Assessing the Use of Tsunami Simulations as a Tool to Predict Source Magnitudes and Locations of Paleoearthquakes in Chile

Author

Rebeca Isabel Becerra, Central Washington UniversityFollow

Document Type

Thesis

Date of Degree Completion

Spring 2018

Degree Name

Master of Science (MS)

Department

Geological Sciences

Committee Chair

Breanyn MacInnes

Second Committee Member

Lisa Ely

Third Committee Member

Walter Szeliga

Abstract

A long-term goal of paleotsunami studies is the ability to predict paleoearthquake parameters based on tsunami deposits found on land. Chile provides an exemplary location for testing methods of making these predictions because the historical record includes 41 major earthquakes as far back as 1562 AD, and there are many known paleotsunami deposits throughout the region. Using these records as a comparison tool, I evaluated simulated tsunami wave heights and inundation extent with the tsunami model GeoClaw for nine hypothetical tsunamigenic large earthquakes (M_w 8.6, 8.8, and 9.0) in south-central Chile with epicenters at -35.1º, -38.8º, and -42.9º. As expected, increasing earthquake magnitude produced larger tsunami wave heights, more sites with tsunami inundation, greater inundation extent, larger seafloor deformation, and generally earlier arrival times. Simulations showed tsunamis from M_w 9.0 earthquakes can inundate coastal plains from nearfield sources, but not exclusively as M_w 8.6 and M_w 8.8 scenarios can produce wave heights over 5 m at some sites. To infer earthquake properties, I analyzed sites to determine where differences between wave heights from variable earthquake magnitudes and source locations were magnified, defined as promising sites. At these promising sites, 60% of them showed tsunami wave heights averaging ≥0.5 m between simulations, which is a substantial number of sites in the 1,000-km stretch of coast off south-central Chile. The number of sites sensitive to magnitude and/or source location amounted to more than half of the total, proving tangibility considering the quality of bathymetry available. These nine earthquakes showed that more extensive comparisons of possible paleoearthquake parameters with on-land observations is a promising approach to defining characteristics of historical and prehistoric events.

Recommended Citation

Becerra, Rebeca Isabel, "Assessing the Use of Tsunami Simulations as a Tool to Predict Source Magnitudes and Locations of Paleoearthquakes in Chile" (2018). All Master's Theses. 947.
https://digitalcommons.cwu.edu/etd/947

Language

English