ALBERT

Description: In recent years, it has become clear that Distributed Acoustic Sensing (DAS) is capable of capturing many seismic signals, including earthquakes across a range of magnitudes. Given the vast networks of fibre optic cables beneath urban areas, there is great potential for the utilisation of existing telecommunication fibres for the purpose of seismic monitoring and hazard analysis. However, it is crucial that we first understand the capabilities and potential limitations of applying DAS in this way.In late 2021, we collected over one month of urban DAS data beneath North-East Athens, Greece, using ~ 24 km of telecommunication fibre owned by the OTE group. This urban dataset contains a broad range of signals, including local anthropogenic activities, as well as numerous seismic events.We build a catalogue of events observed within the DAS data, and assess differences between our DAS event catalogue and that of the regional seismic network managed by the National Observatory of Athens (NOA). This includes an analysis of to what extent sensitivity to events is influenced by event magnitude, depth, distance and azimuth. The dense spatial sampling offered by DAS facilitates the use of novel array processing methods, which can be used to detect smaller events. We determine whether the benefits of using DAS and applying such methods within a regional seismic network justify the additional costs.We also explore the influence of the exact fibre deployment and local geological conditions on the seismic events recorded, and how this information can be considered for future DAS earthquake-monitoring experiments.