Three-dimensional paganica fault morphology obtained from hypocenter clustering (L'Aquila 2009 seismic sequence, Central Italy)

• Published in: Tectonophysics 2021-04, Vol.804 (C), p.228756, Article 228756
• Main Authors: Brunsvik, Brennan, Morra, Gabriele, Cambiotti, Gabriele, Chiaraluce, Lauro, Di Stefano, Raffaele, De Gori, Pasquale, Yuen, David A.
• Format: Article
• Language: English
• Subjects: Clustering; Earthquakes; Fault morphology; Geological faults; L'Aquila earthquake sequence; Microearthquakes; Modelling; Morphology; Rupture; Seismic activity; Sequencing; Splines; Three dimensional models
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2021.228756

In seismic modelling, fault planes are normally assumed to be flat due to the lack of data which can constrain fault morphology. However, incorporating 3D fault morphology is important for modelling several phenomena, for example calculating mainshock induced stress changes. We utilize a data-analytical method to unveil the 3D rupture morphology of faults using unsupervised clustering techniques applied to earthquake hypocenters in seismic sequences. We apply this method to the 2009 L'Aquila seismic sequence which involved a MW 6.1 mainshock on April 6th. We use a dataset of about 50,000 relocated events, mostly microearthquakes, reaching magnitude of completeness equal to 0.7. Clustering distinguishes the earthquakes as occurring in three main clusters along with other minor fault segments. We then represent the morphology of the main Paganica fault system (responsible for the largest mainshock) using splines. This method shows promise as a step toward robustly and quickly obtaining 3D rupture morphologies where earthquake sequences have been monitored. The 3D model is presented interactively online, and the processing is presented in an interactive Jupyter Notebook (https://bit.ly/2MnCFdj). •Machine learning can be used for retrieving the 3D morphology of faults quickly and objectively.•We apply clustering to L'Aquila sequence aftershock hypocenters to distinguish which faults they occurred on.•We use the clustered hypocenters to invert for the 3D morphology of the Paganica fault system.