SW Peloponnese Research Articles

Sedimentological, Geochemical, and Environmental Assessment in an Eastern Mediterranean, Stressed Coastal Setting: The Gialova Lagoon, SW Peloponnese, Greece

This study describes the prevalent sedimentological and geochemical patterns and investigates the environmental status of the bottom of Gialova lagoon, a highly vulnerable coastal site of the EU’s Natura 2000 network. For this task, lithological, geochemical, and microfaunal analyses of sediment samples were combined with a high-resolution bathymetric survey. Potential pollution was determined using geochemical-based (EF, I-geo, and PLI) and faunal (Foram-AMBI) indices. We find that sedimentation is mainly controlled by the bottom morphology, hydrodynamic variations, and biogenic productivity of the lagoon. The application of the multivariate factor analysis technique revealed four dominant factors explaining the geochemical processes occurring in the lagoon. The first factor, namely “terrigenous aluminosilicates associated with Corg vs. autochthonous biogenic carbonates”, discriminates the deposition of detrital sediments, related to the high adsorption of heavy metals—versus bioclastic sediments. The “sulfides” factor represents an anoxic phase of the lagoon floor, whereas the “Mn-oxyhydroxides” factor indicates increased manganese content with several compounded trace elements. The “phosphate” factor reveals multiple sources of phosphorus in the lagoon. The lagoon bottom shows negligible to minor contamination in heavy metals, except Mo and Pb, which induce moderate pollution levels. The maximum contamination and environmental stress concern two small-sized, shallow basins within the lagoon.

3D Laser Scanning and UAVs in cultural heritage: The case of Old Navarino castle in Pylos, Greece

The archaeological site of Palaiokastro (Old Navarino castle), is located in Messenia on the Coryphasium peninsula, at the southern end of the beach of Voidokoilia in the Navarino Bay, SW Peloponnese. Palaiokastro was built during Frankish rule of the Peloponnese, in the 13th century, over the classical Acropolis of Pylos.The aim of this study is the initial documentation of the current situation of the medieval castle of Palaiokastro applying innovative technology including terrestrial laser scanner (TLS) and unmanned aerial vehicles (UAVs). TLS and UAV photogrammetry have been used in an integrated design to rapidly facilitate the acquisition of the whole gate, eliminating all possible occlusions. TLS was exploited for the acquisition of the facades while the UAV was used to capture the top view of castle gate. The recent improvement of the post-processing algorithms provides us with the ability to implement fusion methods of TLS and UAV models and also deliver an accurate 3D model of the whole gate.The combination of photogrammetry from the UAV with the data of the terrestrial laser scanner was used in order to give us a multitude of products such as textured 3D model, orthophotos, 2D floor plans, elevations and sections which are necessary for the complete and accurate geometric documentation of the current situation of the Southwest gate of Palaiokastro Castle. The various products mentioned assist in the better management of the study data and identification of the different construction phases of the South Gate.

Quaternary Evolutionary Stages of Selinitsa Cave (SW Peloponnese, Greece) Reveal Sea-Level Changes Based on 3D Scanning, Geomorphological, Biological, and Sedimentological Indicators

