DISS 3.2.GreDaSS: Seismogenic Source GRIS150 - Komotini Fault

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COMMENTS The broader Thrace-GRCS150 shear zone has been described in Mountrakis and Tranos (2004) and Mountrakis et al. (2006) from which most of the principal seismotectonic parameters of this fault (Komotini-GRGG150) have been obtained. Since seismicity is very low in the area and seismological data are scant, the maximum depth (and the width) of the fault was estimated from the seismogenic layer thickness of the adjacent Mygdonia CSS. Mountrakis et al. (2006) associate the fault with the November 6, 1784 earthquake (Mw = 6.7) listed in the earthquake catalogue of Papazachos and Papazachou (1997; 2003). Although in the former edition of the catalogue (1997) the earthquake is located near Meleti village, in the revised 3rd edition (Papazachos and Papazachou, 2003) the epicentre has been relocated 17 km eastwards within the hanging-wall block of the Komotini Fault segment. Accordingly, the proposed magnitude is in better agreement with the length of this fault. Slip per event and Mw are based on analytical and empirical relationships (Kanamori and Anderson, 1975; Hanks and Kanamori, 1979, Wells and Coppersmith, 1994). OPEN QUESTIONS In the frame of the Thrace CSS (GRCS150), is the segment boundary with the nearby Iasmos-GRGG151 fault 'soft' or 'strong'? Could this sharp angular segment boundary safely stop the co-seismic propagation starting from one of the two segments? Another ambiguity concerns the occurrence, the magnitude and the exact location of the 1784 earthquake epicentre, since the only evidence is a macroseismic study in an area not so densely populated during the 18th century. It is noteworthy that the earthquake catalogue of Ambraseys (2009) does not refer at all to this event. SUMMARIES Mountrakis and Tranos (2004); Mountrakis et al. (2006) The authors carried out a geological-morphotectonic mapping at the scale 1:50.000 of the Kavala-Xanthi-Komotini Fault zone (broadly corresponding to the Thrace-GRCS150 of this database). They investigated the geometry, kinematics and fault segmentation of the zone using also seismological data. Within the major shear zone, the Komotini-Sapes Fault (corresponding to the Komotini-GRGG150 fault) is the easternmost segment. It is a 30 km-long, geometrically complex structure consisting ofseveral WNW-ESE and E-W synthetic minor fault strands less than 8 km-long that dip SSW to S at medium to high angles. According to the authors, WNW-ESE-striking branches are cut by, or merge into, E-W trending younger faults. The youngest activity occurs east of Polyanthos village, where a rectilinear fault line [scarp?], a few tens of metres long, with a vertical offset of less than a metre, is observed within the Pliocene-Pleistocene fanglomerate sediments of the hanging-wall. They suggest that this morphotectonic feature is associated with the 1784 (M = 6.7) earthquake reported in the catalogue of Papazachos and Papazachou (2003). Rondoyanni et al. (2004) The authors performed geological mapping and meso-structural analyses of the broader Thrace-GRCS150 shear zone. According to field observations, geometric and dynamic parameters (direction, dip and rake) vary along strike. Within the composite source the Komotini-Aissimi segment (corresponding to the Komotini-GRGG150 fault) outcrops as a more complex structure composed by a group of smaller parallel faults bordering to the northeast the Komotini basin. Two generations of slickenlines on polished fault surfaces have been observed, one associated with oblique-slip movements (dextral and normal components), the other mainly dip-slip normal. Also the alignment and/or displacement of streams and the displacement of recent Quaternary deposits are described and interpreted as morphotectonic evidence of recent activity. Papazachos and Papazachou (2003) There is only a poor description for the November 6, 1784 Kozani earthquake in the catalogue compiled by the authors. No ground effects are reported.