this database] is the northwesternmost marginal SE dipping zone with a cumulative length of 30 km, delimiting the Neogene and Quaternary sediments against the Alpine basement. According to the authors, the best morphological exposure of the fault occurs between the Nymfaeo and Aetos villages, while in Xino Nero village the Neogene sediments have been depressed by about 100 m. Xanthopoulou (2006) The author conducted a morphotectonic analysis accompanied with geological and morphotectonic mapping for the broader area of the Ptolemaida Basin. Field measurements on the Nymfaeo-Xino Nero-Petron Fault [corresponding to Amyndeo Composite Source (GRCS070) of this database] suggest a strike of N40-50°E a dip of 60°, while after field observations and morphological considerations the author suggests a total length of 30 km. From field observations near Xino Nero and Fanos villages, affected Pleistocene deposits are reported, while in Petron area, travertine formations have also been affected. Several morphotectonic parameters were also used to prove the recent tectonic activity. Some of them imply higher and more recent activity from the NE to the SW part of the Amyndeo Fault Zone.