Significant evolutionary stages of Selinitsa Cave (SW Peloponnese, Greece) were revealed by 3D mapping, as well as geomorphological study of the cave and the nearby landscape. Four marine terraces were identified in the area of the coastal cave at 6, 10.7, 16.6, and 30–32 m above sea level (asl), with the terrace at 16.6 m representing Marine Isotope Stage (MIS) 5. The widest karstified space of Selinitsa Cave clusters between 15.73 and 18.05 m above sea level (asl), with the peak lying at 16.4 m asl, corresponding to the level where the phreatic/epiphreatic zone was stable for a sufficient period of time. A tidal notch at 16.4 m asl at the cave entrance is correlated to the marine terrace at 16.6 m. Both features correspond to the sea-level stand at which intense karstification occurred. The tidal notch bears a horizontal arrangement of Lithophaga borings at the vertex. Sedimentological investigation of the Selinitsa fine-grained deposit revealed the paleohydrologic regime of the cave. It is characterized by “slack-water” facies, indicating very low water flow speeds, whereas the thickness of the deposit points to stable hydrological conditions for prolonged periods. The cave sediment height of 18.8 m asl indicates a flooding level higher than sea level. The overlying Plattenkalk flysch is most probably the major source of detritus, and the predominance of authigenic dolomite (>98% modal in the carbonate fraction) indicates a hyposaline environment related to mixing of sea water with percolating fresh water. The approach of this study shows the significance of 3D mapping, bio-geo-Relative Sea Level (RSL) indicators, and sedimentology in deciphering the paleogeographic evolution of coastal karstic systems and subsequently defining the paleoclimate regime of coastal areas in Greece and the eastern Mediterranean during the Late Quaternary.

Non-planarity, scale-dependent roughness and kinematic properties of the Pidima active normal fault scarp (Messinia, Greece) using high-resolution terrestrial LiDAR data

Terrestrial LiDAR (TLS), photogrammetric and field data were collected during the years 2014, 2015 and 2017, at a 20-m long limestone scarp locality along the N–S striking, 70° west-dipping, active Pidima fault (Messinia, SW Peloponnese, Greece). This locality presents an artificially exhumed portion of an active fault plane, thus providing a unique opportunity to study kinematics and limestone scarp morphology (including its curvature and roughness). The survey of 2015 offered a high-density point cloud of the fault scarp with 6-mm working resolution, creating a very close to real life representation 3D model. We found that scarp geometry is non-planar with increasing convexity up-dip and increasing northwesterly dip-directions from north towards south, along strike. Non-planarity is also recorded from the morphological data along strike with the appearance of several, slip-parallel troughs and ridges with a mean distance (half-wavelength) of 0.75 m. The fault-plane roughness (absolute values) is scale dependent. The roughness configuration attains a slip-parallel pattern for observation scales above 1-cm. At observations scales less than 1-cm a slip-normal pattern is weakly visible. The obtained TLS results agree with field data (manual compass measurements) and macroscopic observations. We infer an earthquake magnitude of 6.2 ± 0.2 for the last event along the Pidima fault based on the measured thickness of the smooth stripe that was imaged by t-LiDAR along the non-exhumed surface of the scarp.

Environmental aspects of ancient city planning: a pilot study on Ancient Thouria in the Peloponnese, Greece

ABSTRACT In this paper environmental, topographic and geological data of the Classical till Roman Times thriving city of Ancient Thouria situated in Messenia, SW Peloponnese, Greece are presented in context to their archaeological interpretation of the study area’s landscape and usage. Using environmental and geographic factors in collaboration with soil characterization, a preliminary spatial analysis was conducted, aiming at the archaeological interpretation of parameters such as water availability, weather conditions, topography, settlement accessibility and land fertility, taking under account analytical data of soil samples retrieved from a section of an ongoing excavation. The study was conducted using a digital elevation model of the area that enabled the examination of the criteria of watershed, slope, aspect and visibility and assisted X-ray Fluorescence analysis of soil samples from the Asklepieion excavated area thus highlighting the contribution of spatial and in situ analysis to archaeology.

