Browsing by Author "Vilanova, Susana P."
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- Incorporating descriptive metadata into seismic source zone models for seismic-hazard assessment : a case study of the Azores-West Iberian RegionPublication . Vilanova, Susana P.; Nemser, Eliza S.; Besana-Ostman, Glenda M.; Bezzeghoud, Mourad; Borges, José Fernando; Silveira, António Brum da; Cabral, João; Carvalho, João; Cunha, Pedro Proença e; Dias, Ruben Pereira; Madeira, José; Lopes, Fernando Carlos; Oliveira, Carlos Sousa; Perea, Hector; García-Mayordomo, Julián; Wong, Ivan G.; Arvidsson, Ronald; Fonseca, João F. B. D.In probabilistic seismic-hazard analysis (PSHA), seismic source zone (SSZ) models are widely used to account for the contribution to the hazard from earthquakes not directly correlated with geological structures. Notwithstanding the impact of SSZ models in PSHA, the theoretical framework underlying SSZ models and the criteria used to delineate the SSZs are seldom explicitly stated and suitably documented. In this paper, we propose a methodological framework to develop and document SSZ models, which includes (1) an assessment of the appropriate scale and degree of stationarity, (2) an assessment of seismicity catalog completeness-related issues, and (3) an evaluation and credibility ranking of physical criteria used to delineate the boundaries of the SSZs. We also emphasize the need for SSZ models to be supported by a comprehensive set of metadata documenting both the unique characteristics of each SSZ and the criteria used to delineate its boundaries. This procedure ensures that the uncertainties in the model can be properly addressed in the PSHA and that the model can be easily updated whenever new data are available. The proposed methodology is illustrated using the SSZ model developed for the Azores–West Iberian region in the context of the Seismic Hazard Harmonization in Europe project (project SHARE) and some of the most relevant SSZs are discussed in detail.
- The Eastern Lower Tagus Valley Fault Zone in central Portugal : active faulting in a low-deformation region within a major river environmentPublication . Canora, Carolina; Vilanova, Susana P.; Besana-Ostman, Glenda M.; Carvalho, João; Heleno, Sandra; Fonseca, João F. B. D.Active faulting in the Lower Tagus Valley, Central Portugal, poses a significant seismic hazard that is not well understood. Although the area has been affected by damaging earthquakes during historical times, only recently has definitive evidence of Quaternary surface faulting been found along the western side of the Tagus River. The location, geometry and kinematics of active faults along the eastern side of the Tagus valley have not been previously studied. We present the first results of mapping and paleoseismic analysis of the eastern strand of the Lower Tagus Valley Fault Zone (LTVFZ). Geomorphological, paleoseismological, and seismic reflection studies indicate that the Eastern LTVFZ is a left-lateral strike-slip fault. The detailed mapping of geomorphic features and studies in two paleoseismic trenches show that surface fault rupture has occurred at least six times during the past 10 ka. The river offsets indicate a minimum slip rate on the order of 0.14–0.24 mm/yr for the fault zone. Fault trace mapping, geomorphic analysis, and paleoseismic studies suggest a maximum magnitude for the Eastern LTVFZ of Mw ~ 7.3 with a recurrence interval for surface ruptures ~ 1.7 ka. At least two events occurred after 1175 ± 95 cal yr BP. Single-event displacements are unlikely to be resolved in the paleoseismic trenches, thus our observations most probably represent the minimum number of events identified in the trenches.