Assessing enigmatic boulder deposits in NE Aegean Sea: importance of historical sources as tool to support hydrodynamic equations

Due to their importance in the assessment of coastal hazards, several studies have focused on geomorphological and sedimentological field evidence of catastrophic wave impacts related to historical tsunami events. Among them, many authors used boulder fields as important indicators of past tsunamis, especially in the Mediterranean Sea. The aim of this study was to understand the mechanism of deposition of clusters of large boulders, consisting of beachrock slabs, which were found on the southern coasts of Lesvos Island (NE Aegean Sea). Methods to infer the origin of boulder deposits (tsunami vs. storm wave) are often based on hydrodynamic models even if different environmental complexities are difficult to be incorporated into numerical models. In this study, hydrodynamic equations did not provide unequivocal indication of the mechanism responsible for boulder deposition in the study area. Further analyses, ranging from geomorphologic to seismotectonic data, indicated a tsunami as the most likely cause of displacement of the boulders but still do not allow to totally exclude the extreme storm origin. Additional historical investigations (based on tsunami catalogues, historical photos and aged inhabitants interviews) indicated that the boulders are likely to have been deposited by the tsunami triggered by the 6.7 <i>M</i><sub>s</sub> Chios-Karaburum earthquake of 1949 or, alternatively, by minor effects of the destructive tsunami produced by 1956's Amorgos Island earthquake. Results of this study point out that, at Mediterranean scale, to flank numerical models with the huge amount of the available historical data become a crucial tool in terms of prevention policies related to catastrophic coastal events

Assessing enigmatic boulder deposits in NE Aegean Sea: Importance of historical sources as tool to support hydrodynamic equations

Due to their importance in the assessment of coastal hazards, several studies have focused on geomorphological and sedimentological field evidence of catastrophic wave impacts related to historical tsunami events. Among them, many authors used boulder fields as important indicators of past tsunamis, especially in the Mediterranean Sea. The aim of this study was to understand the mechanism of deposition of clusters of large boulders, consisting of beachrock slabs, which were found on the southern coasts of Lesvos Island (NE Aegean Sea). Methods to infer the origin of boulder deposits (tsunami vs. storm wave) are often based on hydrodynamic models even if different environmental complexities are difficult to be incorporated into numerical models. In this study, hydrodynamic equations did not provide unequivocal indication of the mechanism responsible for boulder deposition in the study area. Further analyses, ranging from geomorphologic to seismotectonic data, indicated a tsunami as the most likely cause of displacement of the boulders but still do not allow to totally exclude the extreme storm origin. Additional historical investigations (based on tsunami catalogues, historical photos and aged inhabitants interviews) indicated that the boulders are likely to have been deposited by the tsunami triggered by the 6.7 M s Chios-Karaburum earthquake of 1949 or, alternatively, by minor effects of the destructive tsunami produced by 1956's Amorgos Island earthquake. Results of this study point out that, at Mediterranean scale, to flank numerical models with the huge amount of the available historical data become a crucial tool in terms of prevention policies related to catastrophic coastal events. © 2012 Author(s). CC Attribution 3.0 License

Arhaeological evidence for seismic activity in Butrinti (SW Albania)and neotectonics of the area

This is a preliminary study of the neotectonics and the historical seismic destruction imprinted on the archaeological site of Butrinti (SW Albania). Two fault sets surround and intersect both the limestone hill with the archaeological site and the area around it. A normal N-S trending fault is located along the NW of Butrinti hill with an observable length of 1 km and a maximum vertical displacement of 3-4m. The southern part of the hill is confined by a steep tectonic scarp, trending E-W to NE-SW, which represent the continuity of the transcurrent (right-lateral strike-slip) fault of Northern Corfu. Fault planes parallel to this fault have been observed inside the archaeological site. The continuous subsidence of part the ancient city, the presence of evaporates diapirs and their continuous vertical movement allows us to conclude that these faults are still active. Cracks crossing special foundation stone elements of archaeological buildings and other types of dislocation were the main criteria to evident seismic damage in this study. The catastrophes of the Hellenistic-Roman theatre of Butrinti and the surrounding monuments dated to the 3rd-4th century AD should be attributed to the seismic activity triggered by the reactivation of these faults during late Roman-early Byzantine time (358 AD). Another seismic event affecting Byzantine monuments is also probable (1153)