Climate changes in the Eastern Mediterranean over the last 5000 years and their links to the high-latitude atmospheric patterns and Asian monsoons

Abstract This research aims to improve the knowledge of the mid to late Holocene climate changes and the underlying drivers in the eastern Mediterranean. We focus on the Peloponnese peninsula, SW Greece, characterized by a W-E rainfall/temperature gradient and a strong climate-sensitivity to shifts in the large-scale atmospheric patterns. A radiocarbon-dated sediment core, taken from the ancient Lake Lerna, a former lake in NE Peloponnese, was analyzed for distribution and hydrogen isotope (δD) composition of n-alkanes and bulk organic geochemistry (δ13C, TOC). The predominantly macrophyte (submerged/floating)-derived δD23 profile exhibits the largest long-term fluctuation in the record and co-varies with δD of long-chain n-alkanes providing evidence for precipitation and temperature changes over the last 5000 years. The Lerna δD23 signal is sometimes in agreement with other n-alkane δD records from SW Peloponnese indicating wetter conditions in the peninsula at ca 5000–4600, ca 4500–4100, ca 3000–2600 (more unstable in SW) and after ca 700 cal BP with drier periods at ca 4100–3900 and ca 1000–700 cal BP. Conversely, a NE-SW climate see-saw is revealed at ca 4600–4500, ca 3200, ca 2600–1800, and ca 1200–1000 cal BP when the δD23 Lerna exhibits more positive trends (drier in NE) with a reversal at ca 3900–3300, ca 3200–3000 and ca 1800–1300 cal BP. These opposing and sometimes similar signals between NE and SW Peloponnese can be explained by the relative dominance of high-latitude atmospheric patterns over the peninsula. A similar signal would be expected when the North Atlantic Oscillation (NAO) exerts the main control with NAO (+) creating conditions of reduced moisture. The dipole pattern is likely driven by shifts in North Sea–Caspian Atmospheric pattern (NCP), which account for the present-day regional climate variability with NCP (+) leading to wetter and colder conditions in NE Peloponnese. The Asian monsoonal system likely has an additional impact on the δD variabilities through influencing the summer temperatures. There is a consistency between the Peloponnesian δD signals and monsoonal records after ca 4000 cal BP confirming the actualistic models. Strong monsoonal periods coincide with cooler summers (lower δD values) in Lerna, due to the northerly winds, the Etesians. On the contrary, SW Peloponnese is dominated by warmer conditions during the same periods as the area is located on the lee side of the mountain and highly influenced by the adiabatic warming associated with the subsidence over the Eastern Mediterranean.

Eastern Mediterranean hydroclimate reconstruction over the last 3600 years based on sedimentary n-alkanes, their carbon and hydrogen isotope composition and XRF data from the Gialova Lagoon, SW Greece

Understanding past hydroclimate variability and related drivers is essential to improve climate forecasting capabilities especially in areas with high climatic sensitivity, such as the Mediterranean. This can be achieved by using a broad spectrum of high resolution, multiple proxy records which can also allow us to assess linkages between regional hydroclimate variability and shifts in the large-scale atmospheric patterns. Here, we present a multiproxy reconstruction of the central-eastern Mediterranean hydroclimate changes over the last 3600 years based on a sediment core from the Gialova Lagoon, a shallow coastal ecosystem in SW Peloponnese, Greece. Our combined dataset consists of the distribution and compound-specific carbon and hydrogen isotope (δ13C and δD) composition of n-alkanes, bulk organic matter properties and X-ray fluorescence (XRF) core scanning data. This approach was complemented with a semi-quantitative analysis of plant remains in the core. The results indicate a high contribution of local aquatic vegetation to organic matter. Large δ13C variations in predominantly aquatic plant-derived mid-chain alkanes (C23-25) mainly reflect changes in the aquatic plant abundance and their carbon source. Our data suggest that higher δ13C23-25 values (up to −19‰) largely correspond to expansion of aquatic vegetation during wet and/or cold periods causing carbon-limiting conditions in the water and assimilation of isotopically-enriched bicarbonate by the plants. The δD records of the individual n-alkanes (C17 to C31) exhibit a nearly identical pattern to each other, which implies that they all reflect changes in the source water isotope composition, driven by hydroclimate variability. In addition, the δD profiles are consistent with the XRF data with both proxies being driven by a common hydroclimate signal. We observe two major shifts from dry and/or warm periods at ca 3600-3000 cal BP and ca 1700-1300 cal BP to wet and/or cold episodes at ca 3000-2700 cal BP and ca 1300-900 cal BP. The period ca 700-200 cal BP is the wettest and/or coldest in our record and coeval with the Little Ice Age. The climatic fluctuation reported in this study can be explained by the relative dominance of high-latitude (e.g. North Atlantic Oscillation during winters) and the low-latitude atmospheric patterns (Intertropical convergence zone, Subtropical High and the effects of Asian monsoons during summers) which suggests an Atlantic-Mediterranean-Monsoon climate link in this area for the late Holocene.

