SURFACE WAVES DISPERSION OF NORTH AND ORTHWESTERN IRAQ

Abstract

Surface waves have been used to estimate velocity variations within the earth at different scales, from small scale site characterization for engineering purposes to global tomography of surface waves dispersion data. Generally group velocities of surface waves along the bath from epicenter to recording give the average structure along the bath. In this study, dispersion parameter extracted from surface wave waveforms where inverted for crustal structure with great success, using least square inversion technique. Group velocity at 10, 15, 20, and 30s periods were obtained and mapped. Group velocities of Rayleigh waves vary between 2. 229-2.768 km/s in 10s period, 2.461-2.857 km/s in 15 s period, 2.581-2.944 km/s in 20s period and 2.789-3.656 km/s in 30s period accordingly. The group velocities agree well with expected low group velocity values of the Mesopotamia, they seem to reflect clearly the effect of thick sediment of the study area. Results are shown in 2D and 3D representation and generally agree with known or expected results from available models derived from global or regional geophysical studies.