Station-orientation catalog for Australian broadband seismic stations

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 at well-maintained permanent stations. In this paper, 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 coincide with reported equipment replacements included in the EarthScope (IRIS) catalog. However, we also detected some unreported temporal changes in station orientation that may result from undocumented maintenance activities, such as sensor reorientation, which are typically not reflected in metadata. Improper corrections for orientation may affect waveform-based studies for the Earth's internal exploration, as demonstrated by teleseismic receiver function analyses, especially in the transverse component. 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 is widely available for the community.