Simultaneous Inversion of Reflection and Refraction Seismic Data and Application to Field Data From the Northern Rio Grande Rift

Abstract

S U M M A R YAn inversion scheme that determines a velocity model simultaneously from normalincidence reflection and refraction/wide-angle reflection seismic data has been developed, tested, and applied to real seismic data. Simultaneous inversion minimizes the non-uniqueness of inversion results. A common midpoint (CMP) stacked reflection section provides a detailed image of the structural configuration in time. Refraction or wide-angle reflection data can be used to derive a velocity model. If both refraction data and normal-incidence reflection data are available along coincident profiles, simultaneous inversion of the data sets can produce an improved model. With the extra control of the interface depth provided by reflection data, it is also possible to avoid ambiguity of phase identification. The commonly used damped-least-squares (DLS) inversion method often results in significant inversion artefacts. We provide effective methods for reducing inversion artefacts using both damping and smoothing. From tests using synthetic data, we conclude that the simultaneous inversion scheme can improve resolution and can be applied to velocity models with a reasonably complex structure. The simultaneous inversion scheme has been successfully applied to coincident seismic reflection and refraction data recorded by the SAGE program in 1990-1991 in the western boundary area of the Rio Grande rift near Abiquiu, New Mexico. In this example, the simultaneous inversion derived a velocity model in which stratigraphic units and extensional fault blocks can be resolved.

Seismic Traveltime Tomography of the Crust and Lithosphere

“…Authors who have used DLS solutions to invert wide-angle traveltimes include Kanasewich & Chiu (1985), Chiu et al (1986), Farra & Madariaga (1988), White (1989), , , Zelt & Smith (1992), Lutter et al (1994), Kosloff et al (1996), Wang & Braile (1996), McCaughey & Singh (1997) and Zelt & Barton (1998). Similarly, DLS is also popular in local earthquake tomography (Aki & Lee, 1976;Thurber, 1983;Eberhart-Phillips, 1986;Graeber & Asch, 1999).…”

“…Laterally discontinuous structures like those found at subduction zones (Zelt, 1999) can be represented because interfaces tend to have a shallow dip and layer dislocation is not usually needed. Wang & Braile (1996), using a method based on that of Zelt & Smith (1992), represent faults implicitly by sharp near-vertical jumps in sub-horizontal interface structure in adja-cent interfaces. However, these structures were constrained manually during the inversion process.…”

“…Aki et al, 1977;Benz et al, 1992;Steck et al, 1998), wide-angle traveltime inversions (e.g. White, 1989;Hole, 1992;Zelt & Smith, 1992;Riahi & Lund, 1994;Wang & Braile, 1996) and local earthquake tomography studies (e.g. Eberhart-Phillips, 1990;Eberhart-Phillips & Michael, 1993;Abers, 1994;Protti et al, 1996;Graeber & Asch, 1999).…”

“…For example, numerous studies have been carried out in Canada (e,g, Hole et al, 1992;Kanasewich et al, 1994;Clowes et al, 1995;Zelt & White, 1995;Morozov et al, 1998;Zelt et al, 2001), the U.S. (e.g. Jarchow et al, 1994;Zhu & Ebel, 1994;Parsons et al, 1996;Wang & Braile, 1996;Lizarralde & Holbrook, 1997), Europe (e.g. Riahi & Lund, 1994;Staples et al, 1997;Darbyshire et al, 1998;Louden & Fan, 1998;Mjelde et al, 1998;Korenaga et al, 2000;Morgan et al, 2000) and in oceanic settings (e.g.…”

“…Thurber (1983) and Ankeny et al (1986) included refraction traveltimes from several explosive sources in a LET study, Parsons & Zoback (1997) simultaneously inverted local earthquake, explosive source and airgun traveltimes for the crustal structure of the San Francisco Peninsula, and Sato et al (1996) simultaneously inverted local earthquake and teleseismic traveltime data to image structure beneath the northeastern Japan arc. Methods that combine coincident reflection and wide-angle data in a simultaneous inversion have been developed by Wang & Braile (1996) and McCaughey & Singh (1997).…”