Joint Inversion of Surface Wave Dispersions and Receiver Functions with P Velocity Constraints: Application to Southeastern Tibet

Abstract We introduced a P velocity model into the traditional joint inversion of P receiver function (RF) and surface wave dispersions to reduce model ambiguity. The method was implemented using a global search‐based algorithm and a flexible parameterization of a sedimentary layer and spline‐based parameterization that can represent sharp discontinuities. We applied the method to a dense array in SE Tibet (longitude ~97.5°E to 107°E, latitude ~25.3°N). Extensive tests using synthetic and real data suggest that the method is suitable and robust for a variety of velocity structures and Moho discontinuities and can simultaneously provide the crustal V p / V s profile and better constrained Moho depth. The flexibility of the parameterization and the inclusion of the V p constraint are crucial in the improved model recovery. Artifacts may be created without including the sedimentary layer. Even when it is less perfect, a reasonable V p model is valuable in such a joint inversion. We showed that crustal multiples in RFs may bias the traditional H ‐ k results when the crust structure is complex and should be avoided in a joint inversion before appropriate corrections can be made. The results from the joint inversion show two low‐velocity zones (LVZs) reported previously and were identified as channels of crustal flow. A prominent isolated LVZ is observed in the mid‐lower crust under the Xiaojiang fault area, which correlates with anomalously high V p / V s ratios, indicating possible partial melting. However, the other LVZ is imaged to be in the brittle shallow upper crust without very high V p / V s ratios, which is likely associated with crustal fault zones rather than partial melting. We observe clear low‐velocity structures in the mantle beneath the two crustal LVZs, which also correlate with zones of low resistivity. The crust‐mantle correlation may suggest influence of mantle processes on crustal deformation.