How do automatic phase pickings based on deep neural networks perform on different-scale case studies?

Machine-learning algorithms are widely applied to facilitate human tasks. For instance, in seismology, they can help deliver high-resolution seismic catalogs including very small magnitude events that usually remain undetected by human analysts and by standard monitoring procedures. 

The new frontier of modern seismology is to exploit deep neural networks (DNN) to automatically detect P- and S-wave arrival times to obtain good-quality seismic event locations in terms of hypocentral errors. Increasing the number of events and seismic phases is essential to build complete earthquake catalogs to be used in seismological analyses (such as seismic hazard estimation, seismic tomography, fault zone structure determination, rupture mechanism study, etc.). 

Machine Learning methods are being integrated into large Research Infrastructures (RIs), like the European Plate Observing System (EPOS ERIC), which brings together 10 different scientific domains in Solid Earth Sciences. In this contribution, we present results from a specific Sponsored Research Activity promoted by the RI EPOS and dedicated to ML-driven methods for phase picking in seismic time series.

To ensure the correct recognition of seismic waves, neural networks trained on large and representative training datasets are essential. Here, we investigate the influence of the training dataset on the DNN PhaseNet performance, applying the method to three case studies. In the first case, the DNN trained with the Italian seismicity dataset (INSTANCE) is used to build a catalogue on the Fucino basin (Central Italy) study area; in the second case, we use the AQ2009 training dataset (based on the L’Aquila 2009 aftershocks) to analyse the 2016-2017 Amatrice-Visso-Norcia seismic sequence; and finally, the CREW training dataset (that contains P- and S-waves reflected on the mantle Earth and recorded at large epicentral distance) to detect P- and S- waves of teleseismic (regional) data acquired by the Adria Array project network. 

The use of different training datasets greatly improves the performance of the neural network in recognizing P and S phases, reducing the number of false positives and providing more accurate and precise P and S-phase arrival times.