Ambient Seismic Noise Tomography of the Central Santiago Basin: Preliminary Results

Abstract eng:
Evaluation of the seismic site response of the Santiago Basin requires a detailed shear wave velocity model that accounts for vertical variations in relatively short distances. A temporal broadband station network was deployed in the center of the Basin and continuously recorded months of seismic ambient noise. The vertical components of the records were used to calculate empirical Green’s functions from noise cross-correlation. Frequency-domain cross-correlations were calculated based on Aki's (1957) formulation. Identification of zero-crossings in the real part of the cross spectrum, the cross-correlation function in the frequency domain, were associated with the Bessel function's zeros to obtain phase-velocity dispersion curves. Phase velocity maps for periods ranging from 1 to 3 s were constructed with phase dispersion curves using a regularized weighted least squares tomographic method. For this purpose, the study area was divided into a geographical grid with size 2x2 km. We concluded that the obtained velocity maps show that the south of the basin has larger velocities compared to the north zone, which is consistent with previous studies. The results are also consistent with the main geological boundaries of the basin (San Cristobal Hill, the Chena Hill, and the western flank of the Andes) and available large-scale velocity models.

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