On the origin of the signals observed across the seismic spectrum

Abstract

The increasing number of broad-band seismic stations recording the full spectrum of the seismic wavefield continuously has boosted interest in background signals recorded in the absence of earthquakes. Different human-made and natural phenomena other than earthquakes result in Earth vibrations that are recorded on seismometers. Those signals have classically been considered as disturbing noise, but in the last decades this view has turned, as it has been shown that seismic data can be used not only to monitor earthquake activity, but also to investigate climatic changes, track hurricanes, monitor river flows, or survey anthropogenic activity, hence making new links between seismology and different research fields. This contribution reviews state-of-the-art knowledge on the sources of seismic energy in different frequency bands using a single, two-weeks-long, seismic data file recorded by a high quality broad-band station located in the Pyrenees. This data allows exploration of the wide spectrum of ground motion, enabling a review of different processes involved in the generation of what seismologists commonly regard as background noise when focusing on ground motion from local and teleseismic earthquakes and explosions recorded in the same time interval.