We introduce a novel method to determine the azimuthal orientation of borehole seis-mometer using microseisms that are ubiquitously present in seismic records. The micro-seisms are dominantly composed of Rayleigh waves that construct plane wavefronts over local stations. We determine the borehole seismometer orientation by comparing the polarization directions of Rayleigh waves in microseisms between borehole and surface stations. The Rayleigh wave polarization directions are determined using the nature of Rayleigh wave ground motions that present a 90° phase difference between the radial and vertical components. The azimuthal differences in apparent Rayleigh wave polarization directions between borehole seismometer and local surface seismometer provide information on the misorientation angle of borehole seismometer. Both the primary and secondary microseisms can be used. The method is applied to determine the misorientation angles of two deep borehole seismometers in the Yonsei Earth Observatory in Seoul, South Korea. The misorientation angles of borehole seismometers are determined stably using 18-hour-long ambient noise records, suggesting instant determination of borehole seismometer orientation based on short-time ambient noise records. Regional-event seismic waveforms at borehole seismometers match well with those at collocated surface station, supporting the correct determination of borehole seismometer orienta-tion. The proposed method does not require information on seismic source locations and ray paths unlike conventional methods, allowing prompt determination of borehole seismometer orientation with high precision.
|Number of pages||17|
|Journal||Bulletin of the Seismological Society of America|
|Publication status||Published - 2022 Oct|
Bibliographical noteFunding Information:
The authors are grateful to Stefano Parolai (Associate Editor) and two anonymous reviewers for constructive review comments. The seismic records were collected from Korea Meteorological Administration (KMA). This work was supported by the Korea Meteorological
The authors are grateful to Stefano Parolai (Associate Editor) and two anonymous reviewers for constructive review comments. The seismic records were collected from Korea Meteorological Administration (KMA). This work was supported by the Korea Meteorological Administration Research and Development Program under Grant Number KMI2022-00710. In addition, this research was partly supported by National Research Foundation of Korea (NRF-2017R1A6A1A07015374).
© Seismological Society of America.
All Science Journal Classification (ASJC) codes
- Geochemistry and Petrology