Fig. 1

Characteristic spectral features of seismic noise from 0.0001 to 10 Hz. This is a model (NLNM) by Peterson (1993). For frequencies below 0.003 Hz, atmospheric processes are the main source of seismic noise but oceanic processes are the main source in the frequency band from 0.003 to 1.0 Hz; there are three main seismic noises in this frequency band and they are, from low frequency, the hum, the primary microseism and the secondary microseism