Joint inversion of receiver function and surface wave dispersion observations

We implement a method to invert jointly teleseismic P-wave receiver functions and surface wave group and phase velocities for a mutually consistent estimate of earth structure. Receiver functions are primarily sensitive to shear wave velocity contrasts and vertical traveltimes, and surface wave dispersion measurements are sensitive to vertical shear wave velocity averages. Their combination may bridge resolution gaps associated with each individual data set. We formulate a linearized shear velocity inversion that is solved using a damped least-squares scheme that incorporates a priori smoothness constraints for velocities in adjacent layers. The data sets are equalized for the number of data points and physical units in the inversion process. The combination of information produces a relatively simple model with a minimal number of sharp velocity contrasts. We illustrate the approach using noise-free and realistic noise simulations and conclude with an inversion of observations from the Saudi Arabian Shield. Inversion results for station SODA, located in the Arabian Shield, include a crust with a sharp gradient near the surface (shear velocity changing from 1.8 to 3.5 km s^-1 in 3 km) underlain by a 5-km-thick layer with a shear velocity of 3.5 km s^-1 and a 27-km-thick layer with a shear velocity of 3.8 km s^-1, and an upper mantle with an average shear velocity of 4.7 km s^-1. The crust-mantle transition has a significant gradient, with velocity values varying from 3.8 to 4.7 km s^-1 between 35 and 40 km depth. Our results are compatible with independent inversions for crustal structure using refraction data.