Gulf Of Corinth Research Articles

Earthquake Diffusion Variations in the Western Gulf of Corinth (Greece)

Earthquake Diffusion Variations in the Western Gulf of Corinth (Greece)

Tropospheric Correction of Sentinel-1 Synthetic Aperture Radar Interferograms Using a High-Resolution Weather Model Validated by GNSS Measurements

Synthetic Aperture Radar Interferometry (InSAR) is a space geodetic technique used for mapping deformations of the Earth’s surface. It has been developed and used increasingly during the last thirty years to measure displacements produced by earthquakes, volcanic activity and other crustal deformations. A limiting factor to this technique is the effect of the troposphere, as spatial and temporal variations in temperature, pressure, and relative humidity introduce significant phase delays in the microwave imagery, thus “masking” surface displacements due to tectonic or other geophysical processes. The use of Numerical Weather Prediction (NWP) models as a tropospheric correction method in InSAR can tackle several of the problems faced with other correction techniques (such as timing, spatial coverage and data availability issues). High-resolution tropospheric modelling is particularly useful in the case of single interferograms, where the removal of the atmospheric phase screen (and especially the highly variable turbulent component) can reveal large-amplitude deformation signals (as in the case of an earthquake). In the western Gulf of Corinth, prominent topography makes the removal of both the stratified and turbulent atmospheric phase screens a challenging task. Here, we investigate the extent to which a high-resolution WRF 1-km re-analysis can produce detailed tropospheric delay maps of the required accuracy by coupling its output (in terms of Zenith Total Delay or ZTD) with the vertical delay component in GNSS measurements. The model is operated with varying physical parameterization in order to identify the best configuration, and validated with GNSS zenithal tropospheric delays, providing a benchmark of real atmospheric conditions. We correct sixteen Sentinel-1A interferograms with differential delay maps at the line-of-sight (LOS) produced by WRF re-analysis. In most cases, corrections lead to a decrease in the phase gradient, with average root-mean-square (RMS) and standard deviation (SD) reductions in the wrapped phase of 6.0% and 19.3%, respectively. Results suggest a high potential of the model to reproduce both the long-wavelength stratified atmospheric signal and the short-wave turbulent atmospheric component which are evident in the interferograms.

Use of GNSS Tropospheric Delay Measurements for the Parameterization and Validation of WRF High-Resolution Re-Analysis over the Western Gulf of Corinth, Greece: The PaTrop Experiment

In the last thirty years, Synthetic Aperture Radar interferometry (InSAR) and the Global Navigation Satellite System (GNSS) have become fundamental space geodetic techniques for mapping surface deformations due to tectonic movements. One major limiting factor to those techniques is the effect of the troposphere, as surface velocities are of the order of a few mm yr−1, and high accuracy (to mm level) is required. The troposphere introduces a path delay in the microwave signal, which, in the case of GNSS Precise Point Positioning (PPP), can nowadays be partly removed with the use of specialized mapping functions. Moreover, tropospheric stratification and short wavelength spatial turbulences produce an additive noise to the low amplitude ground deformations calculated by the (multitemporal) InSAR methodology. InSAR atmospheric phase delay corrections are much more challenging, as opposed to GNSS PPP, due to the single pass geometry and the gridded nature of the acquired data. Thus, the precise knowledge of the tropospheric parameters along the propagation medium is extremely useful for the estimation and correction of the atmospheric phase delay. In this context, the PaTrop experiment aims to maximize the potential of using a high-resolution Limited-Area Model for the calculation and removal of the tropospheric noise from InSAR data, by following a synergistic approach and integrating all the latest advances in the fields of remote sensing meteorology (GNSS and InSAR) and Numerical Weather Forecasting (WRF). In the first phase of the experiment, presented in the current paper, we investigate the extent to which a high-resolution 1 km WRF weather re-analysis can produce detailed tropospheric delay maps of the required accuracy, by coupling its output (in terms of Zenith Total Delay or ZTD) with the vertical delay component in GNSS measurements. The model is initially operated with varying parameterization, with GNSS measurements providing a benchmark of real atmospheric conditions. Subsequently, the final WRF daily re-analysis run covers an extended period of one year, based on the optimum model parameterization scheme demonstrated by the parametric analysis. The two datasets (predicted and observed) are compared and statistically evaluated, in order to investigate the extent to which meteorological parameters that affect ZTD can be simulated accurately by the model under different weather conditions. Results demonstrate a strong correlation between predicted and observed ZTDs at the 19 GNSS stations throughout the year (R ranges from 0.91 to 0.93), with an average mean bias (MB) of –19.2 mm, indicating that the model tends to slightly underestimate the tropospheric ZTD as compared to the GNSS derived values. With respect to the seasonal component, model performance is better during the autumn period (October–December), followed by spring (April–June). Setting the acceptable bias range at ±23 mm (equal to the amplitude of one Sentinel-1 C-band phase cycle when projected to the zenithal distance), it is demonstrated that the model produces satisfactory results, with a percentage of ZTD values within the bias margin ranging from 57% in summer to 63% in autumn.

