Crustal Structure of the Vøring Plateau and Vøring Spur from Joint Refraction and Reflection Travel-time Tomography

Authors

• Anika Nawar Mayeesha, University of Nebraska-LincolnFollow

First Advisor

Irina Filina

Committee Members

Erin Haacker, Christian Huebscher

Date of this Version

7-2026

Document Type

Thesis

Citation

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, July 2026

Comments

Copyright 2026, Anika Nawar Mayeesha. Used by permission

Abstract

Crustal architecture of the Vøring Plateau and Vøring Spur in the mid-Norwegian continental margin remains debated because the geophysical data in the area do not uniquely constrain whether the crust is continental, oceanic, or transitional. This study reanalyzes wide-angle ocean-bottom seismometer data from Profile 11-03 across the Vøring passive continental margin using joint travel-time tomography of crustal refractions and Moho reflections. A total of 6,760 first-arrival picks and 542 PmP picks from sixteen instruments were inverted for P-wave velocity and reflector depth. Three starting models were inverted independently to test sensitivity to the initial crustal configuration. The first two used laterally varying Moho geometries, reaching depths of approximately 10 and 15 km in the northwestern part of the model, whereas the third used a flat Moho at 20 km depth. Despite initial root-mean-square residuals of 1040, 650, and 500 ms, all models converged to final residuals of 65-66 ms, a normalized chi-squared of 0.95, and a mean residual of −0.001 s. Where sampled by PmP reflection points, the reflector lies at 14–20 km below sea level, and the three scenarios agree within 0.3–1.0 km, indicating that reflector geometry is controlled by the data. Because the tomography of crustal refractors did not resolve a strong velocity contrast along much of the Moho reflector, additional inversions were performed in which velocities beneath the reflector were reset to 8.1 km/s after each iteration. This imposed upper mantle velocity produced a clearer crust–mantle contrast while leaving the data-constrained velocity structure above the reflector and the resolved reflector geometry unchanged. A final model was obtained by averaging the three converged scenarios. It contains sedimentary velocities increasing from about 2.0 km/s at the seafloor to 4.0 km/s near basement, upper-crustal velocities of 4.5–6.5 km/s, and a high-velocity lower crust reaching 7.5 km/s beneath the Vøring Plateau and Vøring Spur. Comparison with Breivik et al. (2014) shows a broad agreement in Moho geometry along the northwestern and southeastern profile, with an approximately 2 km difference in the central region likely related to contrasting parameterization and regularization of two different methodologies. The maximum lower-crustal velocity derived in this study exceeds the ~7.2 km/s reported by Breivik et al. (2014) but agrees with 7.4–7.5 km/s velocities from tomographic models of the conjugate East Greenland margin and Greenland–Iceland Ridge. The resulting model provides a data-constrained framework for future integration with gravity and magnetic observations to evaluate crustal affinity and refine the ocean–continent boundary beneath the Vøring Plateau and Vøring Spur.

Advisor: Irina Filina