GNGTS 2021 - Atti del 39° Convegno Nazionale

GNGTS 2021 S essione 2.1 190 THE FAULT2SHA CENTRAL APENNINES DATABASE: A STRUCTURE FOR JOINING FAULT DATA PROVIDERS AND FAULT HAZARD MODELERS J. Faure Walker 1 , P. Boncio 2 , B. Pace 3 , G. Roberts 4 , L. Benedetti 5 , O. Scotti 6 , F. Visini 7 , L. Peruzza 8 1  Institute for Risk and Disaster Reduction University College London, London, UK  2  DiSPUTer Department, Università degli Studi G. d’Annunzio Chieti e Pescara, Chieti, Italy 3  InGEO Department, Università degli Studi G. d’Annunzio Chieti e Pescara, Chieti, Italy  4  Department of Earth and Planetary Sciences, Birkbeck College, London, UK  5  Aix-Marseille Université, CEREGE CNRS-IRD UMR 34, Aix en Provence, France 6 Bureau d’Evaluation des Risques Sismiques pour la Sûreté des Installations, IRSN, Fontenay-aux-Roses, Fran ce  7  Istituto Nazionale di Geofisica e Vulcanologia, Pisa, Italy 8  National Institute of Oceanography and Applied Geophysics - OGS, Borgo Grotta Gigante, Sgonico (Trieste), Italy  Including faults as seismogenic sources in probabilistic seismic hazard assessments (PSHA) has turned into a common practice as knowledge of active faults is improving. The most commonly used tools infer maximum magnitudes of earthquakes on individual faults from empirical relationships (e.g. Wells and Coppersmith, 1994) and use fault slip-rates to determine average earthquake recurrence rates (e.g., Pace et al., 2016). The Mw7.8 Kaikoura (New Zealand) earthquake (Hamling et al., 2017), however, highlighted that complex rupture scenarios occur including partial and multi-fault ruptures. Thus, fault-based hazard models are progressing to include more detail and complexity (e.g., Visini et al., 2020). Moreover, variable fault geometry has been shown to influence ground-shaking intensities (e.g., Faure Walker et al., 2019); slip-rates, has been identified as a key source of uncertainties in earthquake probability calculations (e.g., Field et al., 2014); and both coseismic and long-term, can vary significantly along the length of a fault (e.g., Sgambato et al., 2020). Efforts at improving in the provision of data are being made, however, current seismic source datasets (e.g. https://www. seismofaults.eu/; Styron et al., 2020) generally do not provide sufficient detail in mapped traces and slip-rate data, and do not give guidelines on how to aggregate mapped structures into a seismic source; this limits the interrogation of alternative rupture scenarios and the inclusion of detailed fault geometry and slip-rate profiles. As advances occur in our capability to create more detailed fault-based hazard models, depending on the availability of primary data and observations, it is desirable that such data can be organized in a way that is easily understood and incorporated into present and future models. To improve fault-based SHA, field geologists should provide the relevant observations, analysts should interpret field data appropriately, and the full range of uncertainties associated with the characterization of faults should be correctly understood and propagated in computation. We, the Fault2SHA Central Apennines Laboratory, have brought together representatives from research groups across multiple institutions comprising field geologists, seismic hazard modellers and practitioners to create a SHA-oriented database: the Fault2SHA Central Apennines Database (Faure Walker et al., 2020) . The database structure published in Faure Walker et al. (2021) and here presented aims to assist this process. We recommend stating what observations have led to different location and activity certainty and presenting slip-rate data with point location coordinates of where the data were collected with the time periods over which they were calculated. Such data reporting allows more complete uncertainty analyses in hazard and risk modelling, thus facilitating the exploration of the alternative main faults’ definitions in fault-based hazard and risk calculations and determination of the associated uncertainties. The structure of the database facilitates hazard uncertainty calculations in three ways. First, the Fault2SHA CAD provides four levels of fault activity and four levels of location certainty accompanied by the criteria that led to these designations, thus the levels and data that led to their assignment can be traced back to the observations made. Second, the database provides three levels of fault mapping: (1)