Premium
MULTIPLE REFLECTIONS AND HEAD WAVES IN THE GULF OF SUEZ *
Author(s) -
DOMENICO S. N.
Publication year - 1979
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/j.1365-2478.1979.tb00984.x
Subject(s) - geology , reflection (computer programming) , reflection coefficient , refraction , attenuation coefficient , mineralogy , intensity (physics) , seismology , geodesy , optics , geophysics , physics , computer science , programming language
A bstract Inferior reflection quality in the Gulf of Suez at the target depth interval is attributable in part to surficial multiple reflections. An excellent example of the latter is observed on a typical seismic line in the northern portion of the Gulf. An increase in prominence of the multiple reflections appears associated with decreasing depth to a dipping highvelocity layer. Inversion of a second‐order polynomial time‐distance function, fitted to the observed refraction onset time‐distance values, gives the velocity‐depth function for sediments between the water bottom and a high‐velocity layer. Velocities thus determined increase non‐linearly with depth from a value near water velocity at the water bottom. Depths to the high‐velocity layer are obtained from the associated head‐wave linear time‐distance function and by ray tracing in the overlying sediments. As the high‐velocity layer approaches the water bottom from sub‐water depths exceeding 0.6 km to a depth of 56 m, intensity of the multiple reflections increases to the extent of completely dominating individual records to a time of at least 3 s. The estimated plane‐wave normal‐incident reflection coefficient at the top of the high‐velocity layer increases with decreasing depth to this layer, approaching 0.5 at the shallowest depth. This strong reflection coefficient further substantiates the existence of multiple reflections between the high‐velocity layer and water layer. However, existence of water‐layer multiples cannot be ruled out. The estimated water‐bottom reflection coefficient is approximately 0.3, a substantial value. Multiple reflections of considerably less intensity are apparent where the high‐velocity layer is deepest, and it is likely that such are waterlayer multiple reflections. Unfortunately, water‐layer multiple reflections and multiple reflections between the water surface and high‐velocity layer cannot be separated by their coincidence with time‐distance (normal moveout) curves, the configuration of each visibly matching the curves equally well.