Seismic refraction traveltime inversion for static corrections in a glaciated shield rock environment: a case study |
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| Authors: | Heather Schijns Suvi Heinonen Douglas R Schmitt Pekka Heikkinen Ilmo T Kukkonen |
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| Institution: | Institute for Geophysical Research, Department of Physics, University of Alberta, Edmonton, Alberta T6G 2J1, Canada;, Institute of Seismology, University of Helsinki, PO Box 68, 00014 Helsinki, Finland;, and Geological Survey of Finland, PO Box 96, 02151 Espoo, Finland |
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| Abstract: | A traveltime inversion technique is applied to model the upper ～40 m of the subsurface of a glaciated shield rock area in order to calculate static corrections for a multi-azimuth multi-depth walk-away vertical seismic profile and a surface seismic reflection profile. First break information from a seismic refraction survey is used in conjunction with a ray-tracing program and an iterative damped least-squares inversion algorithm to create a two-dimensional model of the subsurface. The layout of the seismic survey required crooked seismic lines and substantial gaps in the source and receiver coverage to be accounted for. Additionally, there is substantial topographical variation and a complex geology consisting of glaciofluvial sediment and glacial till overlying a crystalline bedrock. The resolution and reliability of the models is measured through a parameter perturbation technique, normalized χ2 values, root means square traveltime residuals and comparison to known geology. |
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