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Seismological Constraints on the Source Mechanism of the Damaging Seismic Event of 21 August 2017 on Ischia Island (Southern Italy)

2018; Seismological Society of America; Volume: 89; Issue: 5 Linguagem: Inglês

10.1785/0220170274

1938-2057

Thomas Braun, Daniela Famiani, Simone Cesca,

Seismic Performance and Analysis

Research Article| July 11, 2018 Seismological Constraints on the Source Mechanism of the Damaging Seismic Event of 21 August 2017 on Ischia Island (Southern Italy) Thomas Braun; Thomas Braun aIstituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma1, Via di Vigna Murata, 605, 00143 Rome, Italy, thomas.braun@ingv.itdaniela.famiani@ingv.itcAlso at Seismological Observatory, Via Francesco Redi 13, 52100 Arezzo, Italy. Search for other works by this author on: GSW Google Scholar Daniela Famiani; Daniela Famiani aIstituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma1, Via di Vigna Murata, 605, 00143 Rome, Italy, thomas.braun@ingv.itdaniela.famiani@ingv.it Search for other works by this author on: GSW Google Scholar Simone Cesca Simone Cesca bGFZ German Research Center for Geosciences, Telegrafenberg, D‐14473 Potsdam, Germany, simone.cesca@gfz-potsdam.de Search for other works by this author on: GSW Google Scholar Author and Article Information Thomas Braun aIstituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma1, Via di Vigna Murata, 605, 00143 Rome, Italy, thomas.braun@ingv.itdaniela.famiani@ingv.itcAlso at Seismological Observatory, Via Francesco Redi 13, 52100 Arezzo, Italy. Daniela Famiani aIstituto Nazionale di Geofisica e Vulcanologia, Sezione di Roma1, Via di Vigna Murata, 605, 00143 Rome, Italy, thomas.braun@ingv.itdaniela.famiani@ingv.it Simone Cesca bGFZ German Research Center for Geosciences, Telegrafenberg, D‐14473 Potsdam, Germany, simone.cesca@gfz-potsdam.de Publisher: Seismological Society of America First Online: 11 Jul 2018 Online Issn: 1938-2057 Print Issn: 0895-0695 © Seismological Society of America Seismological Research Letters (2018) 89 (5): 1741–1749. https://doi.org/10.1785/0220170274 Article history First Online: 11 Jul 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Thomas Braun, Daniela Famiani, Simone Cesca; Seismological Constraints on the Source Mechanism of the Damaging Seismic Event of 21 August 2017 on Ischia Island (Southern Italy). Seismological Research Letters 2018;; 89 (5): 1741–1749. doi: https://doi.org/10.1785/0220170274 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search ABSTRACT On 21 August 2017, an MD 4.0 earthquake struck Ischia island in the Tyrrhenian Sea off the coast of Naples, Italy. In spite of its modest magnitude, the earthquake caused two deaths and severe building damage on the northern side of the island. Initial hypocenter locations based on arrival times were highly uncertain and several proposed moment tensor solutions were inconsistent. These contradictory observations prompted a new calculation of the earthquake parameters using alternative methods. Our new approach, based on the determination of P‐wave particle motion, evaluation of rotated spectra, and accurate calculation of S‐minus‐P travel time, yields a hypocentral depth of 2 km and a location in the same area as the devastating seismic event that struck Ischia in 1883. We invert the moment tensor for a best‐fitting double couple (DC), obtaining an Mw 3.9 with a normal mechanism and an optimal depth of 8 km. Calculation of the full moment tensor results in (1) 36% negative isotropic component and 26% negative compensated linear vector dipole (CLVD) components, (2) a better fit at a shallower source depth than for the corresponding DC, and (3) a magnitude estimate of Mw 4.1. Modeling of the waveform and the first motion recorded in Ischia's station IOCA predicts, however, a negative polarity, which is in disagreement with the observation. We therefore suggest a complex rupture process, with an initial shallow normal‐faulting event that triggered a subsequent shallow underground collapse. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.