PALAEOSEISMOLOGICAL INVESTIGATION OF THE GYRTONI FAULT (THESSALY, CENTRAL GREECE)

Two paleoseismological trenches were excavated across the Gyrtoni Fault in NE Thessaly and studied in order to understand the recent seismotectonic behavior of this structure. Twenty five fluvial-colluvial sediment and pottery samples from both the upthrown and the downthrown fault blocks were investigated. Optically Stimulated Luminescence (OSL) dating has been applied to date both sedimentary depositspalaeosoils and pottery fragments. Paleoseismological analysis of the two trenches indicates evidence of three surface faulting events in the time span between 1.42 ±0.06 ka and 5.59 ± 0.13 ka. The observed vertical displacement per event of ~0.50 m corresponds to an Mw 6.5 ± 0.1 earthquake. An average fault slip rate of 0.41 ± 0.01 mm/yr and an average recurrence of 1.39 ± 0.14 ka for earthquakes were estimated. The results documented the activity of the fault and since the return period from the most recent event (minimum age 1.42 ± 0.06 ka) has expired, the possibility for reactivation of this active structure in the near future should be included in Seismic Hazard Assessment

Coastal Hazard Vulnerability Assessment Based on Geomorphic, Oceanographic and Demographic Parameters: The Case of the Peloponnese (Southern Greece)

Today low-lying coastal areas around the world are threatened by climate change-related hazards. The identification of highly vulnerable coastal areas is of great importance for the development of coastal management plans. The purpose of this study is to assess the physical and social vulnerability of the Peloponnese (Greece) to coastal hazards. Two indices were estimated: The Coastal Vulnerability Index (CVI) and the Social Vulnerability Index (SVI). CVI allows six physical variablesto be related in a quantitative manner whilethe proposed SVI in this studycontains mainly demographic variables and was calculated for 73 coastal municipal communities. The results reveal that 17.2% of the shoreline (254.8 km) along the western and northwestern coast of the Peloponnese, as well as at the inner Messiniakos and Lakonikos Gulfs, is of high and very high physical vulnerability. High and very high social vulnerabilities characterize communities along the northwestern part of the study area, along the coasts of the Messinian and Cape Malea peninsulas, as well as at the western coast of Saronikos Gulf

Modelling and Mapping Coastal Protection: Adapting an EU-Wide Model to National Specificities

We explore the requirements for adapting coastal protection EU-wide indicators nationally. The aim of this research is threefold: (a) to map coastal protection at the national level; (b) to assess the congruence between the regional and national coastal protection estimates; and (c) to qualitatively assess the congruence of our findings with subnational estimates. We assessed coastal protection capacity, exposure, and demand and adapted them for the coastal zone of Greece. We quantitatively compared our findings with the results of the EU model. Through visual interpretation, we compared national estimates with those for the coastal zone of Peloponnese. Most islands have lower protection capacity than the mainland areas, while the southern part of the country’s coastal zone is the most exposed to natural hazards. Higher coastal protection demand was detected in the country’s largest cities (Athens, Thessaloniki). Areas of attention for management were small and medium islands and urban centres, as they mostly revealed high demand and exposure but the lowest natural capacity. The differences observed in the modelling outputs across scales are attributed to the differences in the demarcation process of the coastal zone, the additional variables considered, the terminology used, and the experts involved. Such national adaptations should be considered in order to build or update EU-wide indicators for coastal protection and beyond, towards a rule-based rather than a one-size-fits-all methodology

Middle–Late Holocene earthquake history of the Gyrtoni Fault, Central Greece: Insight from optically stimulated luminescence (OSL) dating and paleoseismology

The south-dipping Gyrtoni Fault defines the northeastern boundary of the Middle-Late Quaternary Tyrnavos Basin, Central Greece. The recognition and recent tectonic activity of the fault were previously based on mapping, remote sensing analyses and electrical resistivity tomography studies. To understand the Holocene seismotectonic behavior of the Gyrtoni Fault we excavated two paleoseismological trenches. To estimate the timing of past earthquakes using luminescence dating, we obtained twenty five fluvial-colluvial sediment and pottery samples from both the upthrown and the downthrown fault blocks. We applied the Optically Stimulated Luminescence (OSL) dating to coarse grain quartz using the single-aliquot regenerative-dose (SAR) protocol. Our investigations of luminescence characteristics using various tests confirmed the suitability of the material for OSL dating. We found that the estimated OSL ages were internally consistent and agreed well with the available stratigraphical data, archaeological evidence and radiocarbon dates. The performed paleoseismological analysis emphasized the occurrence of three surface faulting events in a time span between 1.42 ± 0.06 ka and 5.59 ± 0.13 ka. Also, we recognized an earlier faulting event (fourth) has been also recognized to be older than 5.59 ± 0.13 ka. The mean throw per event value of 0.50–0.60 m could correspond to a ca. Mw 6.5 earthquake. An average fault slip rate of 0.41 ± 0.01 mm/a and an average recurrence time of 1.39 ± 0.14 ka were also estimated. Our results suggest that the elapsed time from the most recent event (minimum age 1.42 ± 0.06 ka) is comparable with the mean return period

