3D-Kernel Based Imaging of an Improved Estimation of (Qc) in the Northern Apulia (Southern Italy)

We investigate crustal seismic attenuation by the coda quality parameter (Qc) in the Gargano area (Southern Italy), using a recently released dataset composed of 191 small earthquakes (1.0 ≤ ML ≤ 2.8) recorded by the local OTRIONS and the Italian INGV seismic networks, over three years of seismic monitoring. Following the single back-scattering theoretical assumption, Qc was computed using different frequencies (in the range of 2–16 Hz) and different lapse times (from 10 to 40 s). The trend of Qc vs. frequency is the same as that observed in the adjacent Umbria-Marche region. Qc at 1 Hz varies between 11 and 63, indicating that the area is characterized by active tectonics, despite the absence of high-magnitude earthquakes in recent decades. The 3D mapping procedure, based on sensitivity kernels, revealed that the Gargano Promontory is characterized by very low and homogeneous Qc at low frequencies, and by high and heterogeneous Qc at high frequencies. The lateral variations of Qc at 12 Hz follow the trend of the Moho in this region and are in good agreement with other geophysical observations.

The computational work has been executed on the IT resources of the ReCaS- Bari data center, which have been made available by two projects financed by the MIUR (Italian Ministry for Education, University and Re-search) in the “PON Ricerca e Competitività 2007–2013” Program: ReCaS (Azione I-Interventi di rafforzamento strutturale, PONa3_00052, Avviso 254/Ric) and PRISMA (Asse II-Sostegno all’innovazione, PON04a2_A).

References
Author Contributions: Conceptualization, M.F., E.D.P., S.d.L., G.P. and A.T.; data curation, S.L.; formal analysis, M.F., S.L., E.D.P. and S.d.L.; funding acquisition, E.D.P. and A.T.; methodology, M.F., E.D.P. and S.d.L.; project administration, A.T.; resources, E.D.P. and A.T.; software, S.L. and E.D.P.; supervision, M.F., E.D.P., S.d.L., G.P. and A.T.; validation, M.F., E.D.P. and S.d.L.; visualization, M.F.; writing—original draft, M.F., E.D.P. and S.d.L.; writing—review and editing, M.F., S.L., E.D.P., S.d.L., G.P. and A.T. All authors have read and agreed to the published version of the manuscript.
Funding: This work was partially supported by Project PRIN n. 201743P29 FLUIDS (Detection and tracking of crustal fluid by multi-parametric methodologies and technologies). E.D.P. was partially funded by the Spanish Mineco Project FEMALE, PID2019-106260GB-I00.
Data Availability Statement: Envelope data used in this study are described in the data paper Filippucci et al. 2021 (submitted to Data MDPI). Data are available online on Mendeley repository: http://dx.doi.org/10.17632/w9hsj2whzm.1.
Acknowledgments: The computational work has been executed on the IT resources of the ReCaS- Bari data center, which have been made available by two projects financed by the MIUR (Italian Ministry for Education, University and Re-search) in the “PON Ricerca e Competitività 2007–2013” Program: ReCaS (Azione I-Interventi di rafforzamento strutturale, PONa3_00052, Avviso 254/Ric) and PRISMA (Asse II-Sostegno all’innovazione, PON04a2_A). We thank an anonymous reviewer for the suggestion about the plot of Qc(r).
Conflicts of Interest: The authors declare no conflict of interest.
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