Can Modeling the Geologic Record Contribute to Constraining the Tectonic Source of the 1755 CE Great Lisbon Earthquake?

Abstract

Many different sources have been proposed for the 1755 CE earthquake and tsunami, although to date no single source accounts for the massive energy-release required to: (1) explain the spatial pattern of earthquake intensity observed along the Cadiz Gulf and both the western and southern mainland Portuguese coast, and (2) agree with tsunami travel times observed around and over the Atlantic Ocean. Some studies suggest that this event was triggered by interconnected faults or landslide movements (e.g., Grácia et al., 2003;Vilanova & Fonseca, 2004). Furthermore, the Cadiz Accretionary Wedge (CAW), Horseshoe Fault (HSF), Gorringe Bank (GB), and Marquês de Pombal Fault (MPF) have all been proposed as primary locations where fault-rupture might have generated the 1755 CE earthquake (

Calibration, inversion and sensitivity analysis for hydro-morphodynamic models

“…Tsunami events are often difficult to simulate due to the large array of uncertain parameters, especially for historical scenarios where the only record is in the form of sediment deposits (e.g. Tang et al, 2018;Dourado et al, 2021). These uncertain parameters are often estimated by using educated guesses in a forward model and adjusting their value accordingly by comparing the model results with the data (see e.g.…”

“…These uncertain parameters are often estimated by using educated guesses in a forward model and adjusting their value accordingly by comparing the model results with the data (see e.g. Dourado et al, 2021). A more sophisticated approach is to use tsunami inversion models such as TSUNFLIND (see Tang and Weiss, 2015) which has been coupled with statistical methods in Tang et al (2018).…”

To what extent tsunami source information can be extracted from tsunami deposits? Implications from the 2011 Tohoku-oki tsunami deposits and sediment transport simulations

“…Tsunami deposits provide geological information on the inundation extents, flow conditions, and repeating run-up and backwash flows (Fujiwara 2008). They have widely been used for source modeling of paleotsunamis (Satake et al 2008;Namegaya and Satake 2014;Butler et al 2014;Ioki and Tanioka 2016;Sugawara et al 2019;Dourado et al 2021). Sandy tsunami deposits have been extensively studied because they can be easily identified as high-energy depositional events in stable environments, such as coastal lowlands (Minoura and Nakaya 1991).…”

“…Along with hydraulic data, information on deposit thickness and erosion depth can be obtained from tsunami sediment transport simulations and the results of the simulations can be compared directly with the sedimentary data of tsunami deposits. As the application of tsunami sediment transport simulations in tsunami deposit research is still at its nascent stage, examples of paleotsunami source modeling using sediment transport simulations are scarce (Sugawara et al 2019;Dourado et al 2021;Nakanishi and Ashi 2022). Thus, the validity and limitations of the application of tsunami sediment transport simulations in tsunami source modeling have not yet been explored.…”

“…Their deposit-based source modeling well reproduced the moment magnitude of the earthquake; however, the maximum slip was underestimated. Nevertheless, rectangular fault models are still dominantly used in source estimation of both modern and paleotsunamis (Satake et al 2013;Yamazaki et al 2018;Sugawara et al 2019;Dourado et al 2021;Nakanishi and Ashi 2022). Thus, an examination of the framework using the rectangular fault model can be useful to compare the results with those of the rectangular model reported in previous studies.…”