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The 21 August 2017 M (sub d) 4.0 Casamicciola earthquake; first evidence of coseismic normal surface faulting at the Ischia volcanic island

Rosa Nappi, Giuliana Alessio, Germana Gaudiosi, Rosella Nave, Enrica Marotta, Valeria Siniscalchi, Riccardo Civico, Luca Pizzimenti, Rosario Peluso, Pasquale Belviso and Sabina Porfido
The 21 August 2017 M (sub d) 4.0 Casamicciola earthquake; first evidence of coseismic normal surface faulting at the Ischia volcanic island
Seismological Research Letters (June 2018) 89 (4): 1323-1334

Abstract

On 21 August 2017, a shallow earthquake of Md 4.0 struck the Casamicciola Terme village in the north of Ischia volcanic island (Italy). It caused two fatalities and heavy damage in a restricted area of a few square kilometers. Casamicciola Terme has been recurrently destroyed in the last centuries by similar volcano-tectonic earthquakes (1762, 1767, 1796, 1828, 1881, and 1883). After the catastrophic 1883 Casamicciola event (2343 casualties), this is the first heavy damaging earthquake at Ischia that provides, for the first time, the opportunity of integrating historical seismicity, macroseismic observations, instrumental information, and detailed mapping of coseismic geological effects. Soon after the 2017 mainshock we surveyed the epicentral area to collect data on the coseismic ground effects, recording more than 100 geological field observations. Mapped effects define a belt which closely follows the trace of the Casamicciola E-W-trending normal fault system, bounding the northern slope of Mt. Epomeo, previously known as a Latest Pleistocene to Holocene normal fault with a slip rate of approximately 3.0 cm/yr. We found significant evidence for coseismic surface faulting, testified by a main alignment of ruptures for a 2 km end-to-end length and normal dip-slip displacement of 1-3 cm. The geometry and regularity of the structural pattern, together with constant kinematics of the coseismic ruptures with the north side down, strongly suggest a primary tectonic origin for the mapped ruptures and strongly supports an E-W normal-faulting focal mechanism for the 2017 Casamicciola earthquake. Macroseismic information supports the notion that previous historical events also had a similar style of faulting.


ISSN: 0895-0695
EISSN: 1938-2057
Serial Title: Seismological Research Letters
Serial Volume: 89
Serial Issue: 4
Title: The 21 August 2017 M (sub d) 4.0 Casamicciola earthquake; first evidence of coseismic normal surface faulting at the Ischia volcanic island
Affiliation: Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Napoli, Osservatorio Vesuviano Italy, Naples, Italy
Pages: 1323-1334
Published: 20180613
Text Language: English
Publisher: Seismological Society of America, El Cerrito, CA, United States
References: 59
Accession Number: 2018-057725
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table, sketch maps
N40°42'00" - N40°46'60", E13°50'60" - E13°58'00"
Secondary Affiliation: Istituto Ambiente Marino e Costiero, ITA, Italy
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201831
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