Measurement of seismometer misorientation based on P-wave polarization: application to permanent seismic network in South Korea

摘要

Reliable information on the horizontal orientation of a seismometer is crucial to seismological research utilizing three-component seismograms. In this study, we provide misorientation angles of broadband seismometers in three permanent networks in South Korea from 2003 to 2021 by using two methods, denoted as P-PCA and P-minT, both utilizing P-wave polarization characteristics. Our estimates show that 36% of the sensors have been aligned within 5 degrees from the geographic north during their operation periods, while 40% of the sensors have been rotated by more than 10 degrees at least once. The estimates are highly consistent for both methods, with 95% of the total showing uncertainty less than 10 degrees. Moreover, we identified a significant number of temporal changes in misorientation by taking automatic change point detection and visual inspection. The procedure described here and misorientation angles can be useful reference for seismic data preprocessing for research utilizing horizontal-component seismograms for earthquake sciences.