Seismic Tomography of the Lithosphere with Body Waves

Abstract

A pair of papers in 1976 lead-authored by Kei Aki heralded the beginning of the field of seismic tomography of the lithosphere. The 1976 paper by Aki, Christoffersson, and Husebye introduced a simple and approximate yet elegant technique for using body-wave arrival times from teleseismic earthquakes to infer the three-dimensional (3-D) seismic velocity heterogeneities beneath a seismic array or network (teleseismic tomography). Similarly, a 1976 paper by Aki and Lee presented a method for inferring 3-D structure beneath a seismic network using body-wave arrival times from local earthquakes (local earthquake tomography). Following these landmark papers, many dozens of papers and numerous books have been published presenting exciting applications of and/or innovative improvements to the methods of teleseismic and local earthquake tomography, many by Aki's students.This paper presents a brief review of these two types of tomography methods, discussing some of the underlying assumptions and limitations. Thereafter some of the significant methodological developments are traced over the past two and a half decades, and some of the applications of tomography that have reaped the benefits of these developments are highlighted. One focus is on the steady improvement in structural resolution and inference power brought about by the increased number and quality of seismic stations, and in particular the value of utilizing shear waves. The paper concludes by discussing exciting new scientific projects in which seismic tomography will play a major role -the San Andreas Fault Observatory at Depth (SAFOD) and USArray, the initial components of Earthscope.

Inferring crustal structure in the Aleutian island arc from a sparse wide‐angle seismic data set

“…Seismic travel time tomography is generally regarded as an objective tool for interpreting travel time data [ Iyer and Hirahara , 1993; Thurber , 2003], although differences exist between implementations [ Phillips and Fehler , 1991; Zelt , 1999]. The technique starts with the choice of an appropriate reference model in which rays are traced between the sources and receivers.…”

Imaging of Lithospheric Structure Beneath Jeju Volcanic Island by Teleseismic Traveltime Tomography

“…However, due to a lack of geophysical studies, the origin and magmatic processes of volcanism in JI have not been confirmed. the region of interest and sampling velocity variations inside the modeled space (Aki et al, 1977;Lévêque & Masson, 1999;Thurber, 2003). This method has provided useful information on unrevealed localized upper mantle structures, for example, in Northeast (NE) Asia (e.g., Chen et al, 2017;Lei & Zhao, 2005;Ma et al, 2018;Zhao et al, 2009).…”

“…Tomographic approaches using data on the relative traveltime of teleseismic body waves have been used to image upper mantle structures from continental scales (e.g., Argnani et al, ; Biryol et al, ; Schmandt & Lin, ) to regional scales (e.g., Bastow et al, ; Rawlinson & Kennett, ; Schlömer et al, ). This method has been successful in revealing detailed three‐dimensional (3‐D) velocity heterogeneities beneath seismic arrays by taking advantage of individual rays from a common event sharing the same path outside of the region of interest and sampling velocity variations inside the modeled space (Aki et al, ; Lévêque & Masson, ; Thurber, ). This method has provided useful information on unrevealed localized upper mantle structures, for example, in Northeast (NE) Asia (e.g., Chen et al, ; Lei & Zhao, ; Ma et al, ; Zhao et al, ).…”

Advances in seismic imaging of magma and crystal mush

“…Kounoudis et al, 2021). For a more complete comparison of LET and TST see Thurber (2003). A detailed discussion of TST applications to imaging volcanoes can be found in Iyer and Hirahara (1993).…”