Ambient Noise Levels in the Continental United States

We present a new approach to characterize the background seismic noise across the continental United States. Using this approach, power spectral den- sity (PSD) is estimated at broadband seismic stations for frequencies ranging from 0.01 to 16 Hz. We selected a large number of 1-hr waveform segments during a 3-yr period, from 2001 to 2003, from continuous data collected by the U.S. National Seismograph Network and the Advanced National Seismic System (ANSS). For each segment of continuous data, the PSD is estimated and smoothed in full- octave averages at 1/8 octave intervals. Powers for each 1/8 period interval were then accumulated in 1-dB power bins. A statistical analysis of power bins yields probability…