Insights into earthquake ruptures from analysis of DAS data

The possibility to exploit fibre optic cables through DistributedAcoustic Sensing (DAS) systems is a powerful tool for seismologists, providing spa-tially continuous recordings of earthquakes. This technology is suitable for the anal-ysis of seismic ruptures, continuously mapping the source properties as observedalong the sensed cable. In this study we describe how far-field strain radiation froma circular rupture can be modelled to evaluate the earthquake size and released stressdrop during fault slippage. We then fit earthquake signals recorded along a 150 kmlong dark fibre cable deployed offshore the coast of Central Chile sensed by DAS, toevaluate the rupture properties of small to moderate subduction events. We showthat stress drop increases for moderate magnitude events, indicating a complexityin the slip pattern and the presence of small scale asperities also at this scale