EGU2020-10847
https://doi.org/10.5194/egusphere-egu2020-10847
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

High Resolution Attenuation Images From Active Seismic Data: The Case Study of Solfatara Volcano (Southern Italy)

Guido Russo1, Vincenzo Serlenga2, Grazia De Landro1, Ortensia Amoroso3, Gaetano Festa1, and Aldo Zollo1
Guido Russo et al.
  • 1Università di Napoli "Federico II", Dept. of Physics "E. Pancini", Napoli, Italy
  • 2CNR, Istituto di Metodologie per l'Analisi Ambientale, Tito Scalo, Italy
  • 3Università di Salerno, Dept. of Physics "E. Caianiello", Fisciano, Italy

The anelastic attenuation of rocks strongly depends on the contained fluid physical state and saturation. Furthermore, it is more sensitive than elastic parameters to changes in the physical state of materials. In a geologically complex  volcanic context, where fluids play a very important role, anelastic imaging of the subsoil is therefore a very powerful tool for a better understanding of its dynamics.

In this study we present a robust workflow aimed at retrieve accurate 1-D and 3-D anelastic models from the processing of active seismic data, in terms of lateral and depth variations of P-wave quality factors QP. This methodology has been applied to data collected during a high resolution active seismic experiment in a very small-scale volcanic volume, the Solfatara crater, within Campi Flegri caldera, Southern Italy. The presented methodology is developed in three distinct steps: 1) the active seismic data have been properly processed and analyzed for measuring the t* attenuation parameter for all possible source-receivers couples. First, the source contribution has been removed by cross-correlating the recorded signal with the sweep function of the Vibroseis, which was the adopted active seismic source. Then, the spectral decay method has been applied in order to compute the t* values. 2) A reference 1-D attenuation model has been retrieved by means of a grid search procedure aiming at finding the 1-D Qp structure that minimizes the residual between the average observed t* and the theoretical t* distributions. The obtained starting reference model allowed to build a preliminary map of t* residuals through which the retrieved t* dataset has been validated. 3) The 15,296 t* measurements have been inverted by means of a linearized, perturbative approach, in a 160 x 160 x 45 m3 tomographic grid.

The retrieved 3-D attenuation model describes the first 30 m depths of Solfatara volcano as composed of very high attenuating materials, with Qp values ranging between 5 and 40. The very low Qp values, correlated with low Vp values retrieved by a previous tomographic work carried out in the area, indicate the low consolidation degree of very superficial volcanic materials of Solfatara volcano. Finally, in the NE part of the crater, lower attenuating bodies have been imaged: it is a further hint for characterizing this area of the volcano as the shallow release of the CO2 plume through the main fumaroles of the crater.

How to cite: Russo, G., Serlenga, V., De Landro, G., Amoroso, O., Festa, G., and Zollo, A.: High Resolution Attenuation Images From Active Seismic Data: The Case Study of Solfatara Volcano (Southern Italy), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10847, https://doi.org/10.5194/egusphere-egu2020-10847, 2020

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Presentation version 2 – uploaded on 01 May 2020
Version description: This version includes a brief initial summary of the work in the few first slides, than the work is presented in details.[...]
  • CC1: Comment on EGU2020-10847, Luca De Siena, 04 May 2020

    Hi and thanks for submitting abstract and presentation!

    What is the difference between this work and that of 2017 (Scientific Reports)? What about applying one of those coda-imaging approaches that we developed?

    All the best,

    Luca

    • AC1: Reply to CC1, Vincenzo Serlenga, 04 May 2020

      Dear Luca,

      thank you for your comment.

      Well, De Landro et al., 2017 (SR) provided a tomographic Vp model from the inversion of travel time data. Here, we inverted t* measured on the same dataset, in order to retrieve a preliminar 3-D Qp model. The active seismic dataset still belongs to RICEN experiment, but the purpose is different.

      What about the coda method? Well, it could be interesting, also because in a so shallow environment the scattering may have a very important role.  But, to date, we are not so familiar with the method. On the other hand, the t* approach allowed us to obtain a first image of the intrinsic anelastic properties of the subsoil.

      Thank you again, 

      Vincenzo

      • CC2: Reply to AC1, Luca De Siena, 04 May 2020

        Thanks Vincenzo,

        I will keep other questions for the chat as I will be chairing during your presentation. However, if the data are available, we can have a chat about applying MuRAT to the dataset?

        See you tomorrow (online),

        Luca

  • CC3: Comment on EGU2020-10847, Konradin Weber, 05 May 2020

    How is this compared with groundbased measurements?

    • AC2: Reply to CC3, Vincenzo Serlenga, 05 May 2020

      Hi Konradin, 

      thank you for your comment.

      The work here presented is strictly related to De Landro et al., (2017) (DOI:10.1038/s41598-017-03604-0), where we described the 3-D velocity model of Solfatara Volcano. Well, in that work we also correlated the elastic images with other observables. Among these, both temperature and COflux measurements. If you look at figure 4 of that paper you can clearly observe high values both in temperature and in CO2 flux in the northeastern part of the investigated area. In the present work, in this part of Solfatara, we also found, at about 25 m depth, high Qp values, which may be interpreted, based on laboratory study by Ito et al. (1979) (doi: 10.1029/JB084iB09p04731) as the effect of presence of gas. Therefore, this attenuation featuremay may be reliably related to groundbased measurements. 

      Best regards,

      Vincenzo

Presentation version 1 – uploaded on 28 Apr 2020 , no comments