Emmanuel Vassilakis

Remote Sensing of Environmental Change in the Antirio Deltaic Fan Region, Western Greece

In the westernmost region of the rapidly widening Corinth rift, Greece, extensive development of roads, bridges and other human infrastructure has caused continuous environmental change over the past twenty years. River networks, the land surface and the coastal environment, have been altered, especially in the areas corresponding to deltaic fans. In this paper we use earth observation systems that have captured these environmental changes, particularly medium (Landsat TM and ETM+) and high (Quickbird) resolution satellite images, to identify environmental changes between the periods 1992, 2000, 2002, and 2005. Six pseudo-color multi-temporal images in different spectral areas were created in order to detect changes to the terrestrial and coastal environment caused mainly by direct or indirect human impact. This methodology provided new data for quantifying significant alterations in the environment on different scales. In many cases this revealed their sequence during the time of observation.

Vertical-axis rotations accommodated along the Mid-Cycladic lineament on Paros Island in the extensional heart of the Aegean orocline (Greece)

The Aegean–west Anatolian orocline formed due to Neogene opposite rotations of its western and eastern limbs during opening of the Aegean back-arc basin. Stretching lineations in exhumed metamorphic complexes in this basin mimic the regional vertical-axis rotation patterns and suggest that the oppositely rotating domains are sharply bounded along a Mid-Cycladic lineament, the tectonic nature of which is enigmatic. Some have proposed this lineament to be an extensional fault accommodating orogen-parallel extension, while others have considered it to be a transform fault. The island of Paros hosts the only exposure of the E- to NE-trending lineations characterizing the NW Cyclades and the N-trending lineations of the SE Cyclades. Here, we show new paleomagnetic results from isotropic, ca. 16 Ma granitoids that intruded both domains and demonstrate that the trend difference resulted from post–16 Ma ∼90° clockwise and 10° counterclockwise rotation of the NW and SE blocks, respectively. We interpret the semiductile to brittle, low-angle, SE-dipping Elitas shear zone that accommodated this rotation difference to reflect the Mid-Cycladic lineament. We conclude a two-stage exhumation history for Paros that is consistent with regional Aegean reconstructions. Between ca. 23 and 16 Ma, the metamorphic rocks of Paros were exhumed from amphibolite-facies to greenschist-facies conditions along a top-to-the-N detachment. The Elitas shear zone then started to exhume the northwestern, clockwise-rotating domain from below the southeastern, counterclockwise rotating domain since 16 Ma. From this, we infer that the Mid-Cycladic lineament is an extensional shear zone, consistent with geometric predictions that Aegean oroclinal bending was accommodated by orogen-normal and orogen-parallel extension.

Crustal stress and seismic activity in the Ionian archipelago as inferred by satellite- and ground-based observations, Kefallinia, Greece

Abstract Different observational techniques are compared in order to investigate possible correlations in seismic activity. The study site is the island of Kefallinà (Greece), where measurements available included (1) DInSAR, DGPS, and DEM data, (2) soil exhalation measured by monitoring Radon (Rn) well content, and (3) acoustic emissions (AE) at high and low frequency (point-like records with high temporal resolution). AE records provide: (1) relative time variation of the applied stress intensity and (2) the state of fatigue of stressed rock volumes, the AE source. Our results indicate that the large spatial scale (poor time resolution) may be considered quite satisfactory, whereas fractal analysis of the AE time series displayed some discrepancies when compared to analogous investigations in the Italian Peninsula. Therefore, some refinement is needed in order to reach more precise interpretations of the relevant information available with this kind of data. However, both sets of observations appear in agreement with each other, although more exhaustive investigations would require a suitable array of point-like AE and Rn (or other) measuring sites, as well as longer data series. The latter are particularly helpful for detailed interpretations of the different occurrences within tectonically complex settings where crustal stress crises are marked by various types of geological phenomena.

Quantification of Deltaic Coastal Zone Change Based on Multi-Temporal High Resolution Earth Observation Techniques

A series of methodologies are described in this paper aiming to quantify the natural hazard due to the coastal changes at a deltaic fan. The coastline of Istiaia (North Evia, Greece) has been chosen for this study as several areas of accretion and erosion have been identified during the past few decades. We combined different types of datasets, extracted from high resolution panchromatic aerial photographs and traced the contemporary shoreline by high accuracy surveying with Real Time Kinematics (RTK) GPS equipment. The interpretation of all shorelines required geo-statistical analysis in a Geographical Information System. A large number of high resolution morphological sections were constructed normally to the coast, revealing erosional and depositional parts of the beach. Retreating and extension rates were calculated for each section reaching the values of 0.98 m/yr and 1.36 m/yr, respectively. The results proved to be very accurate, allowing us to expand the developed methodology by using more complete time-series of remote sensing datasets along with more frequent RTK-GPS surveying.

Assessment of continuous sky view factor based on ultra-high resolution natural colour images acquired by remotely piloted airborne systems for applications in an urban area of Athens

ABSTRACT The thermal comfort conditions in a complex urban area is influenced by the surrounding structures and obstacles which modify the incoming radiation fluxes. A measure of this modification is the sky view factor (SVF), which could be estimated in each point of a selected area if a high resolution digital elevation model (DEM), or other urban morphological data including the manmade infrastructure, are available. The goal of this study is to model the continuous SVF for a complex building environment in the campus of National and Kapodistrian University of Athens, based on a high resolution DEM (0.09 m). For this purpose, we applied the structure-from-motion (SfM) technique, which takes advantage of the interpretation of ultra-high resolution colour images acquired by remotely piloted airborne systems, also known as drones or unmanned aerial vehicles. A quantitative analysis, by applying statistical metrics, yields perfect agreement between modelled and observed SVF values, over the examined area. The proposed methodology could be applied for human-biometeorology research in micro scale complex urban environments.