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

Abstract

Seismic refraction methods are used in environmental and engineering studies to image the shallow subsurface. We present a blind test of inversion and tomographic refraction analysis methods using a synthetic first-arrival-time dataset that was made available to the community in 2010. The data are realistic in terms of the near-surface velocity model, shot-receiver geometry and the data's frequency and added noise. Fourteen estimated models were determined by ten participants using eight different inversion algorithms, with the true model unknown to the participants until it was revealed at a session at the 2011 SAGEEP meeting. The estimated models are generally consistent in terms of their large-scale features, demonstrating the robustness of refraction data inversion in general, and the eight inversion algorithms in particular. When compared to the true model, all of the estimated models contain a smooth expression of its two main features: a large offset in the bedrock and the top of a steeply dipping low-velocity fault zone. The estimated models do not contain a subtle low-velocity zone and other fine-scale features, in accord with conventional wisdom. Together, the results support confidence in the reliability and robustness of modern refraction inversion and tomographic methods.

Application of Frequency-dependent Traveltime Tomography and Full Waveform Inversion to Realistic Near-surface Seismic Refraction Data

“…This paper uses the realistic synthetic near-surface velocity model in Zelt et al (2013) and extends the discussions by incorporating waveform data and using a combined workflow of FDTT and FWI. The results and extended discussions in this paper 1) confirm the suitability of using IFTT/FDTT to provide the starting model for FWI, 2) demonstrate the ability of FDTT to produce a more accurate starting velocity model for FWI to mitigate the lack of low frequency data, 3) show the improvement in model estimation using a combined strategy of FDTT and FWI, and 4) promote the use of FDTT and FWI in near-surface studies given the modest experiment and data requirements of refraction surveys over conventional reflection surveys.…”

“…In this paper, we test FDTT and FWI using a synthetic dataset generated from a realistic near-surface velocity model ( Fig. 1(a)) that was used previously in a blind test of first-arrival-time inversion and tomography methods (Zelt et al, 2013). The estimated velocity models from ten participants in the blind test using eight different inversion algorithms are generally consistent in their large-scale (.wavelength) features, but show only smooth expressions of the true model's key features ( Fig.…”

Interferometría de ruido sísmico para la caracterización de la estructura de velocidad 3D de un talud en la 3ª Sección del Bosque de Chapultepec, Ciudad de México

“…En este método se construye un modelo de estructura del subsuelo con las variaciones de velocidad producidas por el ajuste de los tiempos de viaje observados con aquellos derivados por el trazado de rayos. (Sheehan et al, 2005;Zelt et al, 2013). Aplicamos esta técnica de inversión mediante el módulo DWTomo del Software Geogiga Seismic Pro 6.0 ® .…”

Assessing uncertainty in refraction seismic traveltime inversion using a global inversion strategy

“…Furthermore, the resulting model typically includes no quantitative estimation of uncertainty, resolution, and non‐uniqueness issues (e.g., Zelt et al . ).…”

“…Generating a single solution (i.e., velocity model) explaining the observed travel time data is not necessarily demonstrating the correctness of the model or that the resulting model is the most probable solution (Palmer 2010b). Furthermore, the resulting model typically includes no quantitative estimation of uncertainty, resolution, and non-uniqueness issues (e.g., Zelt et al 2013).…”