Date of Award
Open Access Thesis
Earth and Ocean Sciences
Thomas J. Owens
Shear-coupled P-waves have been shown to possess great utility in resolving crustal and upper mantle models, however these phases remain largely untapped due to their ephemeral nature. Shear-coupled P-waves are a type of seismic phase that undergo S-to-P conversion either at the free-surface or at the base of the crust. Under the proper conditions, it is possible for the converted crustal P phases to achieve total internal reflection, allowing these phases to remain large in amplitude and sample long segments of the crust. In this study, we use a combination of real-world observations collected from literature, and synthetic seismograms, to constrain the parameters that allow for observable shear-coupled P-waves to be generated.
The primary controls we investigate are source distance, source depth, and teleseismic S-wave polarization. By examining observations within real data and generating synthetic seismograms, we find that for epicentral distances between 32 and 55 degrees, the incoming S-wave has an angle of incidence that allows for converted phases to achieve total internal reflection; source depths greater than 100km produce depth phases that do not interfere with the S-coda; and incoming S-waves that are more vertically polarized convert more energy into crustal P-waves. After determining the range of parameters that reliably produce observable shear-coupled P-waves, we then develop an atlas of locations where shear-coupled P-waves are most likely to be observed.
Finally, we use our atlas of shear-coupled P-wave observability, informed by our newly constrained controls, to search preexisting data for new observations of shearcoupled P-waves.
Saftner, J.(2022). Quantifying the Controls of Shear-Coupled P-Waves. (Master's thesis). Retrieved from https://scholarcommons.sc.edu/etd/6818