Joint inversion of high frequency surface waves with fundamental and higher modes

The six-layer earth model (Xia et al., 1999) is used to analysis sensitivity of surface wave multi-modes to the shear velocities and depth of each layer. Results show that fundamental mode is more sensitive to the parameters of shallow layers and concentrated on a very narrow band while higher modes is more sensitive to the parameters of relatively deeper layers and distributed over a wider frequency band. These properties present the condition of joint inversion. Inversion of both synthetic data and real-world example demonstrate that joint inversion of high frequency surface waves with fundamental and higher modes applying damped least mean square method with SVD technique to inverse shear velocities can effectively reduce the ambiguity, and improve the stability and precision of inversion. The inversion results can be farther improved if a proper higher mode is chosen to joint inversion with fundamental mode.