oa Seismic Refraction Shootout: Presentation of True Model and Comparison with Estimated Models

The purpose of this session is to provide an opportunity for all interested scientists to better understand the options and trade-offs involved in creating seismic velocity models from refraction travel time data. Submissions were encouraged from students new to seismic work, along with experienced experts. in this presentation, the true model will be revealed, along with quantitative comparisons with the estimated models presented during the session at the same scale and with the same display parameters. the accuracy of each final model will be discussed in some detail. the synthetic data consist of P-wave travel times for a seismic refraction experiment through a velocity model that represents a realistic near-surface geologic situation. Though not specifically intended to represent a karst environment, aspects of the model are consistent with a karst environment. there are unconsolidated, or semi-consolidated, sediments overlying a non-flat bedrock surface. the water table depth varies considerably in the area, between 20 and 100 m. there is zero surface topography along the seismic transect. the survey objective is to identify low velocity zones within the sedimentary layers, as well as features of the bedrock surface and within the bedrock. the travel times correspond to P-wave first arrivals, and were calculated assuming a 100 Hz wave. Uncorrelated Gaussianly-distributed noise with a standard deviation of 1 ms was added to the synthetic data. there are 101 shots from 0 to 300 m, and 100 receivers from 1.5 to 298.5 m. the shot and receiver spacing is 3 m. the total number of travel times is 10100.