  We present a method to characterize the noise in ground-based
gravitational-wave observatories such as the Laser Gravitational-Wave
Observatory (LIGO). This method uses linear regression algorithms such as the
least absolute shrinkage and selection operator (LASSO) to identify noise
sources and analyzes the detector output versus noise witness sensors to
quantify the coupling of such noise. Our method can be implemented with
currently available resources at LIGO, which avoids extra coding or direct
experimentation at the LIGO sites. We present two examples to validate and
estimate the coupling of elevated ground motion at frequencies below 10 Hz with
noise in the detector output.