Biomarker hydrogen isotope composition (δD) as proxy for Holocene hydroclimatic change and seismic activity in SW Peloponnese, Greece

ABSTRACTWe present a 6000‐year‐long record tracing hydroclimate changes in SW Greece, based on hydrogen isotope composition of aquatic plant‐derived n‐C23 alkanes (δDC23) in a sediment core from the Messenian plain, Peloponnese. The δDC23 record co‐varies with other eastern Mediterranean records, suggesting relatively wetter conditions c. 6–4.5 ka, followed by progressively drier conditions leading up to maximum aridity c. 2.8 ka. This arid phase was interrupted by a shift in δDC23 between 3.3 and 3.1 ka inferring wetter conditions and/or tentative responses to anthropogenic water regulating activities during the Late Bronze Age. After 2.7 ka, a return to more humid conditions was followed by increased dryness and stronger seasonality contrasts from c. 2.0 ka. The δDC23 record shows three short‐lived excursions (5.7, 5.3, 2.8 ka), where isotope values dropped by >20‰ and immediately stabilized again. The events were paralleled by abrupt increases in sedimentation rates. We hypothesize that the isotopic shifts represent a response to mixing of ground water systems during tectonic events, followed by sealing of seismically derived cracks in the active fault. The outcome of the study is promising for future expansion of isotope‐based proxies on sediments in the region, to reconstruct both hydroclimate and past seismic activity.

Middle to late Holocene palaeoenvironmental study of Gialova Lagoon, SW Peloponnese, Greece

The coastal areas of Eastern Mediterranean have long been the subject of research, due to their rapid geomorphological changes, but also because of their archaeological interest. Our study is focused on a shallow coastal lagoon of Peloponnese, Gialova Lagoon, which for several years has attracted the scientific interest of archaeologists, geomorphologists as well as sedimentologists. Gialova lagoon is located near the ancient city of Pylos, the kingdom of king Nestor during the Mycenaean period (1600–1100 BC). The objectives of this study are: (a) to reconstruct the middle to late Holocene depositional environments of the lagoon and (b) to correlate our data to already existing publications, in order to shed new light on the Holocene evolution of the lagoon and the associated coastal palaeoenvironmental changes. An 8 m deep vibracore was drilled and a multi proxy analysis was carried out on the sediment sequence, including sedimentological (grain size analysis and moment measures, total organic carbon – TOC, total nitrogen – TN and total phosphorus – TP), high resolution geochemical (XRF-scanning) and palaeontological (micro- and macro faunal) analysis. The chronological framework is based on five 14C datings forming the basis for an age depth model, calculated using the OxCal software. The radiocarbon dates from previous studies (6 cores, ∼20 dates) were also taken into account. The data synthesis and interpretation provided robust and coherent indications regarding the palaeoenvironment, shoreline changes and the rate of geomorphological changes of the coastal area of Gialova Lagoon, as well as useful information about the palaeonvironmental and palaeoclimatic conditions that prevailed during the Mycenaean period. The interpretation, reveal a transition from a shallow marine environment (6500-5800 yr B.P.) to a brackish/lagoonal (5800-3300 yr B.P.), followed by a shift towards a freshwater/marsh environment (3300 yr B.P. to present).

Late Bronze Age climate change and the destruction of the Mycenaean Palace of Nestor at Pylos.

