| | Abstract
This article presents
the main characteristics of the broadband (BB) seismic station of
Túnel del Cadí (CAD) along with an analysis of seismic
noise and its correlation with regional meteorological conditions. The
quality of the sensor site (in a closed cave, 80 m below surface)
provides ideal conditions for the location of a BB station with the
ability to detect small events. Through the analysis of noise series 30
min in length during a period of 15 months, a characterization of the
level of detectability has been performed. Using one estimate of noise
per day, the seasonal variation of the amplitude of the noise has been
analyzed, and using four samples per day, short-period variations have
been studied and compared with external meteorological conditions.
Results show that the characteristics of the station are similar to a
typical station placed in a hard basement rock and that there are no
differences between the behavior of the three components. The analysis
of several spectral components shows the relative excitation of
microseisms and atmospheric disturbances that may differ more than one
order of magnitude. There is a clear anticorrelation between the noise
amplitude spectra and the atmospheric pressure in short-period
variations, and the high-frequency noise is directly related to the
external wind velocity, although there is not a direct impact to the
sensor site. No correlation of the shape of the spectra (general or for
specific frequencies) with any meteorological parameter is
observed.
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