Which Fault Threatens Me Most? Bridging the Gap Between Geologic Data-Providers and Seismic Risk Practitioners

Abstract

The aim of the Fault2SHA European Seismological Commission Working Group Central Apennines laboratory is to enhance the use of geological data in fault-based seismic hazard and risk assessment and to promote synergies between data providers (earthquake geologists), end-users and decision-makers. Here we use the Fault2SHA Central Apennines Database where geologic data are provided in the form of characterized fault traces, grouped into faults and main faults, with individual slip rate estimates. The proposed methodology first derives slip rate profiles for each main fault. Main faults are then divided into distinct sections of length comparable to the seismogenic depth to allow consideration of variable slip rates and the exploration of multi-fault ruptures in the computations. The methodology further allows exploration of epistemic uncertainties documented in the database (e.g., main fault definition, slip rates) as well as additional parameters required to characterize the seismogenic potential of fault sources (e.g., 3D fault geometries). To illustrate the power of the methodology, in this paper we consider only one branch of the uncertainties affecting each step of the computation procedure. The resulting hazard and typological risk maps allow both data providers and end-users 1) to visualize the faults that threaten specific localities the most, 2) to appreciate the density of observations used for the computation of slip rate profiles, and 3) interrogate the degree of confidence on the fault parameters documented in the database (activity and location certainty). Finally, closing the loop, the methodology highlights priorities for future geological investigations in terms of where improvements in the density of data within the database would lead to the greatest decreases in epistemic uncertainties in the hazard and risk calculations. Key to this new generation of fault-based seismic hazard and risk methodology are the user-friendly open source codes provided with this publication, documenting, step-by-step, the link between the geological database and the relative contribution of each section to seismic hazard and risk at specific localities.

Earthquake Rupture Forecasts for the MPS19 Seismic Hazard Model of Italy

“…For some faults, for example, slip rates may bear the effects of sediment compaction [e.g., Scrocca et al, 2007;Maesano et al, 2015], gravitational movements [Kastelic et al, 2017;Di Naccio et al, 2019], or aseismic behaviour . Moreover, fault-based ERFs could potentially benefit from the recent development of multi-fault rupture modeling [Field et al, 2013;Chartier et al, 2019;Verdecchia et al, 2018;Visini et al, 2020;Valentini et al, 2020;Scotti et al, 2021]. Although certainly more mature than the others, areabased ERFs can also benefit from other improvements; the choice of criteria for drawing the areas, and in particular, the balance between expert judgment and data-driven approaches can still be further explored.…”

Integrating Long and Short‐Term Time Dependencies in Simulation‐Based Seismic Hazard Assessments

“…(2019) are used where relevant information is missing from Scotti et al. (2021). Consistent with Valentini et al.…”

“…(2019), the magnitude scaling relationship by Leonard (2010) is used in this study. The calibration of the fault‐based seismicity module also includes paleoseismic/historical records, which are available for four locations along the FucinoOvindoliPezza fault (Galli et al., 2008, 2012; Pantosti et al., 1996; Scotti et al., 2021), two locations along the CampoFelice fault (Salvi et al., 2003; Scotti et al., 2021), three locations along the MtVettore fault (Cinti et al., 2019; Scotti et al., 2021), one location along the PaganicaSanDemetrioNeVestini fault (Valentini et al., 2019), and one location along the Sulmona fault (Galli et al., 2014).…”

The Segmented Campo Felice Normal Faults: Seismic Potential Appraisal by Application of Empirical Relationships Between Rupture Length and Earthquake Magnitude in the Central Apennines, Italy

“…In assessing the seismic potential of fault systems, adjacent fault segments should be considered collectively to test the possibility of their coseismic simultaneous activation (Wesnousky, 2008;Xu et al, 2018;Brozzetti et al, 2019;Iezzi et al, 2019;Morell et al, 2020;Sgambato et al, 2020;Scotti et al, 2021;Walker et al, 2021). The capability of coseismicallybreaking inter-segment barriers depends on the degree of mechanical interaction: obviously, the higher the linkage between fault segments, the more prone they are to break in cascading coseismic events (Manighetti et al, 2007).…”

“…In assessing the seismic potential of fault systems, adjacent fault segments should be considered collectively to test the possibility of their coseismic simultaneous activation (Brozzetti et al., 2019; Iezzi et al., 2019; Morell et al., 2020; Scotti et al., 2021; Sgambato et al., 2020; Walker et al., 2021; Wesnousky, 2008; Xu et al., 2018). The capability of coseismically breaking inter‐segment barriers depends on the degree of mechanical interaction.…”