Exploring earthquakes through their audible sound: Listening to the sound of earthquake Doppler and anelastic attenuation phenomena

Περίληψη

The concept of addressing the sense of hearing for scientific reasons is not new, but has almost always been neglected in favor of methods using the sense of sight. This has happened for a variety of reasons, among them being the facts that quantitative calculations can be done and verified by viewing the data, thus leaving room for sight oriented analysis modes and technology to be developed and that the ear is an instrument used by most people to distinguish only qualitative auditory characteristics, often in an abstract way, therefore rendering it, initially, not usable for scientific research study. In the particular case of seismology, the approach is no different, although significant progress has been made roughly in the last fifteen years. The main phenomenon studied in this scientific field, the earthquake, has properties that can be analysed both sonically and optically and more importantly, both individually and combined. One can easily conceive the prevalence of the eye in recognizing static situations, such as the current stress distribution in an area depicted on a graph or the dominance of the ear in identifying time dependent changes, e.g. the attack and release times of any triggered sound (an earthquake?) listenable. Nevertheless, the lack of technological means designed directly for sonic earthquake research raises the question: How and to what extent is resorting to auditory methods useful for seismological study? Driven by these thoughts and by a more global interest in sound, an auditory investigation of earthquakes is attempted in this thesis. Various seismic records are audified and then processed with music production programs to extract results regarding two main subjects: i) The far-field Doppler effect in the Greek region caused by the 7/9/1999 M=5.9 Athens earthquake. ii) The anelastic attenuation phenomena in the Aegean Sea region studied for the intermediate depth 27/7/2006 M=3.3 Nisiros earthquake. The sound files are available in the enclosed CD.