TSUNAMI SHELF RESONANCE ALONG THE NORTHERN CHILE COAST

Pablo Ignacio Cortes,P.A Catalã¡N

doi:10.9753/icce.v35.management.3

Abstract

This work presents the analysis of resonance in two of the main cities along the northern coast of Chile, where a large tsunamigenic potential remains despite recent earthquakes. By combining a modal analysis solving the theory of free and forced oscillations, with the analysis of background spectra derived from in situ measurements, the spatial and temporal structure of the modes are recovered. Comparison with spectra from three tsunamis of different characteristics shows that the modes found have been excited by past events. Moreover, a difference in the overall response between locations is found. Arica is more sensitive to the characteristics of the tsunami source, whereas Iquique shows a smaller dependency. Results are further contrasted with other methodologies with good agreement. These findings are relevant in characterizing the tsunami hazard in the area, and the methodology can be further extended to other areas along the Chilean coast.

Highlights

The controlling role of local bathymetry and topography over long waves and tsunamis near the coast has been suggested since early the 20th century
Resonant modes, both stationary and progressive, have been invoked to account for the late arrival of devastating tsunami waves observed at several Chilean coastal locations
Each tsunami spectrum has its own characteristics, there is a clear consistency between the results found using both background spectra and modal analysis

Summary

Introduction

The controlling role of local bathymetry and topography over long waves and tsunamis near the coast has been suggested since early the 20th century (see Rabinovich, 1997, for a review). The third wave was the most devastating in the port of Talcahuano during the tsunami generated by the Maule 2010 earthquake (Mw 8.8) (Yamazaki and Cheung, 2011) whereas a wave arriving 90 min after the main earthquake was the largest at Arica during the tsunami generated by the 2014 Pisagua earthquake (Mw 8.2) (Catalán et al, 2015) The ubiquity of these bathymetric control effects in areas prone to be affected by tsunami, makes the identification of the resulting resonant modes and their spatial characteristics to be of great significance to characterize and quantify tsunami hazard at coastal communities around the world, be it for hazard mitigation, preparedness or emergency response.

Objectives

Methods

Discussion

Conclusion