CWU Geologists Awarded $267,194 to Study Megathrust Earthquakes

Two CWU geology professors, Lisa Ely and Breanyn MacInnes, have received more than a quarter of a million dollars to study historic geological data in south-central Chile in order to better understand and assess the effects of powerful earthquakes and tsunamis, like those that occur in the Northwest.

According Ely, Chile’s earthquake zone is almost a mirror image to the Pacific Northwest’s Cascadian subduction zone, with a similar history of megathrust earthquakes and tsunamis.

“Understanding how these massive earthquakes occur, and what the accompanying tsunamis entail helps us understand what has happened—and what could possibly happen—in the Northwest,” Ely said.

Based on information gleaned in the field, MacInnes will develop computer simulations of tsunamis that could result from different megathrust fault ruptures to estimate the size and location of earthquakes in the last 2,000 years.

By working backwards from the evidence left in layers of sand and dirt, and in the tiny fossil shells of diatoms (a unique form of algae), investigators will try to deduce the origin and number of tsunamis in a particular area. They also hope to calculate the magnitude and characteristics of the ruptures and earthquakes.

The grant will employ two methods to investigate the parameters of past megathrust earthquakes. First, their co-principle investigators from Rutgers University will study diatom fossils that are found throughout layers of sediment. Diatoms have a hard silica shell, and their shell patterns are specific to each species of diatom. Scientists can tell whether a specimen is a salt-water or fresh-water diatom, thus determining which sediment layers were deposited by tsunamis and whether land was thrust upward, or fell precipitously in the course of the earthquake.

Secondly, Ely and her colleagues will study strata of sand and dirt deposits in various areas along the coastline—“by looking at river cuts, digging pits, and taking core samples,” she explained. “In any one place one might have deposits from up to eight tsunamis over several thousands of years.” They will also study how long tsunami deposits persist in a landscape over time. Much of this work will be based on previous work by Ely and her colleagues in 2009-2015, where they recorded sedimentary evidence of past earthquakes and tsunamis..

The massive, 8.8 magnitude Chilean earthquake that occurred in 2010 will provide an excellent test case for this study, since that event was recorded and surveyed. CWU graduate student Alexandra Ruiz based her master’s thesis using the same computer modeling technique to simulate the tsunami from the 2010 earthquake. “Her work was helpful in developing our project,” said Ely.

In addition, Ely and a Chilean colleague, Marco Cisternas, are developing a bilingual handbook on tsunami survival with a modern communication interface and information relevant to today’s technology. Cisternas is a professor at the Universidad Católica de Valparaíso, Chile.

Ely and MacInnes received $267,194 from the National Science Foundation for their three-year research project, “Collaborative Research: Application of Paleoseismic Evidence and Tsunami Simulations to Quantify Megathrust Rupture Characteristics, South-Central Chile.” They will receive $83,554 for the first year’s work.

Photo: Tina Dura, of Rutgers University, and Lisa Ely, CWU, examine tsunami deposits at Tirúa, Chile. Photo by Robert Wesson

Media Contact: Valerie Chapman-Stockwell, Public Affairs, 509-963-1518, valeriec@cwu.edu

August 30, 2016