- Multiple earthquake events have been recorded off the coast of Oregon, yet their locations have great uncertainty. The largest source of uncertainty is the simple models of the crust that are used to interpret seismic recordings. Because the relationship between earthquake locations and crust are diagnostic of tectonic activity, it is important to determine accurate locations. Knowing how location estimates depend on an assumed crustal structure leads to a better understanding of earthquake activity. Using earthquake waveform data taken in Cascadia, arrival times of seismic waves were used to calculate the locations of three earthquakes. By assuming different crustal structures for the same earthquake, the impact of uncertainties in the structure on location were quantified. One-dimensional crustal structure models were used for three earthquakes: one thick model that had been used previously, and one thin model that better characterizes the crust in Cascadia. The thick crustal structure resulted in deeper earthquake locations while the thin model resulted in shallower locations. Although the thin crustal model resembles the region, the model yields a higher uncertainty than the thick model. While the exact location of the earthquakes is not known, comparing the models has allowed for a better understanding of the uncertainties.