This paper offers new high-resolution oxygen and carbon isotope data from Stalagmite S1 from Mavri Trypa Cave, SW Peloponnese. Our data provide the climate background to the destruction of the nearby Mycenaean Palace of Nestor at Pylos at the transition from Late Helladic (LH) IIIB to LH IIIC, ~3150–3130 years before present (before AD 1950, hereafter yrs BP) and the subsequent period. S1 is dated by 24 U-Th dates with an averaged precision of ±26 yrs (2σ), providing one of the most robust paleoclimate records from the eastern Mediterranean for the end of the Late Bronze Age (LBA). The δ18O record shows generally wetter conditions at the time when the Palace of Nestor at Pylos was destroyed, but a brief period of drier conditions around 3200 yrs BP may have disrupted the Mycenaean agricultural system that at the time was likely operating close to its limit. Gradually developing aridity after 3150 yrs BP, i.e. subsequent to the destruction, probably reduced crop yields and helped to erode the basis for the reinstitution of a central authority and the Palace itself.

Technology and Provenance Analysis of Glass Fragments from an Ottoman Bathhouse (Hamam) in Kyparissia, Peloponnese, Greece

ABSTRACTThis study focuses on the analysis of a post-medieval assemblage of glass vessels and tableware, recovered from an Ottoman bathhouse in Kyparissia, SW Peloponnese, Greece. The chemical composition of the samples was estimated using SEM/EDS, whereas minor and trace elements were identified by qualitative XRF analysis. Raman spectroscopy was applied in order to examine the connectivity of the silicate glass matrix in more detail. The acquired data indicate significant chemical variations among the samples, especially in regards to the alkali source and the decolourant used. Moreover, one high-lead glass has also been identified. The provenance analysis, which was based on the statistical treatment of the resulted and published analytical data, indicated that the different glass types originated both from the eastern regions of the Ottoman Empire and from glassmaking centres in central and northern Europe. The determination of technology and provenance of the assemblage provided with valuable new information regarding the production and trading network of glass in mainland Greece during the Ottoman rule.

Early Pliocene gastropod assemblages from the eastern Mediterranean (SW Peloponnese, Greece) and their palaeobiogeographic implications

We here report on the systematics, paleoecology and biostratigraphy of a rare, but diversified gastropod fauna found in the early Pliocene sediments of the Agia Triada section in the Falanthi Basin (Peloponnese, Greece). Sixty-one species belonging to forty-eight genera are identified, allowing biostratigraphic assignment to the Mediterranean Plio-Pleistocene Molluscan Unit 1 (MPPMU1). Planktonic foraminiferal biostratigraphic analyses indicate that the Agia Triada section correlates with Zones MPL2 and MPL3, corresponding to the latest Zanclean. A comparison is further carried out between the studied assemblages and those previously documented from the Atlantic coasts of Europe and the Mediterranean region. New information on the palaeobiogeography of early Pliocene gastropod fauna is given, as seven species from the Mediterranean, thirty-nine species from the eastern Mediterranean and forty-four species from Greece, are documented here for the first time.

TECTONOSEDIMENTARY SIGNIFICANCE OF THE MESSINIA CONGLOMERATES (SW PELOPONNESE, GREECE)

The marine fill of the Gavrovo-Tripolis foreland basin in the Messinia area (SW Peloponnese), includes facies and facies associations, deposited by sediment gravity flows in slope and inner fan settings. The above-mentioned gravity-driven sedimentary processes, resulted in the formation of thinning-upward sequences and fining fan facies associations, composed of impressive sheet-conglomerates at the base (Agia Mavra, Agia Varvara and Mali units), presenting mainly normal internal structure, while clay and sand-clay members predominate at the top. These conglomerates advocate a significant sediment supply and extended accommodation space, during periods of dramatic tectonic uplift, associated with the westward propagation of Pindos thrust front. In the prograding fan system, dominate paleo-currents with main flow direction to southwest. The finer fan facies associations show rapid lateral variations, both in lithology and thickness, indicating rapid changes in the inner, incised, part of the foredeep. Nannofossil analyses suggest that the sedimentation took place during Oligocene (NP22 to NP24 biozones). Three NNW-SSE trending thrust fault zones bound the above-mentioned units and they caused an important structural thickening of the fan facies associations. Biostratigraphic analyses date the end of the thrust activity in GavrovoTripolis zone in Late Oligocene (biozone NP24).

