1. 1. 2. 3. 4. 5. 6. 7. 8. 9. © Estimation Of Sand Dune Thickness Using A Vertical Velocity Profile Al-Shuhail, AA KING FAHD UNIV PETROLEUM MINERALS, ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING; pp: 145-153; Vol: 29 King Fahd University of Petroleum & Minerals http://www.kfupm.edu.sa Summary Previous field and mathematical studies have shown that sand dunes may have vertical velocity profiles (i.e., continuous increase of velocity with depth). Therefore, computing the dune's thickness using conventional seismic refraction methods that assume a vertically homogeneous layer will likely produce some errors. The purpose of this study is to quantify the effect of the vertical velocity profile in a sand dune on the process of thickness estimation using seismic refraction data. First, the time- distance (T-X) data of the direct wave in the dune is calculated using a vertical velocity profile, V(z), derived from Hertz-Mindlin contact theory. Then, the thickness is estimated from the calculated T-X data, intercept time, and velocity of the refractor at the dune's base assuming a constant velocity in the dune. The error in the estimated thickness due to the constant-velocity assumption increases with increasing thickness and decreasing porosity of the dune. For sand dunes with porosities greater than 0.2 and thicknesses less than 200 m, the error is less than 15%. References: ACHESON CH, 1963, GEOPHYSICS, V28, P894 ALCHALABI M, 1997, GEOPHYS PROSPECT, V45, P715 ALCHALABI M, 1997, GEOPHYSICS, V62, P270 ALCHALABI M, 1997, GEOPHYSICS, V62, P970 ALCHALABI M, 2001, GEOPHYS PROSPECT, V49, P645 ALSHUHAIL AA, 2002, J SEISM EXPLOR, V11, P383 BACHRACH R, 1998, GEOPHYSICS, V63, P1234 BANTA HE, 1941, GEOPHYSICS, V6, P245 BERRY MJ, 1971, J GEOPHYS RES, V76, P6464 Copyright: King Fahd University of Petroleum & Minerals; http://www.kfupm.edu.sa

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