Is There a Speed Limit for the Thermal Steady‐State Assumption in Continental Rifts?

AbstractThe lithosphere is often assumed to reside in a thermal steady‐state when quantitatively describing the temperature distribution in continental interiors and sedimentary basins, but also at active plate boundaries. Here, we investigate the applicability limit of this assumption at slowly deforming continental rifts. To this aim, we assess the tectonic thermal imprint in numerical experiments that cover a range of realistic rift configurations. For each model scenario, the deviation from thermal equilibrium is evaluated. This is done by comparing the transient temperature field of every model to a corresponding steady‐state model with an identical structural configuration. We find that the validity of the thermal steady‐state assumption strongly depends on rift type, divergence velocity, sampling location, and depth within the rift. Maximum differences between transient and steady‐state models occur in narrow rifts, at the rift sides, and if the extension rate exceeds 0.5–2 mm/a. Wide rifts, however, reside close to thermal steady‐state even for high extension velocities. The transient imprint of rifting appears to be overall negligible for shallow isotherms with a temperature less than 100°C. Contrarily, a steady‐state treatment of deep crustal isotherms leads to an underestimation of crustal temperatures, especially for narrow rift settings. Thus, not only relatively fast rifts like the Gulf of Corinth, Red Sea, and Main Ethiopian Rift, but even slow rifts like the Kenya Rift, Rhine Graben, and Rio Grande Rift must be expected to feature a pronounced transient component in the temperature field and to therefore violate the thermal steady‐state assumption for deeper crustal isotherms.

Connecting subduction, extension and shear localization across the Aegean Sea and Anatolia

SUMMARY The Eastern Mediterranean is the most seismically active region in Europe due to the complex interactions of the Arabian, African, and Eurasian tectonic plates. Deformation is achieved by faulting in the brittle crust, distributed flow in the viscoelastic lower-crust and mantle, and Hellenic subduction, but the long-term partitioning of these mechanisms is still unknown. We exploit an extensive suite of geodetic observations to build a kinematic model connecting strike-slip deformation, extension, subduction, and shear localization across Anatolia and the Aegean Sea by mapping the distribution of slip and strain accumulation on major active geological structures. We find that tectonic escape is facilitated by a plate-boundary-like, trans-lithospheric shear zone extending from the Gulf of Evia to the Turkish-Iranian Plateau that underlies the surface trace of the North Anatolian Fault. Additional deformation in Anatolia is taken up by a series of smaller-scale conjugate shear zones that reach the upper mantle, the largest of which is located beneath the East Anatolian Fault. Rapid north–south extension in the western part of the system, driven primarily by Hellenic Trench retreat, is accommodated by rotation and broadening of the North Anatolian mantle shear zone from the Sea of Marmara across the north Aegean Sea, and by a system of distributed transform faults and rifts including the rapidly extending Gulf of Corinth in central Greece and the active grabens of western Turkey. Africa–Eurasia convergence along the Hellenic Arc occurs at a median rate of 49.8 mm yr–1 in a largely trench-normal direction except near eastern Crete where variably oriented slip on the megathrust coincides with mixed-mode and strike-slip deformation in the overlying accretionary wedge near the Ptolemy–Pliny–Strabo trenches. Our kinematic model illustrates the competing roles the North Anatolian mantle shear zone, Hellenic Trench, overlying mantle wedge, and active crustal faults play in accommodating tectonic indentation, slab rollback and associated Aegean extension. Viscoelastic flow in the lower crust and upper mantle dominate the surface velocity field across much of Anatolia and a clear transition to megathrust-related slab pull occurs in western Turkey, the Aegean Sea and Greece. Crustal scale faults and the Hellenic wedge contribute only a minor amount to the large-scale, regional pattern of Eastern Mediterranean interseismic surface deformation.

