1,721,079 research outputs found
Multi-seismic cycle deformation rates from Holocene normal fault scarps on Crete (Greece).
No full textMorphotectonic features reveal recent seismic activity on normal faults on Crete allowing slip-rates, palaeoearthquake magnitudes and earthquake recurrence intervals to be inferred. The studied faults show major escarpments (100s m high, 10s km long), separating uplifted Mesozoic rocks from Quaternary deposits. During Holocene, slip-rates out-paced erosion/sedimentation rates and 5-15 m high fresh scarps formed at the base of the major escarpments. Based on our field observations and following empirical relationships between magnitude, surface rupture length and maximum co-seismic vertical displacement, it was possible to infer all principal seismotectonic parameters for the investigated faults. Long-term throw-rates range between 0.4 and 1.2 mm/a, maximum expected magnitudes between 6.3 and 6.6 (or 6.6-6.9, considering the worst case scenario), while mean recurrence intervals range between >200 and 1000 years. These estimates are in good agreement with the historical and instrumental seismicity allowing to improve seismic hazard estimates in Crete
Active thrust tectonics in western Sicily (southern Italy): the 1968 Belice earthquake sequence
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Large boulder deposits by tsunami waves along the Ionian coast of south-eastern Sicily (Italy)
No full textThe Ionian coast of south-eastern Sicily, between the towns of Augusta and Siracusa, is characterized by the occurrence of anomalous calcareous boulders. They are mostly scattered along large terraces located 2-5 m above sea level, gently sloping towards the sea. Boulders are up to 182 t in weight and are arranged either in isolated elements or small groups composed of a few stacked elements. Several boulders show biogenic encrustations (serpulids, balanids, lithophaga) all over their surface which suggest that they were dragged from the mid-sublittoral zone. Other boulders are partially covered by biogenic encrustations and show morphological features (karstic pools, exposed fracture surfaces) suggesting that they were detached and scattered from the mid-supralittoral zone. Direct observations on each boulder (distance from the shoreline, size and weight), together with statistical analysis of the storm regime of the area, allowed to operate hydrodynamic estimations useful to verify if tsunami or storm waves were responsible for their detachment and transport, while radiocarbon age determinations on marine organisms constrained the timing. Collected data, compared to historical catalogues, suggest that in the last 1000 years three seismic events with local sources could have triggered tsunami waves associated with the boulder deposits occurring in the area. The first two were probably triggered by the earthquakes of February 4, 1169 and January 11, 1693 which destroyed south-eastern Sicily. According to geological data and numerical modelling, the seismogenic source could be located in the Ionian offshore between Catania and Siracusa. The third tsunami was generated by the strong earthquake which took place in the Strait of Messina on December 28, 1908. © 2007 Elsevier B.V. All rights reserved
Late Neogene to Quaternary contractional structures in Crete (Greece).
No full textBased on geological and tectonic investigations carried out along an N–S coast-to-coast transect across central Crete, southern Aegean (Greece), new meso- and macro-structural data mainly collected from Neogene–Quaternary deposits are presented and discussed. The occurrence of large-scale folds and thrusts together with diffuse minor contractional structures, as well as the overall geometry of the fault-bounded sedimentary basins document the persistence of a Tortonian–Early Pleistocene contractional regime, characterized by an NNW–SSE to NNE–SSW shortening direction and affecting the upper crust. This contractional event(s) was associated with the ongoing Hellenic subduction and caused the development of a southwards migrating out-of-sequence thrust system consisting of both reactivated inherited structures and new ones. The new data emphasize the importance and the extent of this contractional event intervening between the Early–Middle Miocene exhumation phase and the still active upper crustal extensional regime that was resumed in the island only during Pleistocene when the region was affected by diffuse normal faulting. While the contractional event was likely due to a stronger coupling along the overall subduction system, the onset of the new extensional stress conditions was probably related to a sudden southwards jump of the basal detachment along the lithospheric African subduction that caused a general stress release in the uppermost crust
Neogene geodynamic evolution of the Calabrian Arc: open problems and relation with Southern Tyrrenian Sea
No full textThe use of morphotectonic data to infer seimotectonic parameters of normal faults in Crete, Greece.
No full textEvidenze di processi deformativi continui e tettonica trascorrente nel Cnale di Sicilia: le Isole Maltesi.
No full textIn this paper we report the results of a study concerning the macro and meso-structures affecting the oligo-miocene succession and a few quaternary deposits
outcropping in the maltese islands. Data analysis allowed us to define in detail the geo-structural setting of the
study area and to put in evidence the mode of deformation responsible for its generation. The main conclusions that can be drawn indicate that the area in question has been affected by a progressive deformative
process during which it is possible to isolate a series of
tectonic events that are characterized by different geometries of the stress field. The above information
together with available data relative to the surrounding
regions (Tunisia, Pelagian block and Pantelleria) also
made it possible to discuss in detail the temporal relations among the deformative events with the aim of obtaining a better understanding of the neotectonic evolution of the whole sector located between the undeformed african continental margin and the Sicilian maghrebide chain
Holocene normal faulting in Crete (Greece): insights for the regional seismotectonic behaviour.
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