Research Outputs

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Tsunami inundation limit based on probabilistic analysis of runup and inundation distance

2025, Ramos, Marilym, Dr. Aránguiz-Muñoz, Rafael, Dra. Bull-Torres, María

Tsunamis are devastating natural hazards that can reach runups of 30 m in coastal areas. One of the most important mitigation measures to save human lives is evacuation, which requires identification of both the inundation area and safe zones. Currently, a ground elevation of 30 m is used to determine safe zones in Chile. However, it has also been used for urban planning, for which the actual tsunami hazard may be overestimated. This research aims to propose a criterion based on probabilistic analysis to determine the tsunami inundation limit, considering both the runup and inundation distance from the shoreline. To this end, a synthetic database of runup and inundation distance from the shoreline was analyzed. First, stochastic earthquake sources were used to simulate tsunami events up to an inundation level in 10 coastal cities. Second, maximum runup and inundation distance were calculated for each tsunami scenario along transect lines perpendicular to the coastline. Finally, three exceedance probabilities of runup – 0.5%, 1%, and 2% in 50 years – were calculated to estimate the runup and inundation distances for each city. The results showed that geomorphology has an important role in runup and inundation distance. In addition, this research introduced new criteria for inundation limit identification, which are more flexible and accurate than the current 30-m ground elevation criterion used for tsunami risk assessment and urban planning. The application of this proposed method would allow local authorities to improve the locations of both critical infrastructure and safe zones.

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A new generation of tsunami inundation maps of Chilean cities: Tsunami source database and probabilistic hazard analysis

2024, Dr. Aránguiz-Muñoz, Rafael, Ramos, Marilym, Sepúlveda, Ignacio, Villagra, Paula

Tsunami inundation maps are crucial for understanding the impact of tsunamis and planning mitigation measures. Our research focuses on creating a database of stochastic tsunami scenarios along the Chilean subduction zone and probabilistic inundation maps for 11 coastal cities. We divided the Chile-Perú subduction zone into four seismic segments based on historical seismicity. Stochastic rupture scenarios, ranging from 8.0 to 9.6 magnitudes, were generated using the Karhunen-Loeve expansion. The Stochastic Reduced Order Model (SROM) helped select representative tsunami scenarios for each segment and magnitude bin. We then used the NEOWAVE model to simulate these scenarios to an inundation level, creating probabilistic tsunami maps for various return periods. Our findings reveal that local geography significantly influences tsunami inundation, with some areas facing high inundation risks while others experience minimal impacts. As a result, a uniform planning and design criterion across the entire country is not advisable; site-specific studies are necessary. These probabilistic scenarios can provide tailored solutions for different Chilean coastal cities, enhancing their resilience. Additionally, this research marks the first comprehensive probabilistic tsunami hazard analysis for the Chilean coast, considering multiple seismic sources, marking a crucial step toward full tsunami risk assessment for coastal communities.

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Analysis of the cascading rainfall-landslide-tsunami event of June 29th, 2022, Todos los Santos Lake, Chile

2023, Dr. Aránguiz-Muñoz, Rafael, Dr. Caamaño-Avendaño, Diego, Espinoz, Mauricio, Gómez, Matías, Maldonado, Felipe, Sepúlveda, Violchen, Rogel, Iván, Oyarzun, Juan Carlos, Duhart, Paul

