2012


Calvin Johnson

Calvin Johnson


Years participated in RESESS:
2011
2012


An Overview

Major: Geoscience
Academic Affiliation: Pennsylvania State University
Research Mentor: Michael Brudzinski, MU
Postdoctoral Student Mentor: Harmony Colella, MU
Graduate Student Mentor: Kristen Schlanser, MU


Biography

Calvin grew up in Warner Robins, Georgia, where he graduated with honors from Northside High School. He decided to pursue a degree in Mathematics at Fort Valley State University, Georgia. He will then work towards a dual degree in geophysics at the University of Texas in Austin. His passion for geoscience was sparked by his first geology course. Calvin enjoys reading, going to the mall, watching movies, or relaxing and reflecting on life.


Abstract

Crustal structure of the Eastern United States from regional network recordings of wide angle Moho reflections

The EarthScope USArray is a collection of 400 seismometers being deployed in a uniform grid that is leapfrogging across the nation over 10 years. While these efforts are helping to refine known tectonic features in the western U.S., the impact on our understanding of the crustal structure in the eastern U.S. will be dramatic. This region has been poorly resolved, as the existing seismic recordings have occurred on a patchwork of local networks with less than ideal instrumentation for typical crustal imaging. In this study, we seek to utilize optimal teleseismic events (large, deep, simple source), which generate large wide-angle topside reflections off of the Moho (SsPmp). By applying this technique on instruments across the range of existing local networks, we have constructed a preliminary estimate of the crustal structure in the eastern U.S. that can advise us on where to focus additional instrumentation (i.e., Flex Arrays) in advance of USArray. We find thinner crust east of the topographic axis of Appalachia consistent with the presence of a more recently accreted terrane. We also find thinner crust along the Gulf Coast regions, as well as a region that extends up into the New Madrid seismic zone. The latter is consistent with a major failed rifting event. Curiously, some of the largest crustal thicknesses observed in the eastern U.S. occur in a region near Lake Erie, which could represent fossilized overthickening during the Grenville orogeny.