1,721,174 research outputs found
LASER SCANNER SURVEY TO REBUILD LARGE BOULDER ACCUMULATED BY EXTREME EVENT IN TORRE SQUILLACE (SOUTHERN APULIA - ITALY)
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The boulders berm of Punta Saguerra (Taranto, Italy): a morphological imprint of 4th April, 1836 Rossano Calabro tsunami?
No full textAn extended berm of calcarenitic boulders is recognisable at Punta Saguerra, a few kilometres south of Taranto (Apulia, Italy) while isolated boulders are sparse in other near localities. The berm is at 2-5 m above present sea level (a.p.s.l), on a rocky headland gently sloping toward the sea; it is separated from the coastline by a large terrace. A detailed study of its stratigraphy and its morphology has been performed in order to define its depositional mechanism; in particular, integrated DGPS and Laser Scanner surveys have provided precise details of each boulder: position, size and distance from the shoreline. The accumulation is constitute of boulders up to 30 tons, which locally are arranged in rows of embricated patterns. The surfaces of the biggest boulders are characterised by biogenic encrustations and by solution potholes that indicate their intertidal/adlittoral/spray zone provenience. Based on direct observations of each boulder (size, shape, weight and long axis azimuth), together with hydrodynamic equations it is possible to hypothesize the extreme event – geodynamic or meteorological – which was responsible for this singular accumulation. Together AMS age determination on Vermetid sp. sampled from boulder surfaces and chronicle data suggest that the accumulation may be attributed to the tsunami generated by the strong earthquake that occurred on April 24, 1836, the epicentre of which has been localised near Rossano Calabro, along the Ionian coast of northern Calabria
Evaluation of tsunami flooding using geomorphologic evidence
No full textWhatever the generating mechanism of a tsunami may be, this event can discharge destructive energy along coastal areas and produce widespread inundation. The presence of large boulders along rocky coasts could be a useful indicator to understand the extent of the impact of past tsunami floods. A detailed study of the deposited boulder features - size, shape and rock density and their initial position prior to the transport - is extremely important when reconstructing the possible morphodynamic scenario(s); applying the appropriate equations is important when aiming to assess the maximum extent of flooding. The integration of morphological and hydrodynamic data allows for an estimation of the water level during the tsunami event responsible for boulder transport. Moreover, it is possible to calculate how far the impacting wave flooded inland; this is a function of the wave parameters and of the degree of roughness of the flooded terrain that is expressed by the Manning number. To evaluate its probable/average value, experimental data, computer simulations and post-tsunami surveys have been performed in two sectors of the Southern Apulia coastline, characterised by the presence of tsunami boulder fields and/or ridges. The surveys in each site have allowed for the calculation of the boulder sizes, the estimation of their pre-transport location and the extent of inland flooding. Data have been processed using a Geographic Information System (GIS). As a result a flooding map, useful in planning future possible actions for coastal area use, has been produced. (C) 2009 Elsevier B.V. All rights reserved
Indicatori morfologici dell’impatto di eventi meteorologici estremi nella Puglia Meridionale
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