A cascading rainfall–landslide–tsunami event occurred on June 29th, 2022, in Todos los Santos Lake, located in southern Chile, affecting the tourist town of Petrohué. The event took place after several days of heavy rain during an extratropical cyclone. Important data were collected during a field survey, including hillslope 3D scans, lake–river bathymetry, orthomosaic photos, and an assessment of damage to public infrastructure. The analysis showed that the landslide had an estimated length, width, and depth of 175 m, 40 m, and 1.5 m, respectively, which resulted in a total volume of 10,500 m3. The underwater runout distance of the landslide was estimated at 40 m, with a final water depth of 12 m. The initial tsunami wave was observed to be ~1 m, and since the distance from the landslide to the town was ~500 m, an arrival time of ~1 min was observed. Despite the small tsunami amplitudes, the pedestrian bridge of the floating pontoon collapsed due to the flow current and vertical oscillations. The results of the numerical simulation of the tsunami supported the observed data. They showed that the impact of the tsunami was only in the near field and was influenced by the bathymetry, such that refraction and edge waves were observed. The landslide occurred in an area where previous debris flows took place in 2013 and 2015. The main finding of the present research is that the occurrences of this and previous landslides were controlled by the presence of the Liquiñe–Ofqui fault zone, which generates broad areas of structural damage, with mechanical and chemical weathering significantly reducing rock strength. These observations provide a warning regarding the susceptibility of similar regions to other trigger events such as earthquakes and rainfall. This recent landslide highlights the need for a more comprehensive hazard assessment, for which probabilistic analysis could be focused on large active strike-slip fault systems. It also highlights the importance of community awareness, particularly in areas where tourism and real estate speculation have significantly increased urban development.

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Numerical analysis of seismic water level oscillations in canals

2020, Dr. Aránguiz-Muñoz, Rafael, Ohira, Koichiro, Takabatake, Tomoyuki, Esteban, Miguel, Mall, Martin, Shibayama, Tomoya

Water level oscillations induced by the ground motion of an earthquake have occasionally been observed in a closed or partially enclosed water system. The generated water disturbances can induce localized flooding, boat collisions, breakage/damage of moored cables due to water disturbances, or even the capsizing of vessels. In this study, the authors focused on cases of seismic water level oscillations in canals and attempted to investigate the potential hazards of and effective countermeasures against them through numerical simulations. The proposed numerical simulation model was first validated by reproducing the water level oscillation that was actually observed at a canal in Mexico City (Xochimilco Canal) during the 2017 Central Mexico Earthquake. The method was then applied to one of the canals in Tokyo (Keihin Canal) to clarify the potential water level fluctuations that can take place due to this phenomenon. The results indicate that while the risks of local inundation would be low, small boats, which can be found in many places in the canal, are at risk of capsizing. Finally, the use of wave-dissipating blocks was found to be an effective countermeasure to decrease the potential for a significant seismic water level oscillation to take place in this canal.

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Reconstruction and numerical modeling of historical and paleo-tsunamigenic landslides in Lake Rupanco, Chile

2025, Quiroga, Juan Pablo, Dr. Aránguiz-Muñoz, Rafael, Hernández-Madrigal, Víctor Manuel, Dr. Muñoz-Ortiz, Enrique

Landslide-induced tsunamis pose a significant yet underrecognized hazard in lake-rich, tectonically active regions such as south-central Chile. This study reconstructs and numerically models two contrasting tsunamigenic landslide scenarios in Lake Rupanco: (i) a multi-source subaerial landslide triggered by the 1960 Valdivia earthquake (Mw 9.5), and (ii) a large, deep-seated paleo-landslide inferred from geomorphological and bathymetric evidence. Field surveys, historical imagery, and a high-resolution topo-bathymetric dataset were used to define landslide geometries and initial conditions. Simulations were performed using the Landslide-HySEA model, calibrated through a global sensitivity analysis to constrain key rheological parameters. The 1960 scenario generated peak wave amplitudes of up to 33.3 m, while the paleo-landslide produced waves reaching 22.0 m. Both events resulted in run-up heights exceeding 10 m and inundation distances over 200 m along the lake’s eastern and southern shores. The results demonstrate that landslide dynamics—not just volume—are critical in tsunami generation, and highlight the importance of integrating both historical and paleo-events into hazard assessments for confined water bodies in seismically active settings.

