Daljinska istraživanja kao preliminarna metoda za otkrivanje aktivnih tektonskih struktura: primjer albanskog orogena

As is well known, both the traditional direct geological and geophysical survey methods used to identify geologic features are very expensive and time-consuming procedures. In this regard, remote sensing methods applied to multispectral and medium spatial resolution satellite images allow a more focused approach with respect to the more specific geologic methods. This is achieved by a preliminary land inspection carried out by the semi-automated analysis of satellite imagery. This avoids wasting resources as the geological/geophysical survey methods can be later applied only to those zones suspected of having certain tectonic activity (derived by the remotely sensed imagery). This paper will evaluate an ASTER sensor satellite image (and its derived Digital Elevation Model or DEM), in order to point out the suspected presence of active geologic structures (faults). The area in question is west – central Albania. The results of the remote sensing procedures are later compared with the established data for the same area taken by satellite images, in order to verify the reliability of the adopted method. The source of the established data has been from the bibliography.Tradicionalne izravne geološke i geofizičke metode istraživanja koje se koriste za prepoznavanje geoloških obilježja su vrlo skupe i dugotrajne. U tom smislu metode daljinskh istraživanja za analizu multispektralnih satelitskih snimaka i snimaka srednje rezolucije omogućuju kvalitetniji pristup s obzirom na specifične geološke metode. U skladu s tim moguće je napraviti preliminarnu analizu površine tla putem poluautomatske analize satelitskih snimaka. Ovakva analiza omogućuje snižavanje troškova na način da se geološke/geofizičke metode istraživanja koriste naknadno, i to u onim područjima za koje se ovakvom analizom (korištenjem daljinskih snimaka) utvrdi postojanje određene tektonske aktivnosti. U ovom radu analizira se satelitska snimka ASTER (i na temelju nje napravljen digitalni model reljefa – DMR) kako bi se uputilo na eventualnu prisutnost aktivnih geoloških struktura (rasjeda). Ovim istraživanjem obuhvaćeno je područje zapadne i središnje Albanije. Radi utvrđivanja pouzdanosti navedene metode rezultati analize snimaka dobivenih daljinskim istraživanjem su uspoređeni s postojećim podacima za isto područje dobivenima satelitskim snimanjem. Postojeći, istraživanjima potvrđeni podaci preuzeti su iz objavljene literature

Palaeo-Shoreline Configuration of the Adventure Plateau (Sicilian Channel) at the Last Glacial Maximum

The Adventure Plateau, located in the NW sector of the Sicilian Channel, experienced several episodes of exposure/erosion and subsequent drowning, with the most recent occurring after the Last Glacial Maximum (LGM). Unlike other parts of the Sicilian Channel, the Adventure Plateau is relatively tectonically stable and is therefore best suitable for reconstructing its coastal configuration before the post-LGM marine transgression. Here, we use high-resolution seismic data to identify and map the palaeo-coastline at the LGM on the basis of the internal architecture of the prograding wedges (i.e., the location of the subaqueous clinoform rollover point) and the erosional markers such as the subaerial unconformities and the wave ravinement surfaces. These data, which show an extreme variability in the palaeo-morphology of the coastal margins of the Adventure Plateau, have been complemented with vintage seismic profiles in order to entirely cover its perimeter. The mapped LGM coastline has then been compared to predictions from glacial isostatic adjustment (GIA) modeling, which considers the horizontal migration of the shorelines in response to sea level rise and to Earth's rotational and deformational effects associated with deglaciation. The two shorelines (i.e., the coastline derived from the marine data interpretation and the one derived from the GIA model) are in good agreement at 21 kyears BP, although some discrepancies occur in the southern part of the plateau, where the seabed slope is extremely gentle, which makes the clinoform rollover points and the buried erosional unconformities difficult to detect. After 20 kyears BP, an acceleration in the rate of the sea level rise occurred. The results of this study indicate the importance of comparing experimental data with model predictions in order to refine and calibrate boundary parameters and to gain a better picture of the evolution of sea level rise over various time scales

