Overview
This is a comparison of the noise levels between TA stations and selected stations from other
networks. The selected reference stations are the 39 EarthScope-supported US network sites,
4 GSN sites with STS-2 sensors (HRV,PFO,RSSD and SSPA) and 4 GSN sites with borehole sensors
(ANMO, DWPF, RSSD and SSPA). These stations were chosen based on similar instrumentation and
similar location (conterminuous United States) and represents only a first order comparison.
The noise level measurements ranged from January through October 2008. The median of the
Probability Distribution Function (PDF) of the Power Spectral Density is used to characterize
the most common level of background noise for each of these station sets.
The plots below illustrate that the TA stations operatate at noise levels similar to and sometimes
lower than stations with comparable instrumentation across the entire band between 0.1 and 172
second periods. The relatively high noise in the TA and US network stations at short periods
is interpreted as more sampling of cultural noise sources. The relatively lower noise levels
for TA stations between 0.9 and 4 second periods is potentially due to reduced sampling of
microseisms given the location of the array in 2008 (primarily the Rocky Mountains and cordillera).
The relative long-period noise levels for the TA stations are low compared to similar sites.
With the exception of short-period microseisms the GSN borehole stations are consistently the
lowest noise recordings as would be expected.
2008 (January-October) PDF median noise levels by network for vertical channels (new high/low noise models are in gray):
2008 (January-October) PDF median noise levels by network for horizontal channels, (new high/low noise models are in gray):
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