Present‐day crustal stress field in Greece inferred from regional‐scale damped inversion of earthquake focal mechanisms

AbstractIn this study we utilize regional and teleseismic earthquake moment tensor solutions in order to infer the contemporary crustal stress in the Greek region. We focus on crustal earthquakes and select only solutions with good waveform fits and well‐resolved nodal planes. A data set of 1614 focal mechanisms is used as input to a regional‐scale damped stress inversion algorithm over a grid whose node spacing is 0.35°. Several resolution and sensitivity tests are performed in order to ascertain the robustness of our results. Our findings show that for most of the Greek region the largest principal stress σ1 is vertically oriented and that the minimum principal stress axis σ3 are subhorizontal with a predominant N‐S orientation. In the SW Peloponnese the orientation of σ3 axes rotates clockwise and in SE Aegean counterclockwise. These results are in agreement with the generally accepted model that slab rollback combined with gravitational spreading of the Aegean lithosphere are the main causes of the extension. Transitions between different faulting types in NW Greece or in the Aegean occur within narrow zones in the order of tens of kilometers. A visual comparison of the principal horizontal stress axes and the principal strain axes derived from GPS observations shows good agreement, suggesting that the crust in the Greek region behaves largely in an elastic manner.

The 2011 Oichalia (SW Peloponnese, Greece) seismic swarm: Geological and seismological evidence for E-W extension and reactivation of the NNW-SSE striking Siamo Fault

The Upper Messinia basin (Peloponnese, Greece) hosted a seismic swarm during the second half of 2011. The geological evidence (surface breaks striking N160°E), the seismological data (distribution of relocated earthquakes and T-axis orientation) and severe damage distribution are aligned along the eastern margin of the basin, so as they are attributed to reactivation of the bordering NNW-SSE normal fault. In particular, the rupture of the 14 August 2011 M=4.8 event is associated to the surface breaks inside the village Siamo. The length of the reactivated fault is estimated as 7 ±1 km based on the longest dimension (NW-SE) of the swarm epicentres (June to October 2011). The mode of rupture of the Siamo fault is probably related to a) the change in stress field orientation from south to north inside the basin (from E-W extension in the Siamo – Katsaro area to N-S extension in the north of Oichalia area) and/or b) to the occurrence of magmatic fluids due to the proximity of Messinia to the Hellenic subduction.

Morphological study of Cyclotella distinguenda with a description of a new fossil species Cyclotella paradistinguenda sp. nov. from the Agios Floros fen, SW Peloponnese, Greece in relation to other Cyclotella species

