GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 In this study, different from the previous application where only standard seismic stations of the seismological network were considered, we applied the MLTWA to seismograms recorded by a vertical array of sensors installed in a borehole and on buildings. The observed seismic energy integrals are inverted, considering a layered medium to obtain the best scattering and intrinsic attenuation coefficients. Since the application of MLTWA, when considering a layered medium, might become computationally demanding, we chose an inversion strategy made by the combination of a grid search over a large range of possible values but with a relatively large grid spacing of seismic albedo (i.e., the ratio between the scattering loss and the total energy loss ) and extinction length (i.e., the distance over which the primary S-wave energy is decreased by 1/e). Finally, once identified using the grid search, the area with a potential global minimum of the solution, the inversion is again carried out, employing a simulated annealing algorithm Kirkpatrick (1983). The method is applied to data collected from an array of sensors installed in a borehole and on a nearby building at Atakoy test site, Istanbul,Turkey. The results are compared with those of previous studies of attenuation estimated with the independent geophysical method for the investigated vertical array. References Aki, K. (1969). “Analysis of the seismic coda of local earthquakes as scattered waves”. In: Journal of geophysical research 74.2, pp. 615–631. Fehler, Michael et al. (1992). “Separation of scattering and intrinsic attenuation for the Kanto-Tokai region, Japan, using measurements of S-wave energy versus hypocentral distance”. In: Geophysical Journal International 108.3, pp. 787–800. Hoshiba, Mitsuyuki (1991). “Simulation of multiple-scattered coda wave excitation based on the energy conservation law”. In: Physics of the Earth and Planetary Interiors 67.1-2, pp. 123–136. Hoshiba, Mitsuyuki (1997). “Seismic coda wave envelope in depth-dependent S wave velocity structure”. In: Physics of the Earth and Planetary Interiors 104.1-3, pp. 15–22. Kirkpatrick (1983). “Optimization by simulated annealing”. In: science 220.4598, pp. 671–680. Wu, R.S. and K. Aki (1985). “Multiple Scattering and Energy Transfer of Seismic Waves Separation of Scattering Effect from Intrinsic Attenuation II. Application of the Theory to Hindu Kush Region”. In: PAGEOPH 128.1/2, p. 198.