Blind Test of Methods for Obtaining 2-D Near-Surface Seismic Velocity Models from First-Arrival Traveltimes

摘要

Seismic refraction methods are used in environmental and engineering studies to image theshallow subsurface. We present a blind test of inversion and tomographic refraction analysismethods using a synthetic first-arrival-time dataset that was made available to the community in2010. The data are realistic in terms of the near-surface velocity model, shot-receiver geometryand the data’s frequency and added noise. Fourteen estimated models were determined by tenparticipants using eight different inversion algorithms, with the true model unknown to theparticipants until it was revealed at a session at the 2011 SAGEEP meeting. The estimatedmodels are generally consistent in terms of their large-scale features, demonstrating therobustness of refraction data inversion in general, and the eight inversion algorithms inparticular. When compared to the true model, all of the estimated models contain a smoothexpression of its two main features: a large offset in the bedrock and the top of a steeply dippinglow-velocity fault zone. The estimated models do not contain a subtle low-velocity zone andother fine-scale features, in accord with conventional wisdom. Together, the results supportconfidence in the reliability and robustness of modern refraction inversion and tomographicMethods.