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Quality of Seismic Sites:

PSD

The power spectral density curves (red curves) are referred to different one-hour records from a one-day helicorder. The new low-noise model (NLNM; green curve) and new high-noise model (NHNM; blue curve) levels (Peterson, 1993) are superimposed on the figure.

Peterson, J. (1993). Observation and modeling of seismic background noise, U.S. Geol. Surv. Open-File Rept. 93-322, 94 pp.



PSD Spectrograms:

PSD levels as a function of the period versus time in one-month-long spectrograms.



H/V Ratio

Horizontal to vertical (H/V) spectral ratios for each time windows (red curves). The blue curve represents the mean values of the H/V ratios, while the error bars in green represent the standard deviation.

Vassallo et. al, "Seismic Ambient Noise Analysis in Southern Italy", Bulletin of the Seismological Society of America, Vol. 102, No. 2, pp. 574-586, April 2012, doi: 10.1785/0120110018