In a previous palaeoenvironmental study based on a high-resolution diatom record from a core sampled at the Agios Floros fen, SW Peloponnese, Greece, Cyclotella distinguenda was reported as exhibiting two morphs with distinct central area and stria arrangement, as well as a specific distribution throughout the sequence. In the present paper, we examine this morphological variability through detailed observations using light and scanning electron microscope combined with a simple statistical approach. Our new data suggest that the two morphs present substantial and constant differences in the structure and size of their central areas, the structure and number of their striae, the arrangement of their marginal fultoportulae/density of costae between fultoportulae, the shape of their rimoportulae and their alveolar chambers. On the basis of these morphological and stratigraphic variations one morph is described as a new species, Cyclotella paradistinguenda sp. nov., while the other is assigned to C. distinguenda and is also consistent with the original description of this taxon. The two species share well-defined central areas without fultoportulae, almost equal length striae and one rimoportula situated on a costa within the ring of marginal fultoportulae. Cyclotella paradistinguenda sp. nov. can be distinguished by a combination of the following characteristics: (1) large central area (≤1/3 of valve diameter), smooth or decorated with puncta and depressions, flat or concentrically undulated, (2) distinct, narrow striae (12–15/10 µm) consisting of one or two short rows of areolae of the same size expanding into three rows at the mantle, (3) marginal fultoportulae on each first to third costae (4) poorly developed alveolar chambers and rimoportula. Based on the stratigraphic distribution and the associated flora in the Agios Floros sequence, it can be inferred that C. paradistinguenda sp. nov. is tolerant of shallower water conditions with lower nutrient availability and/or higher pH than C. distinguenda.

High-resolution environmental reconstruction in SW Peloponnese, Greece, covering the last c. 6000 years: Evidence from Agios Floros fen, Messenian plain

A paleolimnological record from the central Messenian plain (southwestern Peloponnese, southern Greece) indicates rapid changes in the water level and chemistry of a transient lake on the flanks of the Taygetos Mountains during the last c. 6000 years. The analyses are based on diatoms as well as carbon and nitrogen isotopes from bulk sediments in a 7.5-m-long sediment core retrieved from the drained fen of Agios Floros, at the northern banks of the ancient River Pamisos. The sequence consists of fen peat in the uppermost section underlain by lacustrine sediments, which are punctuated by two layers of clay with diatomaceous silt bands. High accumulation rate is recorded in the oldest part of the section (up to 23 mm/yr), particularly during two decadal-long periods centered at c. 5700 and c. 5300 cal. BP. The diatom record reveals pronounced peaks in the planktonic taxon Cyclotella distinguenda, which correspond to the laminated sequences, reflecting the rapid development of a deep lake with an open water environment during these two time periods. Another two events with intermediate water levels are inferred at c. 5200 and c. 4600 cal. BP. These short-lived phases were probably, to a large extent, caused by local tectonic processes and the consequent hydrological anomalies of the nearby karst springs, although abrupt climatic changes with enhanced precipitation might have also played a role. At c. 4500 cal. BP, our data suggest the development of terrestrial conditions in this area, which can be attributed to the decreasing activity/dry up of springs, probably associated with more arid climate. After c. 2500 cal. BP, the diatom record infers a return to wetter conditions, probably as a response to more humid climate with marked seasonality and human activities, developing the present-day environment with cultivated and seasonally semi-flooded fields.

Application of the Environmental Seismic Intensity scale (ESI 2007) and the European Macroseismic Scale (EMS-98) to the Kalamata (SW Peloponnese, Greece) earthquake (Ms=6.2, September 13, 1986) and correlation with neotectonic structures and active faults

On September 13, 1986, a shallow earthquake (Ms=6.2) struck the city of Kalamata and the surrounding areas (SW Peloponnese, Greece) resulting in 20 fatalities, over 300 injuries, extensive structural damage and many earthquake environmental effects (EEE). The main shock was followed by several aftershocks, the strongest of which occurred two days later (Ms=5.4). The EEE induced by the 1986 Kalamata earthquake sequence include ground subsidence, seismic faults, seismic fractures, rockfalls and hydrological anomalies. The maximum ESI 2007 intensity for the main shock has been evaluated as IX<sub>ESI 2007</sub>, strongly related to the active fault zones and the reactivated faults observed in the area as well as to the intense morphology of the activated Dimiova-Perivolakia graben, which is a 2nd order neotectonic structure located in the SE margin of the Kalamata-Kyparissia mega-graben and bounded by active fault zones. The major structural damage of the main shock was selective and limited to villages founded on the activated Dimiova-Perivolakia graben (IX<sub>EMS-98</sub>) and to the Kalamata city (IX<sub>EMS-98</sub>) and its eastern suburbs (IX<sub>EMS-98</sub>) located at the crossing of the prolongation of two major active fault zones of the affected area. On the contrary, damage of this size was not observed in the surrounding neotectonic structures, which were not activated during this earthquake sequence. It is concluded that both intensity scales fit in with the neotectonic regime of the area. The ESI 2007 scale complemented the EMS-98 seismic intensities and provided a completed picture of the strength and the effects of the September 13, 1986, Kalamata earthquake on the natural and the manmade environment. Moreover, it contributed to a better picture of the earthquake scenario and represents a useful and reliable tool for seismic hazard assessment.