The Cult of Poseidon Helikonios

The cult of Poseidon Helikonios is associated with his primeval aspect of the powerful god of earthquakes and waters. His most antique cult in this capacity, dating from the Mycenaean times, originates from Helike of Achaea on the southwestern shore of the Gulf of Corinth, the place known to Homer as a centre of this worship. The sanctuary of Poseidon Helikonios located in Helike was the holiest for all Ionians; there were also located the ancient ancestral altars for the Ionic race. When the Ionians were expelled from Helike by the Achaeans at the end of the Mycenaean times, they settled in Asia Minor and carried with them the cult of Helikonios . In the paper, the spread of this particular cult from Helike to the Asia Minor coast and farther to the Black Sea region is discussed on the basis of literary, archaeological and numismatic evidence available from the places where the cult held prominent position.

A constrained-memory stress release model (CM-SRM) for the earthquake occurrence in the Corinth Gulf (Greece)

The complexity of seismogenesis requires the development of stochastic models, the application of which aims to improve our understanding on the seismic process and the associated underlying mechanisms. Seismogenesis in the Corinth Gulf (Greece) is modeled through a Constrained-Memory Stress Release Model (CM-SRM), which combines the gradual increase of the strain energy due to continuous slow tectonic strain loading and its sudden release during an earthquake occurrence. The data are treated as a point process, which is uniquely defined by the associated conditional intensity function. In the original form of the Simple Stress Release Model (SSRM), the conditional intensity function depends on the entire history of the process. In an attempt to identify the most appropriate parameterization that better fits the data and describes the earthquake generation process, we introduce a constrained “ $$m$$ -memory” point process, implying that only the $$m$$ most recent arrival times are taken into account in the conditional intensity function, for some suitable $$m \in N$$ . Modeling of this process is performed for moderate earthquakes (M ≥ 5.2) occurring in the Corinth Gulf since 1911, by considering in each investigation different number of steps backward in time. The derived model versions are compared with the SSRM in its original form and evaluated in terms of information criteria and residual analysis.

Using Kinematic GNSS Data to Assess the Accuracy and Precision of the TanDEM-X DEM Resampled at 1-m Resolution Over the Western Corinth Gulf, Greece

We assess the accuracy and the precision of the TanDEM-X digital elevation model (DEM) of the western Gulf of Corinth, Greece. We use a dense set of accurate ground coordinates obtained by kinematic Global Navigation Satellite Systems (GNSS) observations. Between 2001 and 2019, 148 surveys were made, at a 1 s sampling rate, along highways, roads, and tracks, with a total traveled distance of ∼25 000 km. The data are processed with the online Canadian Spatial Reference System precise point positioning software. From the output files, we select 885 252 coordinates from epochs with theoretical uncertainty below 0.1 m in horizontal and 0.2 m in vertical. Using specific calibration surveys, we estimate the mean vertical accuracy of the GNSS coordinates at 0.2 m. Resampling the DEM by a factor of 10 allows one to compare it with the GNSS in pixels of metric size, smaller than the width of the roads, even the small trails. The best fit is obtained by shifting the DEM by 0.47 ± 0.03 m upward, 0.10 ± 0.1 m westward, and 0.36 ± 0.1 m southward. Those values are 20 times below the nominal resolution of the DEM. Once the shift is corrected, the root mean square deviation between TanDEM-X DEM and GNSS elevations is 1.125 m. In forest and urban areas, the shift between the DEM and the GNSS increases by ∼0.5 m. The metric accuracy of the TanDEM-X DEM paves the way for new applications for long-term deformation monitoring of this area.

