Dr. Aránguiz-Muñoz, Rafael

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.

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.

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.

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.

This study assesses physical infrastructure vulnerability for infrastructure network components exposed during the 2015 Illapel tsunami in Coquimbo, Chile. We analyse road and utility pole vulnerability to damage, based on interpolated and simulated tsunami hazard intensity (flow depth, flow velocity, hydrodynamic force and momentum flux) and network component characteristics. A Random Forest Model and Spearman’s Rank correlation test are applied to analyse variable importance and monotonic relationships, with respect to damage, between tsunami hazards and network component attributes. These models and tests reveal that flow depth correlates higher with damage, relative to flow velocity, hydrodynamic force and momentum flux. Scour (for roads and utility poles) and debris strikes (for utility poles) are strongly correlated with damage. A cumulative link model methodology is used to fit fragility curves. These fragility curves reveal that, in response to flow depth, Coquimbo roads have higher vulnerability than those analysed in previous tsunami event studies, while utility poles demonstrate lower vulnerability than with previous studies. Although we identify tsunami flow depth as the most important hydrodynamic hazard intensity metric, for causing road and utility pole damage, multiple characteristics correlate with damage and should also be considered when classifying infrastructure damage levels.

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.

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.

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.

The destructive potential of a massive tsunami is not only related to society’s response capacity and evacuation plans, but also to the urban morphology and land cover. The Boca Sur neigh- borhood is one of the areas in central Chile that is most exposed to tsunamis, and it is framed in the context of increasing urban growth. Faced with the worst tsunami scenario (earthquake Mw = 9.0), residents’ evacuation potential is analyzed by using a least-cost-distance model, and two scenarios of land cover change are considered (2002 and 2018). Presently, the sector’s urban areas have grown by 83%, therefore its population has also grown. The evacuation times consider an average walking speed (1.22 m/s) for both years (2002 and 2018). This analysis establishes that over 40% of the study area is more than 60 min away from the safe zones established by authorities. This differs greatly from the 22-min average tsunami arrival time. Moreover, 19% of the area could not be evacuated in less than 30 min. Therefore, it can be concluded that the increased urbanization in the coastal area has not improved travel times, as urban planning did not consider the optimization of evacuation times to the designated safe zones. In this study, we propose new safe zones that would help reducing evacuation times to 30 min. In addition to the area’s high tsunami risk, the evacuated population’s strong travel time limitations are added, prioritizing the incorporation of social and urban resilience elements that help to effectively reduce the risk of disaster, by using land-use planning and community work.

To unravel the relationship between earthquake and tsunami using ionospheric total electron content (TEC) changes, we analyzed two Chilean tsunamigenic subduction earthquakes: the 2014 Pisagua Mw 8.1 and the 2015 Illapel Mw 8.3. During the Pisagua earthquake, the TEC changes were detected at the GPS sites located to the north and south of the earthquake epicenter, whereas during the Illapel earthquake, we registered the changes only in the northward direction. Tide-gauge sites mimicked the propagation direction of tsunami waves similar to the TEC change pattern during both earthquakes. The TEC changes were represented by three signals. The initial weaker signal correlated well with Acoustic Rayleigh wave (AWRayleigh), while the following stronger perturbation was interpreted to be caused by Acoustic Gravity wave (AGWepi) and Internal Gravity wave (IGWtsuna) induced by earthquakes and subsequent tsunamis respectively. Inevitably, TEC changes can be utilized to evaluate earthquake occurrence and tsunami propagation within a framework of multi-parameter early warning systems.