The use of crustal higher modes to constrain crustal structure across Central Asia

We investigate the feasibility of observing crustal higher mode surface wave dispersion and applying these observations to improve estimates of crustal structure. Because crustal overtones propagate most efficiently and are excited best in regions with thick crust and deep crustal seismicity, the study concentrates on Central and Southern Asia and parts of the Middle East. We develop a new data set of observations of the group velocities of Rayleigh and Love wave first crustal overtones between a 7- and 18-s period across this region, and present dispersion maps for the first crustal overtone between periods of 10 and 17 s. A Monte Carlo inversion of the first higher mode together with fundamental mode dispersion at several locations demonstrates that the higher modes significantly reduce the range of acceptable crustal models and improve the resolution of the crust from the mantle. General application of the method across continents worldwide is probably not feasible, as a result of the low likelihood of observing large numbers of first overtones in regions of normal continental crustal thickness devoid of deep crustal seismicity.