Senior Project Advisor

Emily Roland

Document Type


Publication Date

Spring 2024


seismology, tectonics, tomography, seismic refractions


The Queen Charlotte Fault (QCF), located offshore of southeastern Alaska and western British Columbia, accommodates ~5 cm/year of right-lateral strike-slip between the Pacific and North American plates. This fault has generated several magnitude (>7) earthquakes, the most recent being a magnitude 7.5 Craig earthquake in 2013. Analyzing characteristics of damage zones and tectonically influenced subsurface geology surrounding the QCF fault trace, we present a seismic velocity model of a 147 km transect that crosses the approximate epicenter of the Craig earthquake. Ultra-long offset seismic streamer-recorded refractions sample the upper crust and are compiled for first-arrival travel-time tomography. Relatively shallow water (<0.5 km) along the eastern half of the transect allows for shallow first-arrival ray coverage without the need for downward continuation. First-arrival energy is delayed by ~0.2 s in a 0.5 km-wide zone surrounding the principal slip surface, possibly related to a narrow low-velocity zone. Ray tracing and travel-time inversions were conducted jointly with crustal first-arrival picks on 16 ocean-bottom seismometers for higher-resolution imaging surrounding the fault trace. Here, we present a high-resolution P-wave velocity model that constrains the upper crust to identify potential low-velocity zones in the upper seismogenic zone of the Craig earthquake region. Final modeling shows little evidence of a pervasive low-velocity zone around the principal slip interface. Instead, velocities resolved around the fault zone are higher than expected, and the present low-velocity features lie to the west of the fault trace.






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