Seismic velocity and Q model for the shallow structure of the Arabian shield from short‐period Rayleigh waves

Abstract

The shear velocity and [Formula: see text] structure for the upper 1 km in different tectonic regions of the Arabian shield have been investigated using high‐frequency vertical component records of Rayleigh waves (1–20 Hz), which were recorded at source‐to‐receiver separations 55–80 km during a deep seismic refraction survey. Group and phase velocities of the fundamental and first higher modes were inverted for the shear‐wave velocity structure; Rayleigh‐wave attenuation coefficients were determined from the decay of the amplitude spectrum of the fundamental mode and used to invert for the [Formula: see text] structure. Models derived from the data were tested by calculating synthetic seismograms for the fundamental and the first higher modes from surface‐wave theory with a center of compression used to represent the source; both band‐pass filtered step and Dirac delta source time functions were tested. Modeling indicates that the shear‐wave velocity of the shield increases from 2.6 km/s to 3.4 km/s in the upper 400 m of the crust. [Formula: see text] increases from 30 in the upper 50 m to 150 at 500 m depth. The underlying material has a [Formula: see text] of 400–500 for the out‐cropping igneous rocks such as granite and may reach values higher than 700 for the metamorphic green schist rock. A band‐pass filtered Dirac delta source time function produces the synthetic that is the best fit with observations.