Sensitivity of Tsunami Scenarios to Complex Fault Geometry and Heterogeneous Slip Distribution: Case-Studies for SW Iberia and NW Morocco

Open Access

Abstract

19 pages, 9 figures, 1 table, supporting information https://doi. org/10.1029/2021JB022127.-- Data Availability Statement: Fault meshes and Slip distributions are available at the figshare repository: https://figshare.com/s/02e19886d2ded8ec9145. MCS data is available at the following published articles: SWIM profiles: Bartolome et al., (2012); Martínez-Loriente (2013); Martínez-Loriente et al., (2013); Martínez-Loriente et al., (2018). VOLTAIRE profiles: Banda et al., (1995); Zitellini et al., (2001); Terrinha et al., (2009). BIGSETS profiles: Zitellini et al., (2001); Zitellini et al., (2004); Vizcaino (2009); Serra et al., (2020). IAM profiles: Sartori et al., (1994); Jiménez-Munt et al., (2010); Terrinha et al., (2009); Zitellini et al., (2009). ARRIFANO profiles: Sartori et al., (1994); Zitellini et al., (2004); Serra et al., (2020). Bathymetry used for the tsunami simulations (Figures 3-7) is available in the SRTM public repository: https://www2.jpl.nasa.gov/srtm/. Detailed bathymetry used to define the fault traces is published in Zitellini et al., 2009. Seismicity data used in Figure 1a is available at the IGN catalog website: https://www.ign.es/web/ign/portal/sis-catalogo-terremotos ; The SW Iberian margin is one of the most seismogenic and tsunamigenic areas in W-Europe, where large historical and instrumental destructive events occurred. To evaluate the sensitivity of the tsunami impact on the coast of SW Iberia and NW Morocco to the fault geometry and slip distribution for local earthquakes, we carried out a set of tsunami simulations considering some of the main known active crustal faults in the region: the Gorringe Bank (GBF), Marquês de Pombal (MPF), Horseshoe (HF), North Coral Patch (NCPF) and South Coral Patch (SCPF) thrust faults, and the Lineament South strike-slip fault. We started by considering for all of them relatively simple planar faults featuring with uniform slip distribution; we then used a more complex 3D fault geometry for the faults constrained with a large 2D multichannel seismic dataset (MPF, HF, NCPF, and SCPF); and finally, we used various heterogeneous slip distributions for the HF. Our results show that using more complex 3D fault geometries and slip distributions, the peak wave height at the coastline can double compared to simpler tsunami source scenarios from planar fault geometries. Existing tsunami hazard models in the region use homogeneous slip distributions on planar faults as initial conditions for tsunami simulations and therefore underestimate tsunami hazard. Complex 3D fault geometries and non-uniform slip distribution should be considered in future tsunami hazard updates. The tsunami simulations also support the finding that submarine canyons attenuate the wave height reaching the coastline, while submarine ridges and shallow shelves have the opposite effect ; The authors are grateful for funding from MINECO through the project INSIGHT (CTM2015-70155-R), the project STRENGTH (PID2019-104668RB-I00), a MINECO FPI-2016 grant (BES-2016-078877) to Cristina S. Serra (ICM-CSIC), a MICINN "Juan de la Cierva-2017" grant (IJCI-2017-33838) to Sara Martinez-Loriente (ICM-CSIC), and from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2019-000928-S). We acknowledge the resources made available by the SISMOLAB-3D at INGV for the 3D fault modeling ; Peer reviewed