Application of Non-Destructive Techniques on a Varve Sediment Record from Vouliagmeni Coastal Lake, Eastern Gulf of Corinth, Greece

During the last few decades, X-ray attenuation systems have been established as standard techniques in geosciences and as excellent scientific tools for the analysis of sedimentary facies and structures. In the present study, we use two non-destructive and high-resolution systems (computed tomography, X-ray fluorescence) to address all sedimentological facies and structural characteristics on a 6 m long, partly laminated sediment record, from Vouliagmeni lake, located at the eastern part of the Corinth Gulf, Greece. Vouliagmeni lake is the deepest coastal lake in Greece, and its location is of great importance since it is located in one of the most tectonically active regions in the world. The chronological framework of the retrieved sediment sequence spans the last 12,000 years, with alternations of laminated and non-laminated sections. The annual accumulation of the laminated sequences was determined through the radionuclide concentration of 14 samples. Scanning tomography was performed with a medical CT scanner and a μCT scanner, aiming to compare the potentials and variations of both methods. Lamination boundaries, event layers (turbidites) and sediment deformations were distinguished through processing the extracted 3D rendered volumes, after applying ranges depending on Hounsfield (HU) values. Microscopic analysis revealed three main layer types in the varve sequences that were examined, attributing to summer/spring, autumn and winter deposits. Statistical analysis of the elemental composition, magnetic susceptibility (MS) measurements and HU values revealed three clusters/facies, reflecting climatic and in-lake hydrological changes. Cluster A emulates sedimentation during arid conditions, while Cluster B reflects humid conditions with increased precipitation and erosion. Cluster C represents sequences with homogenous Ca-rich sediment. Our proposed workflow highlights the possible correlation between the non-destructive variables that were measured, but also the variations and applications of each method and software used during this study.

Tectonic crustal deformation of Corinth Gulf, Greece, based on primary geodetic data

Tectonic crustal deformation of Corinth Gulf, Greece, based on primary geodetic data

Implementation challenges of maritime spatial planning (MSP) in Greece under a place-based approach

In the era of blue growth, maritime spatial planning (MSP)—especially MSP using a place-based approach—is absolutely essential if the sustainable management of oceans and seas is to be achieved. This paper therefore presents relevant lessons learnt from a study of a pilot marine area of Greece (the Inner Ionian Sea—Corinthian Gulf region). The study showed that, in order to develop and perform efficient place-based MSP in Greece, it is necessary to strengthen cross-border cooperation among countries that share the eastern Mediterranean Sea, to effectively engage the maritime regime and stakeholders in governance schemes, to collect and manage marine geospatial data, and to have a good grasp of the tools and methodologies that can be used in MSP. Moreover, the present paper identifies suitable criteria for defining appropriate MSP management units, considering ecosystem boundaries, management boundaries, geopolitical boundaries, socioeconomic and cultural characteristics, and land–sea interactions. The process of identifying the optimal MSP management units is underway in Greece; this step is crucial to performing place-based MSP and, ultimately, MSP utilizing the ecosystem-based approach.

Chronology of Quaternary shoreline progradational sequences related to eustatic sea-level changes: Sedimentation and subsidence in Saronikos Gulf, Greece

