Ashley Grijalva

Ashley Grijalva

Years participated in RESESS:

An Overview

Major: Geophysics
Academic Affiliation: University of Texas at El Paso
Research Mentors: Craig Jones and Will Levandowski, CU
Writing Mentors: Will Levandowski and Lon Abbott, CU


Ashley grew up in El Paso, western Texas, also known as the Sun City. She currently attends the University of Texas at El Paso, where she enjoys the campus architecture modeled after Buddhist temples. Her interest in geology began during family hiking trips in the mountains of New Mexico. She gives credit to her former professor at UTEP for sparking an academic interest in the geological sciences.


Lateral Pn velocity and crustal thickness variations along six transects through the mid-continental United States

Different seismological investigations have suggested that the western edge of cratonic upper mantle lies somewhere within the Great Plains of the U.S. The creation and elevation of the Rocky Mountains and Great Plains is plausibly related to the modification or destruction of similar cratonic mantle that might have existed farther west. Thus, a better characterization of the nature of the transition from cratonic to tectonically active mantle at a regional scale might provide insight into this uplift episode. We examine Pn travel time residuals from earthquakes in the midcontinent recorded by EarthScope's Transportable Array to constrain the westernmost boundary of the North American cratonic mantle lithosphere. We picked Pn phase arrivals from ten regional events at stations up to 600 km distant around the craton edge. Where feasible, true Pn velocity and crustal thickness measurements were obtained along 20 reversed profiles between events. Low true Pn velocities (< 8.0 km/s) were found underlying Colorado, Wyoming, and New Mexico. In contrast, high Pn velocities (>8.0 km/s) exist to the east into Illinois and Oklahoma. The eastward increase in Pn velocities accompanies a decrease in crustal thickness from central Colorado to eastern Illinois. We will show observations helping to define the position of the boundary separating low Pn velocities to the west from high Pn velocities farther east that presumably reflect a colder and stable mantle lid. Results will be compared to published tomographic studies in the region to help understand the geometry of this boundary and place some constraint on its creation.