Inversion and Application of Shear Velocity Structure Near Transition Zone Discontinuities Based on Multiband Pds Amplitude

Abstract

Sharpness of the transition zone seismic discontinuities and seismic velocity jump across the discontinuities provide important constraint on water content and mineral composition near the transition zone. The velocity models were constructed with different discontinuity sharpness and velocity jump to calculate corresponding receiver functions and analyze the Pds/P amplitude ratio in multiple frequency bands. The forward modeling results show that the shear velocity contrast across the discontinuity mainly affects the amplitude of Pds/P ratio while the thickness affects both the amplitude and decaying trend versus frequency. Simultaneous inversion were proposed for the discontinuity thickness and velocity jump by using a Markov Chain Monte Carlo method. Synthetic test indicates the method can effectively constrain the thickness and velocity jump. The method was applied to collected receiver function in eastern China. Results show a relatively sharp 660 km discontinuity with a 6.1% shear velocity increase over less than 2 km depth range.

Keywords

• mantle transition zone
• receiver function
• 660 km discontinuity
• discontinuity sharpness
• monte-carlo method