Geomorphic Evolution of the Lilas River Fan Delta (Central Evia Island, Greece)

This paper presents the results of geomorphological investigations carried out on the Lilas River fan delta in central Evia Isl., Greece. A geomorphological map has been prepared using Digital Elevation Model analysis, aerial photos and Google Earth image interpretation, a reliable map of 1846, and extensive fieldwork. The Holocene sequence stratigraphy of the fan delta has been studied based on profiles of seven deep cores drilled by the municipal authorities. Two additional shallow boreholes were drilled with a portable drilling set and collected samples were analyzed using micropaleontological and grain size analysis methods while four sediment samples were dated using optically stimulated luminescence (OSL) techniques. During the early Holocene, most of the fan delta plain was a shallow marine environment. Between 4530 ± 220 and 3600 ± 240 years BP the depositional environment at the area of Nea Lampsakos changed from shallow marine to a lower energy lagoonal one. The main distributary changed its course several times leading to the building and subsequent abandonment of five fan delta lobes, through which the fan delta advanced during the late Holocene. The eastern part of the Kampos abandoned lobe is retreating with a maximum mean rate of −0.94 m/year for the period 1945–2009, whereas the presently active mouth of the river and its immediate surrounds are prograding with a mean rate of about +3.2 m/year

Long-term spatial and temporal shoreline changes of the Evinos River delta, Gulf of Patras, Western Greece

This study deals with the long-term shoreline displacement of the Evinos River delta in Western Greece using various geospatial data sets from different sources. The comparison between the extracted coastlines allowed us to identify segments where the delta progrades and parts of the delta that are being eroded over the periods 1945–1969 and 1969–2015. Coastal area variations giving land losses or gains of the most active sectors of the delta associated with changes in shoreline position were calculated over the periods 1993–2002 and 2002–2018 using Landsat TM satellite images. The results showed that nearly 46% of the Evinos delta is in retreat. Erosion is essentially affecting the eastern deltaic shoreline with retreat rates commonly reaching up to 8 m/yr in places. In addition, the area of the artificially closed pre-1959 mouth of the river has retreated at an average rate of 14 m/yr over the past 57 years. The old natural mouth of the river (depicted in a map of 1885) at Akra Evinou (Cape Evinos) has retreated up to 350 m (5 m/yr) over the last 71 years. West of the active river mouth, mobile elongated features such as sand spits and barriers are formed by deposition of sediment produced by the erosion of the abandoned eastern delta coastline. The main natural cause of the long-term Evinos River delta coastline displacements is the nearshore current activity induced by the dominant incoming wind generated waves. Land loss of the active part of the delta (at rates up to 16,797 m 2/yr) has been recorded over the period 2002–2018. This generalized erosion can be attributed to human activities that include: the construction of a dam in the upper reaches of the catchment that dramatically decreased the suspended sediment concentrations in the delta, the extensive sand and gravel mining in the distributary channel, and a small earth dam constructed at the apex of the delta for irrigation purposes. </p

PALAEOSEISMOLOGICAL INVESTIGATION OF THE GYRTONI FAULT (THESSALY, CENTRAL GREECE)

Two paleoseismological trenches were excavated across the Gyrtoni Fault in NE Thessaly and studied in order to understand the recent seismotectonic behavior of this structure. Twenty five fluvial-colluvial sediment and pottery samples from both the upthrown and the downthrown fault blocks were investigated. Optically Stimulated Luminescence (OSL) dating has been applied to date both sedimentary depositspalaeosoils and pottery fragments. Paleoseismological analysis of the two trenches indicates evidence of three surface faulting events in the time span between 1.42 ±0.06 ka and 5.59 ± 0.13 ka. The observed vertical displacement per event of ~0.50 m corresponds to an Mw 6.5 ± 0.1 earthquake. An average fault slip rate of 0.41 ± 0.01 mm/yr and an average recurrence of 1.39 ± 0.14 ka for earthquakes were estimated. The results documented the activity of the fault and since the return period from the most recent event (minimum age 1.42 ± 0.06 ka) has expired, the possibility for reactivation of this active structure in the near future should be included in Seismic Hazard Assessment