Unraveling Past Submarine Eruptions by Dating Lapilli Tuff-Encrusting Coralligenous (Actea Volcano, NW Sicilian Channel)

none7noThe dating of young submarine volcanic eruptions, with their potential generation of tsunamigenic waves, is essential for a reliable hazard assessment. This is particularly relevant in highly populated coastal areas. The scarce knowledge of the underwater environment makes however, this reconstruction challenging. Our study is focused on the NW sector of the Sicilian Channel, where several small- and medium-size volcanic edifices are present. The only documented Surtseyan-type eruption occurred in A.D. 1831, forming the ephemeral Ferdinandea Island. Late Pleistocene to mid-Holocene eruptions have been up to now only hypothesized, and based solely on indirect data. Here we present the first radiocarbon dates of a coralligenous bioconstruction sampled at 34 m water depth from the summit of the Actea volcano, grown up progressively (up to nowadays) on a lapilli tuff deposit. Actea volcano is a recently discovered pyroclastic cone located at only four nautical miles off the SW coast of Sicily. The oldest age of the bioconstructions that started to encrustate the shallow water pyroclastics shortly after their emplacement (7,387 ± 175 cal years B.P.) represents a terminus ante quem, thus testifying a mid-Holocene submarine eruption in this sector of the Sicilian Channel. This method may be effectively used to bridge the gap between historical accounts and the geological record and thus may contribute to a better volcanic hazard assessment of submarine eruption and related phenomena such as tsunamis.openLodolo E.; Renzulli A.; Cerrano C.; Calcinai B.; Civile D.; Quarta G.; Calcagnile L.Lodolo, E.; Renzulli, A.; Cerrano, C.; Calcinai, B.; Civile, D.; Quarta, G.; Calcagnile, L

Late Quaternary transgressions and regressions in the Trieste Gulf (northeastern Adriatic Sea)

The integration of high-resolution seismic profiles, core data and radiocarbon plus U-Th datings, allows to document the late Quaternary succession of the Trieste Gulf, which represents the easternmost part of the northern Adriatic Sea. This succession consists of an alternation of shallow marine and continental deposits organized to compose four transgressive-regressive sequences down to ca. 90 m below present sea level. The sequences terminate landwards against a stepped surface bounding the Eocene Trieste Flysch and produced by alternating episodes of wave erosion during transgressions and subaerial exposure during stages of relative sea-level fall and lowstand. Two shallow-marine wedges, in addition to the Holocene one, have been recognized; they are associated with the Marine Isotopic Stage (MIS) 5.5 (Tyrrhenian) and probably at least one of the peaks of MIS 7. The recognized shallow-marine wedges typically prograde just seaward of a buried wave-cut platform lying in front of a receding paleo-coastal cliff. A previously unrecognized stratigraphic hiatus of ca. 25 ka duration, containing the whole Last Glacial Maximum (LGM) phase, was found at the top of palustrine deposits that accumulated on the MIS 5.5 marine sediments until ca. 40 cal ka B.P. and a post-LGM peat bed accumulated during the Younger Dryas stadial. The beginning of the Holocene was characterized by marked fluvial aggradation preceding the marine transgression at ca. 11-10 cal ka B.P. This new evidence is invaluable for better understanding late Quaternary sedimentary and erosional episodes that characterized the easternmost part of the norther Adriatic Sea, in the frame of the well-known glacio-eustatic sea-level changes

Seismic hazard for the Trans Adriatic Pipeline (TAP). Part 2: broadband scenarios at the Fier Compressor Station (Albania)

AbstractTo ensure environmental and public safety, critical facilities require rigorous seismic hazard analysis to define seismic input for their design. We consider the case of the Trans Adriatic Pipeline (TAP), which is a pipeline that transports natural gas from the Caspian Sea to southern Italy, crossing active faults and areas characterized by high seismicity levels. For this pipeline, we develop a Probabilistic Seismic Hazard Assessment (PSHA) for the broader area, and, for the selected critical sites, we perform deterministic seismic hazard assessment (DSHA), by calculating shaking scenarios that account for the physics of the source, propagation, and site effects. This paper presents a DSHA for a compressor station located at Fier, along the Albanian coastal region. Considering the location of the most hazardous faults in the study site, revealed by the PSHA disaggregation, we model the ground motion for two different scenarios to simulate the worst-case scenario for this compressor station. We compute broadband waveforms for receivers on soft soils by applying specific transfer functions estimated from the available geotechnical data for the Fier area. The simulations reproduce the variability observed in the ground motion recorded in the near-earthquake source. The vertical ground motion is strong for receivers placed above the rupture areas and should not be ignored in seismic designs; furthermore, our vertical simulations reproduce the displacement and the static offset of the ground motion highlighted in recent studies. This observation confirms the importance of the DSHA analysis in defining the expected pipeline damage functions and permanent soil deformations

