Seismic Background Noise Analysis

We acquired SEED data volumes containing a network day (2005.268) of 1 Hz three-component broadband data from the TA transportable network (27 stations) and from the BK permanent network (26 stations). This data was used to characterize the seismic background noise in the 30-60 second LP band. We also acquired SEED data volumes containing two network hours (2005.268.0000-0200) of 40 Hz three-component broadband data from the TA transportable network and from the BK permanent network (day 2005.268.0000-0200). This data was used to characterize the seismic background noise in the 1-5 Hz SP band.

The observed vertical-component LP (30-60 second period) seismic background noise PSD is shown in Figure 10.5 and the corrsponding horizontal-component noise is shown in Figure 10.6. The spread between the quietest and noisiest stations on the vertical-component is $\sim $20 dB with only four stations in the two noisiest levels. The spread between the quietest and noisiest stations on the horizontal-component is $\sim $30 dB with 19 stations (36%) in the two noisiest levels. The stations with the low observed seismic noise levels are generally sites on bed rock or in hard rock mines and remote from cultural noise sources. The stations with high horizontal-component PSD noise levels are generally sites with either thick alluvial deposits or high ambient cultural noise levels.

Figure 10.5: Results of seismic background noise PSD analysis of the vertical-component LP (30-60 second) oberved at BK and TA network stations in Northern and Central California.
\begin{figure}\begin{center}
\epsfig{file=bob05_3_1.eps, width=7.5cm}\end{center}\end{figure}

Figure 10.6: Results of seismic background noise PSD analysis of the horizontal-component LP (30-60 second) oberved at BK and TA network stations in Northern and Central California.
\begin{figure}\begin{center}
\epsfig{file=bob05_3_2.eps, width=7.5cm}\end{center}\end{figure}

Figure 10.7: Results of seismic background noise PSD analysis of the vertical-component SP (1-5 Hz) oberved at BK and TA network stations in Northern and Central California.
\begin{figure}\begin{center}
\epsfig{file=bob05_3_3.eps, width=7.5cm}\end{center}\end{figure}

Figure 10.8: Results of seismic background noise PSD analysis of the horizontal-component SP (1-5 Hz) oberved at BK and TA network stations in Northern and Central California.
\begin{figure}\begin{center}
\epsfig{file=bob05_3_4.eps, width=7.5cm}\end{center}\end{figure}

The observed vertical-component SP (1-5 Hz) seismic background noise PSD is shown in Figure 10.7 and the corrsponding horizontal-component noise is shown in Figure 10.8. The spread between the quietest and noisiest stations on the vertical-component is $\sim $50 dB with nine stations in the two noisiest levels. The spread between the quietest and noisiest stations on the horizontal-component is likewise $\sim $50 dB with 10 stations in the two noisiest levels. The stations with high horizontal-component PSD noise levels are generally either sites with thick alluvial deposits or high ambient cultural noise levels.

Berkeley Seismological Laboratory
215 McCone Hall, UC Berkeley, Berkeley, CA 94720-4760
Questions or comments? Send e-mail: www@seismo.berkeley.edu
© 2005, The Regents of the University of California