DOI: 10.13127/styrr_fm/2000-2021
title: Focal Mechanisms in southern Tyrrhenian Sea and northern Sicily between 1 January 2000 and 31 August 2021 (STyrr_FM_2000-2021)
title: STyrr_FM_2000-2021

description: We computed new 268 focal mechanisms (1.3≤M≤4.6), with rays traced through the 3D velocity model of Scarfì et al. 2018, of events occurred in the southern Tyrrhenian Sea and northern Sicily between 1 January 2000 and 31 August 2021. The earthquakes were recorded by the land seismic network managed by the INGV and a seafloor network, consisting of 14 Ocean Bottom Seismometers and Hydrophones, deployed during the Tyrrhenian Deep sea Experiment (TYDE, December 2000 – May 2001; Dahm et al., 2002; Sgroi et al., 2006) and the NEMO-SN1 seafloor observatory (October 2002 – February 2003; June 2012 - June 2013; Sgroi et al. 2021).
description: Abbiamo calcolato nuovi 268 meccanismi focali (1.3 ≤ M ≤4.6), con raggi tracciati attraverso il modello di velocità 3D di Scarfì et al. 2018, degli eventi avvenuti nel Mar Tirreno meridionale e nel settore settentrionale della Sicilia tra il 1° gennaio 2000 e il 31 agosto 2021. I terremoti sono stati registrati dalla rete sismica terrestre gestita dall’INGV e da una rete sottomarina, composta da 14 sismometri e idrofoni di fondale oceanico, installati durante il Tyrrhenian Deep Sea Experiment (TYDE, dicembre 2000 – maggio 2001; Dahm et al., 2002; Sgroi et al., 2006) e dall’osservatorio sottomarino NEMO-SN1 (ottobre 2002 – febbraio 2003; giugno 2012 – giugno 2013; Sgroi et al., 2021).
description: We collected basic data (travel times and first polarities) from available datasets (ISIDe Working Group, 2007) and published studies (Sgroi et al., 2006; Barberi et al., 2006; Monna et al., 2013). Then we processed them using the 3D velocity model of Scarfì et al. (2018) and the tomoDDPS algorithm (Zhang et al., 2009). This software has the advantage of using a combination of both absolute and differential arrival times, so that for earthquakes with closely spaced foci, travel times errors due to inaccurate velocity models in the volume outside the cluster will essentially be cancelled. By using FPFIT software (Reasenberg and Oppenheimer, 1985), we obtained 268 focal solutions with an average uncertainty on the orientation of the nodal planes of about 10°. These focal mechanisms can be considered representative of the kinematics characterising the southern Tyrrhenian Sea and the northern Sicily, since they are distributed in all the main seismogenically active areas of the region.
description: The table (STyrr_FM_2000-2021) shows focal parameters of the analysed earthquakes. Specifically: ID = identification number; Date (year/month/day); O.T. = Origin Time (hour, minute, second and cent); Lat = latitude north in degrees; Long = longitude east in degrees; Depth in km; MagType = duration (Md), local (ML) or moment magnitude (Mw); Magnitude; Npol = number of polarities; Plane 1 (STRK, DIP, RAKE), Plane 2 (STRK, DIP, RAKE) = strike, dip and rake of the first and second nodal planes; P-Axis (AZM, PLNG), T-Axis (AZM, PLNG) = azimuth and plunge of the P- and T-axes; Q = quality of the focal mechanism (2 = best quality; 1 = medium quality; 0 = low quality); Cat = category of the focal mechanism (NF = normal fault, NS = normal-strike, SS = strike-slip, TF = thrust fault, TS = thrust-strike, HV = horizontal-vertical).