Experimental evidence of a non-extensive statistical physics behavior of electromagnetic signals emitted from rocks under stress up to fracture. Preliminary results

The application of mechanical stress on a rock sample can induce electromagnetic emissions. Such emissions can be detected experimentally and in principle could be used as precursors of the upcoming failure.     

Three-Dimensional Numerical Investigation of the Interaction Between Twin Tunnels

Geotechnical and Geological Engineering - The construction of twin tunnels is a mandatory guideline and a prevailing practice in either conventional or mechanized tunneling. Nevertheless, most of...     

Aftershock patterns of the 2021 Mw 6.3 Northern Thessaly (Greece) earthquake

Journal of Seismology - On March 3, 2021, a strong shallow earthquake of magnitude Mw 6.3 struck Northern Thessaly, an area that lies in one of the most active fault zones of mainland Greece. The...     

Non-extensive statistical physics approach to fault population distribution. A case study from the southern Hellenic arc (Central Crete)

Fault population statistics play a key role in the understanding of any statistical seismicity approach. In the present work a non-extensive statistical physics approach is formulated and tested for the local fault length distribution. The approach is composed of the following parts: (i) Tsallis entropy, S _q , (ii) maximization of the Tsallis entropy under appropriate constrains, and (iii) derivation of the cumulative distribution function (CDF) of the fault length population. This model is tested using fault length data from the Central Crete graben in front of the Hellenic arc and estimated a thermodynamic q parameter equal to 1.16, which supports the conclusion that the fault system in Central Crete graben is a sub-extensive one.     

Aquifer characterization using shallow geophysics in the Keritis Basin of Western Crete, Greece

Effective management of groundwater resources is a well-known problem in several areas around the world. It is especially important to areas suffering from an intrinsic lack of fresh water, such as islands. Detailed study of available aquifers is of particular interest in the highly touristic Greek island of Crete. The increasing water demand makes water resources management extremely important for sustainable development. This is the case in the prefecture of Chania in Western Crete, where there has been a lack of success of many different groundwater management plans that have been produced over the years and submitted for application to water management authority. The inefficiency of the management plans is verified by the continuous water shortage reported every year which forces the public authorities to transfer water from far away sources and wells. Until today there are only geological data as well as information from the borehole logs; therefore, the current work is focused to study in detail the tectonic and hydrogeological characteristics of the Keritis watershed to make a correlation of the available geoenvironmental information with the geophysical data of the study aquifer. Transient electromagnetic soundings were conducted to obtain detailed information about: the tectonic, hydrogeological, hydrolithological, and geometrical characteristics of the aquifer under investigation. In addition, optimum areas of water well drilling were identified to minimize the uncertainty and the total cost (economical, managerial, etc.) of future groundwater surveys.     

Post‐impact structural crater modification due to sediment loading: An overlooked process

Abstract— Post‐impact crater morphology and structure modifications due to sediment loading are analyzed in detail and exemplified in five well‐preserved impact craters: Mjølnir, Chesapeake Bay, Chicxulub, Montagnais, and Bosumtwi. The analysis demonstrates that the geometry and the structural and stratigraphic relations of post‐impact strata provide information about the amplitude, the spatial distribution, and the mode of post‐impact deformation. Reconstruction of the original morphology and structure for the Mjølnir, Chicxulub, and Bosumtwi craters demonstrates the long‐term subsidence and differential compaction that takes place between the crater and the outside platform region, and laterally within the crater structure. At Mjølnir, the central high developed as a prominent feature during post‐impact burial, the height of the peak ring was enhanced, and the cumulative throw on the rim faults was increased. The original Chicxulub crater exhibited considerably less prominent peak‐ring and inner‐ring/crater‐rim features than the present crater. The original relief of the peak ring was on the order of 420–570 m (currently 535–575 m); the relief on the inner ring/crater rim was 300–450 m (currently ?700 m). The original Bosumtwi crater exhibited a central uplift/high whose structural relief increased during burial (current height 101–110 m, in contrast to the original height of 85–110 m), whereas the surrounding western part of the annular trough was subdued more that the eastern part, exhibiting original depths of 43–68 m (currently 46 m) and 49–55 m (currently 50 m), respectively. Furthermore, a quantitative model for the porosity change caused by the Chesapeake Bay impact was developed utilizing the modeled density distribution. The model shows that, compared with the surrounding platform, the porosity increased immediately after impact up to 8.5% in the collapsed and brecciated crater center (currently +6% due to post‐impact compaction). In contrast, porosity decreased by 2–3% (currently ?3 to ?4.5% due to post‐impact compaction) in the peak‐ring region. The lateral variations in porosity at Chesapeake Bay crater are compatible with similar porosity variations at Mjølnir crater, and are considered to be responsible for the moderate Chesapeake Bay gravity signature (annular low of ?8 mGal instead of ?15 mGal). The analysis shows that the reconstructions and the long‐term alterations due to post‐impact burial are closely related to the impact‐disturbed target‐rock volume and a brecciated region of laterally varying thickness and depth‐varying physical properties. The study further shows that several crater morphological and structural parameters are prone to post‐impact burial modification and are either exaggerated or subdued during post‐impact burial. Preliminary correction factors are established based on the integrated reconstruction and post‐impact deformation analysis. The crater morphological and structural parameters, corrected from post‐impact loading and modification effects, can be used to better constrain cratering scaling law estimates and impact‐related consequences.     

Landslide hazard zonation in high risk areas of Rethymno Prefecture,Crete Island,Greece

The central part of Rethymnon Prefecture, Crete Island, suffers from severe landslide phenomena because of its geological and geomorphological settings alternated by the human activities. The main landslide preparatory and triggering causal factors are considered to be the ground conditions (lithology), geomorphological processes (fluvial erosion, etc.), and the man-made actions (excavations, loading etc.). The purpose of this study is to develop a decision support and continuous monitoring system of the area by composing landslide hazard and risk maps. For that reason, several approaches of the weighted linear combination (WLC), a semi-quantitative hazard analysis method, were adopted in a Geographic Information Systems (GIS) environment. The results were validated using a pre-existing landslide database enriched with new landslide locations mapped through image interpretation of a processed IKONOS satellite image. The validation results showed that the WLC method coupled with remote sensing (RS) and GIS techniques can support engineering geological studies concerning landslide vulnerability of hazardous areas.