Did the 7/9/1999 M5.9 Athens Earthquake Come with a Warning?

Prior to the 7/9/1999 MS = 5.9 Athens earthquake, regional seismicity has exhibited a power-law increase, of the form �� = K +A(tc −t) n ,w hereis estimated using an expression log � = cM + d and tc is the time of the culminating event. Such changes appeared after the 17/8/1999 M7.4 Izmit event. We quantified the performance of the power law vs. the null hypothesis of constant seismic release rates, by defining the curvature C as the ratio of the power law fit RMS/linear fit RMS, so that the smaller C is, the better the power law behaviour. By mapping C, we have established a critical radius of 110 km and observed that the region of correlated accelerating seismic release extended from the N. Aegean, through Euboea and Attica to the SW Peloponnese. A few days prior to the Athens event, min(C) was centred at the epicentral area and numerical simulation yielded tc = 1999.676 and predicted MS = 5.77. Seismicity rates returned to normal (quasi-constant) after the Athens event. We interpret this effect as critical point behaviour, following remote excitation of a broad area by stress redistribution due to the Izmit event which, at Athens, has triggered 'premature' failure of a fault nearing its load bearing capacity. If this is correct, we have documented a case of remote earthquake triggering by another earthquake, as well as insight into the mechanisms produ- cing it. As a corollary, we note that a large event may beget another large event in its broader region of interaction, which may be preceded by characteristic precursory seismicity changes.

Present‐day dynamics of the Aegean region: A model analysis of the horizontal pattern of stress and deformation

In order to gain quantitative insight into the forces that control the present‐day stress field and pattern of horizontal motions in the Aegean region, we adopt a forward model approach. Mechanisms that have been proposed to explain the present‐day tectonics are represented, to first approximation, in terms of the expected force distributions. On the basis of a thin elastic shell representation of the Aegean lithosphere we then calculate the stress field and displacements associated with these force sets and compare the results with observations of the state of stress based on geological studies of fault kinematics, strain as expressed by earthquake focal mechanisms, and horizontal motions measured by means of satellite geodesy. The two most commonly cited mechanisms suggested to control the Aegean tectonics, (1) the push exerted by the westward moving Anatolian block and (2) forces associated with the Hellenic subduction zone, are first analyzed separately. It is found that the westward Anatolian push alone does not explain the observed prevalence of tensional stress. This is also expressed in a mismatch between the displacements computed to result from the westward push and the observed horizontal velocities. Regarding the forces on the Aegean overriding margin, we find that a model with outward pulling forces of uniform magnitude, acting normal to the arc from the SW Peloponnese to Rhodes, yields a stress field that matches the observed pattern of tension to a large extent. This distribution of forces is consistent with the notion of gravitational spreading of the Aegean lithosphere. The pattern of seismic strain of the overriding margin may evidence the occurrence of a small additional resistive force. Although the prevalence of tension thus appears due mainly to the subduction‐related forces, other aspects of the stress field and also the pattern of horizontal motions indicate that these forces act in combination with westward push. Our model results allow us to address the relation between the forces experienced by the upper plate and the kinematics of subduction, not just in terms of a vertical cross section but also by taking into account the along‐arc dimension.