Joint inversion of receiver functions and surface waves for crustal structure beneath station TBZ (Trabzon)

SUMMARY Joint Inversion of Receiver Functions and Surface Waves for Crustal Structure Beneath Station TBZ (Trabzon) The current study is designed to invert shear-wave velocity structure beneath the seismic station TBZ (Trabzon). For this purpose both receiver functions and surface waves recorded at station TBZ are employed. Receiver functions are obtained from the deconvolution of three-component tele-seismic P waves, and frequently encounter multiple-solution problem when inverted alone. A joint inversion of both receiver functions and surface waves has recently been suggested to eliminate the multiple-solution, and is applied here efficiently. The new method provides a system of equations weighted properly for both data sets. This study is interesting to use all single-station data (both receiver function and surface wave) that is not frequently seen in the literature. It is better if receiver functions and surface waves sample a relatively similar velocity structure when used together. If the crustal thickness both from receiver functions and surface waves is different as much as ±10 km, the user of the method should be extra cautious against a possible misinterpretation such as experienced here. In this case, it is possible that the depth to the Moho discontinuity is estimated correctly, but not the corresponding absolute velocity thereon. One should then adjust the surface wave solution as much as necessary. The addition of relevant surface wave information to the inversion of receiver function is also effective to alleviate possible disturbances from Geological irregularities beneath the station. The crustal thickness beneath station TBZ is estimated to be 30 ±2 km to the east of the station, and 36 ±2 km to the west. Shallow shear- wave velocities are extremely low (i.e. 2.45 ±0.18 km/s). Upper crustal shear-wave velocities are estimated to be around 3.77 ±0.18 km/s (high-velocity-zone), and those in mid-crustal levels, around 3.55 ±0.18 km/s (low-velocity-zone). The velocity jump at Moho is relatively low (i.e. < 0.5 km/s), and the upper mantle Sn velocity is estimated to be 4.41 ±0.18 km/s. Key Words: Receiver Function, Multiple-solution, Crustal Velocity Structure, Inversion, Surface Wave