Evidence of Surface Rupture Associated With Historical Earthquakes in the Lower Tagus Valley, Portugal. Implications for Seismic Hazard in the Greater Lisbon Area

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Canora Catalán, Carolina and Vilanova, Susana P. and De Pro Diáz, Yolanda and Pina, Pedro and Heleno, Sandra (2021) Evidence of Surface Rupture Associated With Historical Earthquakes in the Lower Tagus Valley, Portugal. Implications for Seismic Hazard in the Greater Lisbon Area. Frontiers in Earth Science . ISSN 2296-6463

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Official URL: https://doi.org/10.3389/feart.2021.620778




Abstract

The Lower Tagus Valley Fault, Portugal, has long been associated with the damaging earthquakes that affected the Greater Lisbon Area in historical times. These include a poorly documented earthquake that occurred in 1344, the relatively well-documented 1531 earthquake, and the most recent M6.0 1909 earthquake. In this work, we use a 0.5 m resolution LiDAR-based digital elevation model and a 0.5 cm resolution digital surface model based on UAV photogrammetry to accurately locate the fault scarps in the northernmost portion of the western fault strand and to select sites to perform paleoseimolological investigations. The paleoseismological and geochronological analysis performed in the Alviela trench site document the fault activity in the last 3000 years, including two earthquakes during historical times. We performed ground motion scenarios for 20 km, 40 km, and 60 km ruptures including the trench site. The ground motion fields obtained for the 40 km and 60 km ruptures are in agreement with most macroseismic intensity data available for the 1531 earthquake, implying a magnitude in the range M6.8–7.4. However, the degree of deformation preserved in the trench suggests a value closer to the lower magnitude bound. The intensity level observed in Lisbon in 1531 (IX) is lower than the modeled intensities for all considered scenarios and could be related to a particularly high level of vulnerability of the building stock.


Item Type:Article
Uncontrolled Keywords:lower Tagus valley fault zone, Lisbon 1531 earthquake, active faulting, paleoseismology trenching, ground motion scenarios, macroseismic intensity, digital elevation models
Subjects:Sciences > Geology > Geodynamics
Sciences > Geology > Seismology
ID Code:65457
Deposited On:12 May 2021 16:47
Last Modified:13 May 2021 07:49

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