C. H. Mehta

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C. H. Mehta
PhD Elementary Particle Physics
PhD university University of California

C. H. Mehta completed his Ph.D. in elementary particle physics from University of California in 1972. After teaching physics at Bombay University for three years, he joined the Oil and Natural Gas Corporation (ONGC) and retired in June 2005 as executive director and head of the Geodata Processing and Interpretation Centre (GEOPIC). As the head of GEOPIC, Mehta introduced several new technologies for processing and interpretating seismic data. He was a core member of a three-man committee for recommending exploration ventures of ONGC both in India and overseas. For the last two years, he has served the Society of Petroleum Geophysicists, India, as its vice president and was also a cochairman of the Technical Committee of Kolkata 2006 and Hyderabad 2008. He continues to serve SPG as the chief editor of its periodical, Geohorizons. He has also worked as director (consulting) at Paradigm Geophysical India, Mumbai, and taught seismic data processing and seismic stratigraphy as a visiting professor in earth sciences at the Indian Institute of Technology, Mumbai.

Mehta's research has spanned diverse areas: particle physics, atomic physics, search theory, and geophysics. In geophysics, his work has been in the areas of wave propagation in two-phase media, multiple suppression using wave equation, migration, maximum likelihood deconvolution (MLD) of seismic data, segmentation of well-log data using MLD, seismic facies classification using principle component analysis, seismic detection of basement fractures, extraction of Vp and Vs of sea bottom sediments, directivity correction, and QC of amplitudes for inversion of marine seismic data, etc. He has published several papers in these fields.

Mehta is a 1991 recipient of the prestigious National Mineral Award from the government of India and served as the 2009 SEG Honorary Lecturer, South and East Asia.

2009 SEG Honorary Lecturer, South and East Asia

Significance of Fresnel zones in seismic reflection prospecting

Seismic prospecting involves interpreting traveltime and amplitude anomalies. While the former can be understood using ray theory, the latter requires appreciation of the wave nature of the seismic propagation. In this context, the concept of Fresnel zones provides a handy, powerful tool–unencumbered by formidable mathematics–for understanding the relation between the lateral size of a subsurface anomaly and observed seismic amplitude. Starting with a brief historical review of wave theory, we discuss why wavefront propagates only forward, although Huygen’s construction also permits backward wave propagation. Using the concept of Fresnel zones, zero-offset seismic sections from a terminating reflector and a finite circular disk are discussed in detail and limits of vertical and lateral seismic resolution derived heuristically for finite S/N data. The presentation will bring out the importance of Fresnel zones not only in resolution studies but also for the correct determination of minimum migration aperture for optimum imaging.

Additional Resource

A recording of the lecture is available.[1]


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C. H. Mehta
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