Seismometer Orientation Measurements of Broadband Seismic Stations in the China Digital Seismograph Network

ABSTRACT The China Digital Seismograph Network, one of the largest national seismic networks, has been operating for over four decades which provides valuable seismic data for various scientific studies. Our investigation gathered a comprehensive dataset comprising 5,456,816 three-component waveforms from 3187 seismic events that took place over nine years (2014–2022). We assessed sensor orientations at 1056 broadband stations using the P-wave polarization method. Together with our calculation results, operation and maintenance log of regional networks, on-site checking, and manual inspection, we identified and addressed issues related to temporal changes of orientation, polarity reversal, and channel mislabeling. We found that ∼65.8% of seismometers (694) were well aligned with the absolute misorientation angle ≤3°, 20.8% of seismometers (220) were fairly well aligned with the absolute misorientation angle lying between 3° and 10°, 3.6% (38) of seismometers were misaligned exceeding 10°, and 9.8% of seismometers (104) showed a temporal variation in alignment. The fairly high consistency between our numerical results and gyrocompass measurements confirms the reliability of our investigation. We further compared the results of P-wave receiver functions analysis before and after sensor orientation correction. The findings indicate that sensor misorientation angles may lead to inaccurate and unstable seismological results. Therefore, conducting a systematic assessment, diagnosis, and correction for sensor orientation would be beneficial for advancing seismological analysis by promoting consistency, efficiency, accuracy, collaboration, reproducibility, and adaptability in data processing and interpretation.