The stacking pattern of shoreline progradational sequences in subsiding basins have been used as a chronologic tool in the Mediterranean region. Most previous studies have used a few key seismic lines seaward of deltas, where the record is complicated by deltaic distributary switching. Southeastern Saronikos Gulf, in the western Aegean Sea at the northwestern end of the South Aegean Arc, lacks large river input of sediment. The ENE-WSW and NW-SE trending neotectonic Aegina and Methana basins lie between the tectonically active Gulf of Corinth and the relatively stable Cyclades plateau. New high-resolution seismic profiles from southeastern Saronikos Gulf have been interpreted according to the principles of seismic and sequence stratigraphy. Alpine basement and marine Pliocene sediments have been recognized in the surrounding basin margins and more than 300 m and 150 m of unconsolidated sediments have been mapped in Aegina and Methana basin respectively. Progradational clinoforms that toplap against transgressive surfaces, have been traced along strike, leading to the establishment of a robust chronostratigraphic framework further controlled by sedimentation rates as extracted from cores. Southeastern Saronikos Gulf poses an outstanding example of development of progradational wedges formed within a microtidal, wave dominated regime of low sedimentation rates, between 2.8 cm/ka and 3.2 cm/ka, within the framework of low subsiding basins with rates between 0.03 and 0.31 m/ka. In this environment, more than 180 well preserved shoreline progradational units, with attributes similar to the ones reported from the Aegean and Eastern Mediterranean seas, have been mapped and correlated to sea level lowstands back to 866 ka. Deeper Mid-Pleistocene progradational units are also recognized, tentatively back to 1.4 Ma. Subsidence rate shows a dramatic decrease in the last 1 Ma and significant numbers of faults became inactive during the last 130 ka. In Early-Middle Quaternary, Methana basin was an isolated lake and extended terrestrial areas were shaped in the Poros-Agios Georgios plateau during sea level lowstands. Aegina basin was continuously connected to the Aegean through the Agios Georgios fault valley. This study demonstrates the robustness of chronology based on stacked shoreline progradational sequences and its applicability to determining rates of tectonic subsidence.

Palaeoenvironmental evolution of a coastal lagoon as a response to climate oscillations during the Early Pleistocene: a case study from Sousaki Basin (Eastern Gulf of Corinth, Greece)

Climatic oscillations during the Pleistocene were controlled by glacial/interglacial cycles. Such oscillations are commonly imprinted into sediments and fossils from transitional marine environments, as is also the case in Sousaki Basin (Eastern Gulf of Corinth, Greece). Nevertheless, the records become scarcer as we go back in time. During the Lower Pleistocene, Sousaki Basin (Eastern Gulf of Corinth, Greece), was dominated by transitional marine environments. Micropalaeontological analysis has been carried out in sedimentary sequences to identify the evolution of the palaeoenvironments in an area where intense tectonic activity occurred, being at the western end of the Hellenic volcanic arc and at the eastern end of the Corinth rift. The recovered ostracod assemblage revealed a primarily brackish environment. Deposition took place in a coastal lagoon which was subjected to constant salinity changes. The palaeoenvironment in the basin evolved from a delta fan environment to an outer lagoon with possible connection to a sublittoral marine environment at the top. This evolution coincides and therefore is attributed to minor climate oscillations that occurred during the Early Pleistocene.

Quaternary continental shelf basins of Saronikos Gulf, Aegean Sea

The Saronikos Gulf hosts the northwestern end of the South Aegean Active Volcanic Arc. It is affected by extensional back-arc tectonism in a prominent N-S direction, while older E-W rifting is also manifested. Recently acquired swath bathymetry and high-resolution seismic profiles led to the precise morphological mapping of five Quaternary continental shelf basins, along with their neotectonic delineations and their cross-correlation to the onshore active fault zones. Aegina and Methana basins, in the southeast Saronikos Gulf, display subsidence along ENE-WSW and NW-SE axes, and continuous marine sedimentation throughout the Upper Quaternary. Salamina basin in the northeast Saronikos Gulf is a shallow, relatively stable sedimentary basin, intermittently connected to the SE and NW Saronikos Gulf through the Aegina-Fleves and the Aegina-Salamina plateau respectively. In the western and most active region of Saronikos Gulf, the onshore E-W–trending faults of Kechrees and Agios Vassileios extend eastwards until the Salamina-Aegina plateau. The Megara basin is WNW-ESE oriented, possibly affected by the N-S Korfos fault valley, which connects the Megara and Epidavros basins. E-W–trending faults tilt the Quaternary sedimentary blocks, in compatibility to the N-S extensional tectonic regime of the adjacent Gulf of Corinth. Prograding clinoforms in the Megara and Epidavros basins reveal an Upper Quaternary-age intermittent connection to the open sea. Mass transport deposits and volcanic flows in-between the Upper Quaternary sediments of the Epidavros basin manifest the 500–400 ka tectonic phase that affected both the NE Peloponnese coast and the active N-S and NW-SE to WNW-ESE striking faults of the Epidavros basin margin.

