SURFACE‐WAVE DISPERSION APPLIED TO THE DETECTION OF SEDIMENTARY BASINS

Abstract

Seismic surface‐wave velocities are greatly affected by crustal structure. Because there is a strong contrast in the physical properties of clastic sediments and underlying basement materials, surface‐wave dispersion provides a fast, convenient, and inexpensive means of detecting sedimentary basins and estimating their thickness. Model calculations and published reports of explosion studies indicate that sedimentary thicknesses as shallow as 500 m (∼1650 ft) should be detectable by analysis of routinely recorded earthquake seismograms. This study demonstrates the use of seismic surface‐wave dispersion to detect sedimentary basins and to estimate their thickness. The technique is used first for the Mississippi embayment region of the U.S. Gulf Coast, where the crustal structure is known and the results can be verified, and then applied to offshore Greenland, where the crustal structure is unmapped but a sedimentary basin is suspected. The data used are available seismograms of natural earthquakes and, for the Gulf Coast area, an underground nuclear explosion. Because this technique requires only existing, readily available data and may be applied to many regions of the world, it offers an attractive reconnaissance tool in petroleum exploration. In the present study, surface‐wave dispersion and the effects of shallow crustal structure are reviewed in light of this application, and the advantages and limitations of the technique are explored.