Remote sensing as a preliminary analysis for the detection of active tectonic structures: an application to the Albanian orogenic system

As is well known, both the traditional direct geological and geophysical survey methods used to identify geologic features are very expensive and time-consuming procedures. In this regard, remote sensing methods applied to multispectral and medium spatial resolution satellite images allow a more focused approach with respect to the more specific geologic methods. This is achieved by a preliminary land inspection carried out by the semi-automated analysis of satellite imagery. This avoids wasting resources as the geological/geophysical survey methods can be later applied only to those zones suspected of having certain tectonic activity (derived by the remotely sensed imagery). This paper will evaluate an ASTER sensor satellite image (and its derived Digital Elevation Model or DEM), in order to point out the suspected presence of active geologic structures (faults). The area in question is west – central Albania. The results of the remote sensing procedures are later compared with the established data for the same area taken by satellite images, in order to verify the reliability of the adopted method. The source of the established data has been from the bibliography

Geology of the Pergola–Melandro basin area, Southern Apennines, Italy

The Southern Apennines (SA) are part of the Apennine–Maghrebian chain, a segment of the circum-Mediterranean Alpine orogenic system. It is a NE-verging fold-and-thrust belt with an about N150°-striking axis developed since the late Oligocene-early Miocene. The Geological Map at 1:25,000 scale of the Pergola–Melandro basin area, presents a sector of the axial zone of the SA which represents a key area to reconstruct the tectonic evolution of this chain. The map describes the complex structural and stratigraphic relationships between the three main tectonic units forming this sector of the SA: (1) the carbonate slope succession of the Maddalena Mts Unit, interpreted as the eastern boundary of the Apennine carbonate Platform; (2) the Lagonegro Unit, resulting from the deformation of the homonym pelagic basin; (3) the strongly deformed Argille Variegate Group sandwiched between the two previous units. Three main contractional tectonic stages, occurring from middle Miocene to Pliocene, have been recognized. Since Pliocene times low-angle extensional tectonic contacts and tectono-gravitative detachments affected the tectonic pile

A Failed Rift in the Eastern Adventure Plateau (Sicilian Channel, Central Mediterranean)

Widespread volcanism has been known in the Sicilian Channel for a long time, even if some submarine volcanoes have only recently been discovered. Most of this volcanism formed along the NNE-trending transfer zone known as the Capo Granitola–Sciacca Fault Zone, while others, such as the islands of Pantelleria and Linosa, are associated with the continental rift zone that has developed since the early Pliocene in the central part of the Sicilian Channel through the formation of three deep tectonic troughs (Pantelleria, Linosa and Malta). However, the origin of a group of five volcanoes (here called “Tetide volcanic cluster”) that form a NW-SE alignment on the eastern edge of the Adventure Plateau is not yet known. In this work, we hypothesize that this volcanic alignment may represent the remnants of a failed rift attempt that was unable to generate another tectonic trough in the Sicilian Channel. Based on seismic sections and gravimetric data, three phases in the formation of this volcanic alignment can be identified: (i) a major magmatic intrusion in the early Pliocene associated with a NW-SE normal fault that formed during the opening of the Pantelleria graben, leading to the uplift and deformation of the host sedimentary rocks; (ii) a late Pliocene-Quaternary tectono-magmatic quiescent phase; and (iii) a renewed magma intrusion through fissures or cracks that led to the formation of the volcanoes in the late Quaternary. This process was not able to cause significant extension and only limited volcanism, which is why the “Tetide volcanic cluster“ is interpreted as the morphological expression of a failed rift