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A nature-based exploration of resilience capacity in coastal settlements exposed to tsunamis along the southern Pacific coast

2024, Villagra, Paula, Peña y Lillo, Oneska, Herrmann-Lunecke, Marie Geraldine, Dr. Aránguiz-Muñoz, Rafael, Baez, Andrea

The speculation of coastal land for tourism and housing has led to the rapid urbanization of Chilean coastal settlements and to the reduction of critical ecosystems that contribute to resilience against tsunami hazards. This study analyzes the mitigative and adaptive capacities of these settlements based on their natural resources, focusing on differences across settlements with varying degrees of urbanization. Mitigative capacity refers to the ability to minimize the impact of a tsunami through bioshields like coastal forests, wetlands, and dunes in the Coastal Plane. Adaptive capacity encompasses longer-term resources that support recovery, such as food, water, and refuge provided by forests, prairies and agricultural land among others in the Coastal Range. Using spatial and multivariate analyses, 53 coastal settlements were evaluated, leading to three settlement clusters with distinct degree of urbanization, type of settlement (village or city), and differences in their latitudinal distribution and in the number of prairies and agricultural land in the Coastal Range. Results show no significant differences between settlement clusters and mitigative capacity. On the other hand, the study finds that cities' type of settlements, with greater prairie and agricultural land in the Coastal Range, particularly in central and northern Chile, show a higher capacity for adaptation, based on transportation and refuge available after the tsunami. This research highlights the crucial role of natural resources in both immediate disaster mitigation and long-term adaptation. Understanding the differences in resource availability among settlements can inform urban planning strategies to develop tsunami-resilient communities along Chile's southern Pacific coast.

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The AD1835 eruption at Robinson Crusoe Island discredited: Geological and historical evidence

2021, Dr. Aránguiz-Muñoz, Rafael, Lara, Luis, Moreno, Rodrigo, Valdivia, Valentina, Lagos, Marcelo

A submarine eruption in Cumberland Bay, Robinson Crusoe Island, was reported by Thomas Sutcliffe, the former British Governor, shortly after the earthquake that struck the coast of Chile on 20 February 1835. This episode was described by Charles Darwin in his Voyage of the Beagle and extensive mention has been made since then, especially stimulated by a renowned painting by J.M. Rugendas. Because of the apparent causal relation, this event has also been widely cited as an example of remote tectonically triggered eruption. However, there are inconsistencies that pose doubts about the actual occurrence of an eruption. Here we present evidence against the hypothetical eruption based on both the absence of any geological evidence and a reinterpretation of the historical accounts. We first observe that no bathymetric anomaly is present immediately below the place of the depicted ‘eruptive column’. We also note the absence of any deposit or recent volcano morphology and then unravel some incompatibility between the expected volcanological parameters and the featured column. In addition, we analyse the historical records and conclude that they are compatible with a tsunami entering the bay. By means of numerical simulations we further demonstrate that the accounts well match with the expected behaviour of a distant earthquake-triggered tsunami. We infer that some tsunami-related processes (sound waves, rockfalls, lightning) may have been misunderstood at that time. The latter corresponds to the current knowledge of natural processes but also could have been deliberatively amplified in Sutcliffe’s report. Our multidisciplinary approach provides full consistent geographical evidence of a fact that did not happen. This finding is relevant from the hazard’s perspective, but also for the science of earthquakes and eruptions, or the knowledge of processes that control the late secondary volcanism at oceanic islands and seamounts.

