Inverting every type of arrival for near-surface imaging
Inverting every type of arrival for near-surface imagingTuesday 19th September 2017
Social gathering starts at 5:00PM
Presentation starts at 5:30PM
In the past, imaging of the near surface by seismic surveys usually was restricted to inverting just one type of arrival, e.g. refraction travel times for 2D P-velocity tomograms or dispersion curves for 1D S-velocity models. The advent of multigigaflop laptop computers, cheaper channel counts, and dense recording arrays now allow for the inversion of almost every type of arrival in the seismic records. In this presentation, I will show how the modern methods of seismic interferometry, waveform inversion, and multidimensional surface-wave inversion can be used to effectively invert almost every type of arrival for shallow seismic imaging. I will present examples that show how (a) “super virtual interferometry” can double more than the offset of useable first-arrivals in refraction inversion by enhancing the SNR of far-offset traces, (b) “full waveform inversion” inverts the diving waves and refractions to give high-resolution P-velocity images, (c) “parsimonious seismic interferometry” decreases the acquisition time of refraction and surface-wave surveys by at least one order-of-magnitude, and (d) multidimensional inversion of surface-wave dispersion curves provides high-resolution estimates of the 2D shear-velocity tomogram to a depth of about the longest shear wavelength. I will present field data examples for hydrology applications, fault detection and earthquake hazards, and estimation of statics. All of these inversion methods can now be used for a single seismic survey with a sufficiently dense recording geometry.
Dr. Sherif M. Hanafy is a senior research scientist at KAUST. and is in charge of the geophysical field program (Seismology Lab). He teaches labs for geophysical field methods, seismic interferometry, travel time tomography, early arrival tomography, data interpolation/extrapolation, and shallow application of resistivity and GPR methods. He received his B.Sc. (1993) and M.Sc. (1996) degrees from Cairo University, Egypt in geophysics and then was awarded a Ph.D. from University of Kiel, Germany – Cairo University, Egypt (2002). He worked as an assistant professor at Cairo University (2002–2007). In 2004, he was awarded a one-year Fulbright scholarship at University of Utah. He went back to University of Utah for the second time as a post-doc (2007–2009), and in 2009, he moved to KAUST as a senior research scientist. In 2012, he was promoted to associate professor at Cairo University, Egypt. Dr. Hanafy is mainly interested in shallow application of geophysics for geologic, engineering, environmental, and archaeological application. He uses several geophysical methods in his work including seismic, electric, and GPR methods.