Influence of Scattering on Seismic Waves: Velocity and Attenuation of the Upper Crust in Southeast Maine

Abstract : Rg and Pg velocities and Rg attenuation have been examined for the Central Merrimack Synclinorium and nearby regions in southeastern Maine using digital records from a seismic refraction experiment. Determination of Rg group velocities and Pg travel times indicates that both lateral variations and azimuthal anisotropy are present in the study area. The axes of the axes of the azimuthal velocity anisotropy appear to lie along and perpendicular to the Appalachian structural strike in the region, with Rg group velocities along strike up to 20% faster than cross strike velocities. Measurement of Rg attenuation gives Q values of 25-80, varying with frequency. Inversion of the Rg group velocity for velocity structure shows that both the compressional and shear velocities increase rapidly with depth in the upper 1 km in the region. Keywords: Short period Rayleigh waves, Anisotropy, Earth crustal structure, Seismic wave attenuation, New England.