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Modeling of solitary wave-induced scour around structures: SPH-based analysis and experimental validation

2025, Fuentes, Benjamín, Cruchaga, Marcela, Dr. Aránguiz-Muñoz, Rafael, Dinamarca, Javiera

This paper investigates solitary wave-induced scour around square structures, a critical factor affecting the integrity of coastal infrastructure. The phenomenon is studied numerically and validated through original experiments conducted in our laboratories. Specifically, a solitary wave interacting with a square structure on a beach with bathymetry representative of Chilean coasts is analyzed. Additional validation is performed using an experiment from the literature involving dam-break-induced scour behind coastal dikes. The numerical modeling is carried out using DualSPHysics, an open-source simulation tool based on the Smoothed Particle Hydrodynamics (SPH) method, which has shown effective results for wave modeling and scour studies. This study demonstrates the model’s effectiveness in addressing wave-induced scour problems. The interaction between a tsunami-representative solitary wave and the sediment is modeled using the Herschel-Bulkley-Papanastasiou (HBP) model for granular materials. The results show that the numerical model, combined with the rheological model, accurately predicts the maximum scour depths in both configurations. Furthermore, the simulations closely align with experimental observations and previous studies, confirming that scour depth correlates with flow depth, with deeper scour occurring at the corners of structures compared to the central faces. These findings improve predictive capabilities for tsunami impacts on coastal structures, highlighting the need for future research to incorporate more realistic wave characteristics to enhance prediction accuracy.

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Analysis of climate change and climate variability impacts on coastal storms induced by extratropical cyclones: a case study of the August 2015 storm in central Chile

2024, Gómez, Matías, Dr. Aránguiz-Muñoz, Rafael, Mäll, Martin

The projected increase in coastal risk requires a reevaluation of coastal risk reduction strategies. A multi-model approach is proposed to examine the variability of coastal storms influenced by climate change and El Niño Southern Oscillation (ENSO). To this end, the historic coastal storm of August 8 2015, resulting from a local extratropical cyclone (ETC) off the central Chilean coast, was analyzed through the coupling of the WRF atmospheric model, Delft3D FM (D-FLOW and D-WAVE modules), and EOT20 astronomical tide model. The results show that the characteristics of local ETCs are susceptible to regional temperature gradients associated with climate change and ENSO. The coastal storm of August 8 2015, presented a decrease in wave height and counterclockwise rotation of wave direction along the Chilean coast under the climate change scenario. Meanwhile, the ENSO scenarios under cold conditions generated a ETC track’s displacement toward the north, causing both an increase in wave height along the coast of the Antofagasta and Atacama regions and a decrease in wave height in the Valparaíso, O’Higgins, and Maule regions. Findings from this study emphasize the importance of considering dynamic design for coastal structures rather than traditional methods to adapt to changing storm patterns.

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Tsunami awareness and evacuation behaviour during the 2018 Sulawesi earthquake tsunami

2020, Shafiyya Harnantyari, Anisa, Takabatake, Tomoyuki, Esteban, Miguel, Valenzuela, Paolo, Nishida, Yuta, Shibayama, Tomoya, Achiari, Hendra, Rusli, Marzuki, Abdul Gafur, Marzuki, Muhammad Fadel Hidayat, Dr. Aránguiz-Muñoz, Rafael, Kyaw, Thit Oo

On September 28, 2018 significant tsunami waves, which are considered to have been generated by submarine landslides, struck the shorelines of Central Sulawesi, Indonesia. One month after the event, the authors conducted a questionnaire survey of the affected areas (Donggala Regency and Palu City) to collect information on the evacuation behaviour and tsunami awareness of local residents. In the present study, in addition to summarising the overall trend of the survey results using descriptive statistics, a chi-squared test was applied to analyse the significance of the relationship between tsunami awareness and evacuation behaviour and the demographic characteristics of respondents. The analysis of the results demonstrates that although the respondents generally have a high level of tsunami awareness, younger people and Donggala Regency residents have an overall lower understanding of the phenomenon. It was also found that 82.5% of the population evacuated after witnessing others evacuating during the event. As there was no official warning to residents before the arrival of the tsunami, this social trigger played a significant role in prompting evacuation and decreasing the number of casualties. The present study also revealed that many people faced congestion while evacuating (especially in Palu City). This highlights the need to introduce additional tsunami disaster mitigation strategies to ensure that all residents can swiftly evacuate during such incidents.