Abstract
<p>A Chirp sub-bottom sonar investigation was performed in the 150 km<sup>2</sup> wideAugustaBasin, located in the eastern Sicily Ionian coast, a region repeatedly hit by strong earthquakes in historical time, with the end of identifying possible evidence of active tectonics. Seismostratigraphy shows two main reflectors: R1, formed between 60 ka and 19 ka BP, and R2 that is the top of the Holocene deposits. Morphobathymetry reveals two marine abrasion surfaces, Ms1 and Ms2 that are related to the 35 ka and 25 ka BP marine high stills, respectively. This study highlights that R1 and the onlapping Holocene sediments are affected by normal and probably strike-slip faulting. A set of NE-SW striking normal faults represents the oldest system, because they dislocate R1 but not the Holocene deposit. NNW-SSE striking extensional faults show more recent activity since they displace Ms2, the Holocene sequence and cause seafloor up-warping. NE-SW normal faults produce asymmetric basins where the Holocene deposits form wedged bodies. ENE-WSW left-lateral faults dissect a paleo-island, Ms2 and the NNW-SSE fault system. Moreover, seismically induced slumps involving the Holocene sediments, are found at the foot of some fault scarps. The presence of slumped bodies and active faults indicates ongoing deformation in the basin. Identified active faults are consistent with the main regional Malta Escarpment fault system, of which they can be considered as the incipient westernmost extension. This study supports the hypothesis that the Malta Escarpment is active and can be responsible for the regional seismicity.</p>
Highlights
The coastal area of south eastern Sicily experienced several large magnitude earthquakes and tsunamis in pre-instrumental times (Figure 1) [CPTI Working Group 2004]
The location of the historical earthquakes is only based on macroseismic data and Pleistocene-Holocene evidence for tectonic activity of the region reported in the geological literature is limited and ambiguous
This work focuses on the Augusta Basin (Figure 1), located in the Ionian offshore, north-east of the Hyblean Foreland, which is considered a key area to clarify the seismotectonic setting of eastern Sicily
Summary
The coastal area of south eastern Sicily experienced several large magnitude earthquakes and tsunamis in pre-instrumental times (Figure 1) [CPTI Working Group 2004]. The location of the historical earthquakes is only based on macroseismic data and Pleistocene-Holocene evidence for tectonic activity of the region reported in the geological literature is limited and ambiguous. This work focuses on the Augusta Basin (Figure 1), located in the Ionian offshore, north-east of the Hyblean Foreland, which is considered a key area to clarify the seismotectonic setting of eastern Sicily. For this reason, we performed a geophysical survey using highresolution sub-bottom Chirp techniques, which are suited to this kind of study. Chirp sub-bottom analysis performed in several basins worldwide has highlighted submarine slides, soft sediment deforma-
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