Date of Award:

8-2026

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Civil and Environmental Engineering

Committee Chair(s)

Brady R. Cox

Committee

Brady R. Cox

Committee

James A. Bay

Committee

Mohsen Zaker Esteghamati

Abstract

When two old electrical transmission towers in the Sacramento River Delta in California were demolished by Pacific Gas and Electric Company, Utah State University saw an opportunity hiding inside the demolition. Because one of the towers stood close to the Sacramento River and its protective levee, they used the controlled collapse not only to monitor strains in the levee and surrounding ground, but also to learn what lied beneath the ground surface.

To capture this event, the researchers buried a 1.4-kilometer fiber optic cable along the ground and connected it to a system called Distributed Acoustic Sensing (DAS), which can detect tiny vibrations at thousands of points along the cable. They also placed 130 small seismometers, called nodal stations, in linear and circular configurations around the site. Together, these instruments recorded the tower collapses, sledgehammer strikes, and the natural vibrations of the earth to develop images of the subsurface.

Using this data, the soil layers beneath the site were mapped to depths of up to 150 meters, revealing soft, weak ground near the surface that matched what previous soil boring logs had shown. This kind of information helps engineers understand how the ground might behave during earthquakes or other events.

A fiber optic cable and DAS technology can be used to measure ground strain, but not the speed of the ground’s motion the way a traditional seismometer does. So, this study also compared three different methods for converting the cable’s strain measurements into the more familiar measurement of particle velocity. It checked the accuracy of each method against the co-located nodal stations and found one of the methods, fk-rescaling, to be the most reliable. These results help guide engineers and researchers toward better tools for monitoring strains and characterizing soil conditions using fiber optic technology in future projects.

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