Orientation variations of the seismometers in the Aleutian Islands and their impacts on shear wave splitting analyses

Rayleigh wave polarization analysis is adopted to calculate the seismometer orientations of 59 seismic stations in the Aleutian Islands including networks AK, AT, AV, IM, TA, and XJ. For most stations, the orientations deviate slightly from the geographical north pole while a few stations show strikingly large misorientations. The misorientations can be caused by many anthropogenic factors, such as the re-orientation after the deployment or the installation of new instruments, which leads to the variations of seismometer orientations during the station operation period. The orientations of the seismometer plays a significant role in seismology studies. For example, if the deviation of the orientation from the geographical north pole is large, it will affect the obtained values of fast orientations of splitting shear waves. Therefore the orientation of the stations need to be corrected for the seismic data by time interval.