Kotaro Tarumi, Kazunori Yoshizawa

Many broadband seismic stations deployed permanently and temporarily in the Australian continent have been used for various seismological investigations in and around Australia. Although two horizontal components are generally assumed to be oriented in the north and east directions, as reported by data providers, misorientations of horizontal components from the true geographic north direction cannot be avoided in practical field observations, even in the well-maintained permanent stations. In this report, we applied a polarization analysis to almost all stations in Australia to estimate the misorientations of horizontal components using long-period teleseismic P-waves. A large data set of P-wave arrival angles allows us to successfully detect probable horizontal misorientations, including significant temporal changes in some stations, which generally happened at reported timings of station maintenance and instrument replacements. However, some stations exhibit misorientations and temporal changes at unexpected timings that are unreported. Compiling the information on such time-dependent misorientations, we created a full catalog of horizontal-component orientations for both permanent and temporary stations in Australia, which are widely available for the community.