Dr. Aranguiz-Muñoz, Rafael

On September 28, 2018, a large earthquake and its accompanying tsunami waves caused severe damage to the coastal area of Palu Bay, in the central western part of Sulawesi Island, Indonesia. To clarify the distribution of tsunami inundation and run-up heights, and damage to coastal communities due to the tsunami, the authors conducted a field survey 1 month after the event. In the inner part of Palu Bay tsunami inundation and run-up heights of more than 4 m were measured at many locations, and severe damage by the tsunami to coastal low-lying settlements was observed. In the areas to the north of the bay and around its entrance the tsunami inundation and run-up heights were lower than in the inner part of the bay. The tsunami inundation distance depended on the topographical features of coastal areas. The southern shore of the bay experienced a longer inundation distance than other shores, though generally severe damage to houses was limited to within around 200 m from the shoreline. The main lessons that can be learnt from the present event are also discussed.

The variability in obtaining estimates of tsunami inundation and runup on a near‐real‐time tsunami hazard assessment setting is evaluated. To this end, 19 different source models of the Maule Earthquake were considered as if they represented the best available knowledge an early tsunami warning system could consider. Results show that large variability can be observed in both coseismic deformation and tsunami variables such as inundated area and maximum runup. This suggests that using single source model solutions might not be appropriate unless categorical thresholds are used. Nevertheless, the tsunami forecast obtained from aggregating all source models is in good agreement with observed quantities, suggesting that the development of seismic source inversion techniques in a Bayesian framework or generating stochastic finite fault models from a reference inversion solution could be a viable way of dealing with epistemic uncertainties in the framework of nearly‐real‐time tsunami hazard mapping.

On 1 April 2014, an earthquake with moment magnitudeMw8.2 occurred off the coast ofnorthern Chile, generating a tsunami that prompted evacuation along the Chilean coast. Here tsunamicharacteristics are analyzed through a combination of field data and numerical modeling. Despite theearthquake magnitude, the tsunami was moderate, with a relatively uniform distribution of runup, whichpeaked at 4.6 m. This is explained by a concentrated maximal slip at intermediate depth on the megathrust,resulting in a rapid decay of tsunami energy. The tsunami temporal evolution varied, with locations showingsustained tsunami energy, while others showed increased tsunami energy at different times after theearthquake. These are the result of the interaction of long period standing oscillations and trapped edgewave activity controlled by inner shelf slopes. Understanding these processes is relevant for the region,which still posses a significant tsunamigenic potential

Tsunami resonance and coupled oscillation of shelf and bays modes has been reported to beimportant in tsunami wave amplification. The main objective of this work is to study the spatial pattern ofnatural oscillation modes and to analyze the influence of several resonators on the coast of the centralChile, which has a complex morphology with several bays, submarine canyons, and a wide continentalshelf. First, natural oscillation modes were computed by means of modal analysis of local and regionaldomains. Second, a dense network of tide gauges and pressure sensors was analyzed to obtain backgroundspectra inside bays. Third, tsunami spectra were computed from both tsunami records and numericalsimulations. The results show that the use of modal analysis and background and tsunami spectra iseffective for identifying natural oscillation modes. In addition, a dense network of tide gauges is useful tovalidate the spatial pattern of these natural modes. It was observed that larger resonators and the shelf areimportant in coupling oscillation with local bays, such that large amplification can be observed. Finally,this analysis allowed the diverse effects of 2010 and 2011 tsunamis in the bays of central Chile to beexplained, making it possible to better address tsunami mitigation measures and the preparedness ofcoastal communities.

A GIS analysis on the urbanization spread (1725 to present) in the Greater Concepcion Region demonstrates that increasing the tsunami disaster resilience of coastal communities is a pressing issue in Chile, due to the continuous presence of human settlements in tsunami-prone areas. This research assesses the contribution of “hard-infrastructure” for increasing disaster resilience within five coastal towns (Dichato, Coliumo, Tumbes, Penco and Talcahuano). Structures were considered beneficial to resilience-building if they had multi-functional properties which aided in the social and/or economic recovery of the affected community. The assessment was carried out through in-depth interviews with local inhabitants until the point of data-saturation. Results reveal that all surveyed coastal towns had hard-infrastructure that was built after 2010, in the form of promenades and elevated housing. The former structures contributed positively to building economic resilience in Dichato, Talchuano and Penco, through the promotion of tourism and small-scale fishing activities. However, the physical design of the elevated houses was found to only facilitate recovery of community economic functions in Tumbes, while causing strain on the social fabric and possibly hindering tsunami evacuation in all other study sites. The mixed contribution of hard-infrastructure to coastal resilience highlights the need for the de-centralization of planning and reconstruction processes for a successful contextualization of the issue.