Skip to Main Content
Skip Nav Destination
GEOREF RECORD

Seismological constraints on the source mechanism of the damaging seismic event of 21 August 2017 on Ischia Island (southern Italy)

Thomas Braun, Daniela Famiani and 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 (September 2018) 89 (5): 1741-1749

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 M (sub w) 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 M (sub w) 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.


ISSN: 0895-0695
EISSN: 1938-2057
Serial Title: Seismological Research Letters
Serial Volume: 89
Serial Issue: 5
Title: Seismological constraints on the source mechanism of the damaging seismic event of 21 August 2017 on Ischia Island (southern Italy)
Affiliation: Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy
Pages: 1741-1749
Published: 201809
Text Language: English
Publisher: Seismological Society of America, El Cerrito, CA, United States
References: 42
Accession Number: 2019-005956
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
N40°42'00" - N40°46'60", E13°50'60" - E13°58'00"
Secondary Affiliation: GFZ German Research Center for Geosciences, DEU, Germany
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: 201906
Close Modal

or Create an Account

Close Modal
Close Modal