Honors Program
Honors Program: Theses
First Advisor
Irina Filina
Date of this Version
Spring 3-31-2025
Document Type
Thesis
Citation
Madsen, M. 2025. Integrated Geophysical Modeling of Newly Identified Pseudofaults within Southern Cascadia Subduction Zone. Undergraduate Honors Thesis. University of Nebraska-Lincoln.
Abstract
The Cascadia Subduction Zone, located off the western coast of North America, has a long history of seismic activity, causing various geohazards such as megathrust earthquakes and tsunamis for the coastal population (Goldfinger et al., 2000; Tréhu et al., 2022). It is necessary to identify areas of greater risk, as seismic hazards will continue to affect the area due to ongoing subduction of the oceanic Juan de Fuca plate beneath the North American continent. Heavily fractured, weakened zones of oceanic crust, known as propagator wakes and pseudofaults, have been shown to correlate with greater seismicity (Ashraf and Filina, 2023a). Propagator wakes have been established in the area by mapping magnetic chron data (Wilson, 2002). However, magnetic data in the area was revisited recently and showed that some smaller features had not been mapped (Ashraf, 2021; Madsen and Filina, 2023). This study uses integrated geophysical analysis to map and model two newly identified pseudofaults in Southern Cascadia. Our modeling shows that the observed pseudofaults correspond to areas of lower-density crust. In addition, one of the pseudofaults is aligned with an earthquake that occurred in the subducting slab, which shows strike-slip motion. Moreover, the identified features also correlate with known landslide complexes in this region, suggesting seismic activity in the past (Goldfinger et al., 2000). The connection to seismic activity underscores the importance of mapping these features and understanding their properties.
Comments
Copyright Morgan R. Madsen 2025