Geophysics - Seismic Processing

An Introduction to Velocity Model Building



  Dr Ian Jones (ION, London, United Kingdom)


  1 or 2 days


  Geophysics – Seismic Processing






  5 or 10 CPD points




Introduction video

A short version of this course has been recorded as an E-Lecture. Watching this video will give you a clear introduction of what the course is about and it will help you to prepare yourself if you are going to attend it!

Learn more about EAGE E-Lectures


Course description

The course will begin with a review of migration theory, emphasizing those aspects that affect our ability to build a velocity model of the subsurface and indicating when time migration should be replaced with depth migration (and what specific type of depth migration should be used). Ray theory and wave theory will be mentioned, in terms of how the scale length of a velocity anomaly versus the wavelength of the sound illuminating interacts. We will then cover the motivations for building detailed velocity models and briefly discuss the inherent limitations on our ability to build a detailed model. A review of anisotropy and of the principles of tomographic inversion will be given and current-day practice will be covered, exemplified via several case-studies. The approach will not be mathematical but rather will try to concentrate on an intuitive understanding of the principles and demonstrate them via case histories. This course will try to provide a complete overview but some topics such as VSP and multi-component data will not be covered.


Course objectives

The course objective is to provide the participants a firm understanding of the processes and assumptions involved in building velocity-depth models and of the limitations of various migration algorithms


Course outline

Why do we need a detailed velocity model?

  • Review of migration schemes
  • The limitations of time migration and benefits of depth migration
  • Snell’s law and how to ignore it
  • How does depth migration differ from time migration?
  • Is depth migration always necessary?
  • How accurate does an image need to be?

How detailed can we get?

  • Sources of uncertainty
  • Non-uniqueness and ambiguity
  • Limits on resolution

Model building through the ages

  • The iterative multidisciplinary approach
  • Tomographic update
  • Anisotropy versus heterogeneity (and other higher order moveout effects)

Current industrial practice

  • What does tomography need to accomplish?
  • Iterative model update
  • Layered, gridded and hybrid tomography
  • Complex water layers
  • Near-surface velocity anomalies

The Future: emerging R&D directions

  • Wavepath tomography
  • Waveform inversion


Participants' profile

Geophysicists with an interest in migration and velocity model building and geologists (with a basic knowledge of data processing) who wish to understand a bit more about how the images they look at are created.



Participants should have some knowledge of basic data processing.


About the instructor

Dr Ian Jones

Ian F. Jones received a joint honours BSc in Physics with Geology from the University of Manchester, UK, in 1977, an MSc in Seismology from the University of Western Ontario, Canada, and a PhD in Geophysical Signal Processing from the University of British Columbia, Canada. After working for ‘Inverse Theory & Applications Inc.’ in Canada for two years, he joined CGG, where for 15 years he was involved in R&D in the London and Paris offices, latterly as manager of the depth imaging research group. Since 2000 he has been with ION GX Technology, as a Senior Geophysical Advisor in their London office.

His interests include velocity model building and migration, and his most recent activity includes writing the text books: ‘Velocities, Imaging, and Waveform Inversion: the evolution of characterising the Earth’s subsurface’ published by the EAGE in 2018; ‘An Introduction to Velocity Model Building’ published by the EAGE in 2010; and co-editing the SEG Geophysics Reprints series volumes ‘Classics of Elastic Wave Theory’ and also ‘Pre-Stack Depth Migration and Velocity Model Building’, as well as contributing the chapter on model building to the new SEG online encyclopaedia.

He is an associate editor for the journals ‘Geophysics’ and ‘Geophysical Prospecting’, and teaches the EAGE/PESGB/SEG continuing education course on ‘Velocity Model Building’ and is an external lecturer at the University of Leeds and Imperial College London. Ian was awarded the EAGE’s Anstey Medal in 2003 for contributions to the depth imaging literature, made the SEG European Honorary Lecturer in 2012, conducted the 2018-2019 EAGE international Education Tour, and was made an Honorary Life Member by the EAGE in 2018.


Recommended reading

  • Jones, I.F, 2014, Tutorial: migration imaging conditions. First Break, accepted.
  • Jones, I.F, and Davison, I., 2014, Seismic imaging in and around salt bodies. SEG Interpretation, 2, no.4, SL1-SL20.
  • Jones, I.F, 2013, Tutorial: The seismic response to strong vertical velocity change. First Break, 31, no.6., 43-54.
  • Jones, I.F, 2013, Tutorial: Transforms, orthogonality, eigenvectors, and eigenvalues. First Break, 31, no.1., 51-61.
  • Jones, I.F, 2012, Tutorial: Incorporating near-surface velocity anomalies in pre-stack depth migration models. First Break, 30, no.3,
  • Jones, I.F, 2010, Tutorial: ray-based tomography. First Break, 28, no.2, 45-52
  • Jones, I. F., 2008, A modeling study of pre-processing considerations for reverse-time migration: Geophysics,. 73, NO. 6; T99—T106.
  • Fruehn, J.K., I. F. Jones, V. Valler, P. Sangvai, A. Biswal, & M. Mathur, 2008, Resolving Near-Seabed Velocity Anomalies: Deep Water Offshore Eastern India: Geophysics, 73, No.5, VE235-VE241..
  • Jones, I. F., 2008, Effects of pre-processing on reverse time migration — a North Sea study: First Break, 26, no.6, 73-80.
  • Jones, I.F., Sugrue, M.J., Hardy, P.B., 2007, Hybrid Gridded Tomography. First Break, 25, no.4, 15-21.
  • Farmer, P., Jones, I.F., Zhou, H., Bloor, R., Goodwin, M.C., 2006, Application of Reverse Time Migration to Complex Imaging Problems. First Break, 24, no.9, 65-73.
  • Jones, I.F., 2003, A review of 3D preSDM velocity model building techniques First Break, 21, no.3, 45-58.
  • Jones, I.F., Fruehn, J., 2003, Factors affecting frequency content in 3D preSDM imaging, : The Leading Edge, 22, no.2,.128-134.


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