Imbricated Aseismic Slip and Fluid Diffusion Drive a Seismic Swarm in the Corinth Gulf, Greece

AbstractThe primary processes driving seismic swarms are still under debate. Here, we study the temporal evolution of a seismic swarm that occurred over a 10‐day period in October 2015 in the extensional rift of the Corinth Gulf (Greece) using high‐resolution earthquakes relocations. The seismicity radially migrates on a normal fault at a fluid diffusion velocity (~125 m/day). However, this migration occurs intermittently, with periods of fast expansion (2 to 10 km/day) during short seismic bursts alternating with quiescent periods. Moreover, the growing phases of the swarm illuminate a high number of repeaters. The swarm migration is likely the results of a combination of multiple driving processes. Fluid upflow in the fault may induce aseismic slip episodes, separated by phases of fluid pressure build‐up. The stress perturbation due to aseismic slip may activate small asperities that produce bursts of seismicity during the most intense phases of the swarm.

Distributed normal faulting in the tip zone of the South Alkyonides Fault System, Gulf of Corinth, constrained using 36Cl exposure dating of late-Quaternary wave-cut platforms

The geometry, rates and kinematics of active faulting in the region close to the tip of a major crustal-scale normal fault in the Gulf of Corinth, Greece, are investigated using detailed fault mapping and new absolute dating. Fault offsets have been dated using a combination of 234U/230Th coral dates and in situ36Cl cosmogenic exposure ages for sediments and wave-cut platforms deformed by the faults. Our results show that deformation in the tip zone is distributed across as many as eight faults arranged within ~700 m across strike, each of which deforms deposits and landforms associated with the 125 ka marine terrace of Marine Isotope Stage 5e. Summed throw-rates across strike achieve values as high as 0.3–1.6 mm/yr, values that are comparable to those at the centre of the crustal-scale fault (2–3 mm/yr from Holocene palaeoseismology and 3–4 mm/yr from GPS geodesy). The relatively high deformation rate and distributed deformation in the tip zone are discussed in terms of stress enhancement from rupture of neighbouring crustal-scale faults and in terms of how this should be considered during fault-based seismic hazard assessment.

Straight from the source's mouth: Controls on field‐constrained sediment export across the entire active Corinth Rift, central Greece

AbstractThe volume and grain‐size of sediment supplied from catchments fundamentally control basin stratigraphy. Despite their importance, few studies have constrained sediment budgets and grain‐size exported into an active rift at the basin scale. Here, we used the Corinth Rift as a natural laboratory to quantify the controls on sediment export within an active rift. In the field, we measured the hydraulic geometries, surface grain‐sizes of channel bars and full‐weighted grain‐size distributions of river sediment at the mouths of 47 catchments draining the rift (constituting 83% of the areal extent). Results show that the sediment grain‐size increases westward along the southern coast of the Gulf of Corinth, with the coarse‐fraction grain‐sizes (84th percentile of weighted grain‐size distribution) ranging from approximately 19 to 91 mm. We find that the median and coarse‐fraction of the sieved grain‐size distribution are primarily controlled by bedrock lithology, with late Quaternary uplift rates exerting a secondary control. Our results indicate that grain‐size export is primarily controlled by the input grain‐size within the catchment and subsequent abrasion during fluvial transport, both quantities that are sensitive to catchment lithology. We also demonstrate that the median and coarse‐fraction of the grain‐size distribution are predominantly transported in bedload; however, typical sand‐grade particles are transported as suspended load at bankfull conditions, suggesting disparate source‐to‐sink transit timescales for sand and gravel. Finally, we derive both a full Holocene sediment budget and a grain‐size‐specific bedload discharged into the Gulf of Corinth using the grain‐size measurements and previously published estimates of sediment fluxes and volumes. Results show that the bedload sediment budget is primarily comprised (~79%) of pebble to cobble grade (0.475–16 cm). Our results suggest that the grain‐size of sediment export at the rift scale is particularly sensitive to catchment lithology and fluvial mophodynamics, which complicates our ability to make direct inferences of tectonic and palaeoenvironmental forcing from local stratigraphic characteristics.

