Image-based modeling for statics corrections and velocity uncertainty in near-surface complex structures

Öz Yilmaz
Wednesday, March 29, 2017 · 4:00 pm
ESB 5104

In exploration seismology, the most common type of the near-surface is defined as the depth interval below the topography, composed of a low-velocity, unconsolidated, heterogeneous soil column and weathered rock layer. As such, raypaths are close to vertical incidence within the near-surface --- a requirement for statics corrections to be acceptable. This definition of the near-surface does not apply to the case of a rock outcrop. Hence, if it is near the surface, it is not always the near-surface within the context of the definition above. In contrast with the near-surface defined above, the subsurface is composed of relatively higher velocity, consolidated rock layers. As such, the interface between the near-surface and the subsurface often gives rise to a strong shallow reflection. I shall describe an image-based method, which makes use of the strong reflection at the base of the near-surface, to estimate a model for the near-surface for statics corrections. In areas with complex near-surface with irregular topography and complex subusrface, there is much uncertainty in rms velocity estimation for prestack time migration, whereas interval interval velocity estimation for prestack depth migration is despairingly challenging.  Rather than struggling to eliminate the velocity uncertainty completely --- an impossible task, a workflow is presented to circumvent the velocity uncertainty.  These routes are demonstrated using a field data set from an onverthrust belt.

Öz Yilmaz is a world-reknown geophysicist. He graduated from Haydarpasha Lyceum in Istanbul and subsequently completed a BS in geology with geophysics from University of Missouri-Rolla. He received an MSc in 1972 from Stanford University working on rock physics, and in 1979, a PhD in exploration seismology from Stanford. His dissertation on prestack partial migration was a major contribution to seismic processing.

In 1987 Dr. Yilmaz published "Seismic Data Processing" through the Society of Exploration Geophysicists, which became a standard reference volume in the field of seismic processing theory. In 1991 he was awarded the Conrad Schlumberger Award by the European Association of Geoscientists and Engineers for "his sustained contributions to the theory and practice of seismic data processing". In 2001 Dr. Yilmaz published the follow-up two volume "Seismic Data Analysis" which incorporated emerging technologies in seismic exploration such as 3D seismic, time-lapse seismic, and 4-component seismic. His third book entitled "Engineering Seismology" was published by the SEG in 2015.

Dr. Yilmaz started his professional career at the Turkish Petroleum Company, later working for Western Geophysical and Paradigm. He is the founder of Anatolian Geophysical and currently Chief Technology Officer of GeoTomo LLC.