Toward the Understanding of the 2018 Arnold, NE Earthquake Cluster: Relocation of Hypocenters and Establishment of New Gravity Base Stations

Authors

Kris Guthrie, University of Nebraska-LincolnFollow

First Advisor

Dr. Irina Filina

Date of this Version

3-2022

Document Type

Article

Citation

Guthrie, K., 2022, Toward the Understanding of the 2018 Arnold, NE Earthquake Cluster: Relocation of Hypocenters and Establishment of New Gravity Base Stations [Master's Thesis]: University of Nebraska-Lincoln, 126 p.

Comments

A Thesis Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Earth and Atmospheric Sciences, Under the Supervision of Professor Irina Filina. Lincoln, Nebraska: March, 2022

Copyright © 2022 Kris Guthrie

Abstract

In 2018, 27 unexpected earthquakes occurred in central Nebraska near Arnold. These earthquakes have no readily apparent cause and no evidence of the responsible fault system is seen at the surface. A joint analysis of vintage, regional gravity and magnetic datasets before the first earthquake revealed a lineament that could represent a pre-existing fault system. New high resolution potential fields data are needed to confidently map the subsurface features around the cluster. To design a survey and collect the data, the following tasks need to be addressed: [1] The earthquakes’ hypocenters need to be improved (relocated) to increase the efficiency of the geophysical survey. [2] Establishing an easily accessible, public, absolute gravity base station is necessary for the future Arnold survey. [3] A literature review of potential triggers of the Arnold earthquakes is needed. This project achieved all three objectives. The earthquakes’ hypocenters were relocated which resulted in tighter clustering. Two new gravity base stations were established on the UNL campus by transferring absolute gravity values from four existing stations. The Bell Tower station’s absolute gravity value is 980177.760 mGal ± 0.082 mGal and the Museum station’s value is 980178.035 mGal ± 0.096 mGal. The literature review did not reveal any apparent trigger for the Arnold earthquakes.

Advisor: Irina Filina