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Explore the seismic refraction method used to study the La Bajada fault. Learn about data collection, models, and interpretations along with the detection of the fault's position and offset estimation. Findings suggest fault location, basalt layer depth, and displacement over time.
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Seismic refraction along a profile across the La Bajada fault Max Moorkamp
Outline • Seismic refraction method • Area of study and objectives • Data • Models and interpretation • Conclusions
Seismic refraction method • Uses refractions from interfaces to determine seismic velocities • At long distances the first arrival travels through deep layers • The Slope-Intersect-Method can be used to determine layer velocities and thickness • Results can be checked by calculating theoretical travel times from models
Slope intersect method • Determine slope and intersect of first arrivals • Each slope and intersect corresponds to one layer • Information from 2 different sites can be used to obtain dip of layers
Suspected fault position Area of study and objectives • Obtain velocity structure in the sub-surface • Determine position of the La Bajada fault • Estimate fault offset from position of basalt layer
Slope-Intercept Models Sites 221 - 401 Sites 281 – 457 Sites 161 - 341 Sites 101 – 281
Combined Models Sites 101 - 161 Sites 457 - 221 Basaltic rubble Loose Dirt Santa Fe Form. Quart. Sed. Basalt
Conclusions • The La Bajada fault is probably located between seismic sites 161 and 221 • The top of the basalt is only present to the west at a depth of 80 m • The displacement on the fault is 200 m in 4My