SKS splitting measurements with unknown horizontal orientation of the ocean bottom seismograph

Broadband ocean-bottom seismograph (OBS) detection technology has become an effective geophysical way for studying the structure and dynamics of the oceanic crust and mantle. The measurement of SKS splitting parameters has been widely used for the study of anisotropy in the upper mantle. It is necessary to know the orientation of the OBS in traditional SKS splitting measurement. However, during typical OBS deployments, sensors are settled onto the seafloor through a free-fall process, leading to unknown horizontal orientation of the OBS sensors. In this paper, according to the kinetic characteristic between fast and slow wave, we develop a novel method for SKS splitting measurement with unknown horizontal orientation of the OBS. We test the method with the synthetic waveforms and real teleseismic data, respectively. Model tests show that the method is reliable for SKS splitting measurement. Relative to the traditional method of determining the orientation of the OBS first and then measuring the SKS splitting parameters, this method could get both of them at the same time, which reduces the accumulative errors in traditional method. Its application to the observational data indicates that the method in this paper is effective in SKS splitting measurement with higher reliability.