Spatial distribution modelling of striped dolphin (Stenella coeruleoalba) at different geographical scales within the EU Adriatic and Ionian Sea Region, central‐eastern Mediterranean Sea

Abstract The striped dolphin (Stenella coeruleoalba) is one of the most abundant cetaceans of the Mediterranean Sea. Nevertheless, it is ranked as ‘Vulnerable’ by IUCN Red List experts. To implement conservation strategies within the Mediterranean Sea, it is crucial to understand how striped dolphins are distributed at different geographical scales. The present study investigates its distribution within the EU Adriatic and Ionian Sea Region. To model striped dolphin distribution, topographic (distance from shore, depth and slope) and oceanographic variables (sea surface temperature and phytoplankton concentration) were employed, and species distribution models (SDMs) were developed using Maxent software. Generalized additive models (GAMs) were used to improve the information supplied by the SDMs, allowing the description of response curves to striped dolphin occurrences. Statistical analysis shows that striped dolphins are not evenly distributed within the investigated area. The higher encounter rates observed in the Gulf of Taranto and the Gulf of Corinth confirm that both sub‐regions are crucial for its conservation. Furthermore, SDMs also indicate suitable areas in the offshore waters of the Adriatic Sea, along the continental slope of the north‐eastern Ionian Sea and over its continental shelf. Within the EU Adriatic and Ionian Sea Region, striped dolphins prefer areas at a greater distance from shore, with steeper slopes, deeper waters, and higher sea surface temperature. The topographic variables are the most explicative factors for both modelling approaches. The analysis of striped dolphin SDMs allows the identification of important areas for conservation and highlights zones where appropriate mitigation strategies could reduce the impact of human activities on this Vulnerable species. Further analysis of SDMs for different periods of the year, as well as a genetic study, could highlight seasonal movements across and within sub‐regions.

Site Amplification Assessment in the East Corinth Gulf Using 3D Finite-Difference Modeling and Local Geophysical Data

Elastic 3D wave-field simulations were performed in the seismically active region of Eastern Gulf of Corinth, in the area of Loutraki city. A new methodology was tested with the aim of performing multiple simulations for a large variety of realistic sources located around the study area, by employing 3D finite-difference modeling using matrix operations for the calculation of the spatial velocity and stress derivatives. The new methodology was proven to be quite efficient in simulating the near surface 3D site effect of the study area, by greatly minimizing the simulation time, thus allowing the use of 3D finite-difference modeling for a large number of simulations. The complex geological features of the study area were obtained by performing multiple passive MASW surveys within the busy urban area of Loutraki. By processing the acquired geophysical data, a highly inhomogeneous near surface velocity structure in the study area was obtained and was implemented in the 3D wave-field simulations. The near surface amplification that is caused by the 3D subsurface structure was proven to be highly significant for the area of Loutraki, with high spectral amplification compared to the amplification that is caused by an equivalent 1D model in the area. The dominant frequencies of the spectral amplification for the 3D model were also confirmed by Processing HVSR measurements that were also taken in the area. Finally, we also investigated how the propagation direction affects the near surface amplification.

Recent sedimentation rates using 210Pb and 137Cs vertical profiles of core sediments at the Gulf of Corinth, Litochoro Coast and Marmara Sea

In this work, core sediment samples up to 50 cm have been collected from three different marine environments; Gulf of Corinth, Gulf of Thermaikos, specifically from Litochoro Coast and Lake Uluabat from the wider region of Black Sea. Natural (210Pb) and anthropogenic (137Cs) radionuclides in the samples were measured using an HPGe detector, calibrated for sediments geometry. The vertical distribution of 137Cs and 210Pb was used to determine the sedimentation rate. The results were 0.56 cm/year for the Gulf of Corinth and 0.54 cm/year for the coast of Litochoro. In the case of the lake Uluabat the sedimentation rate was 0.41 cm/year.