Orientations of Broadband Stations of the KOERI Seismic Network (Turkey) from Two Independent Methods: P- and Rayleigh-Wave Polarization

Abstract

The correct orientation of seismic sensors is critical for studies such as full moment tensor inversion, receiver function analysis, and shear-wave splitting. Therefore, the orientation of horizontal components needs to be checked and verified systematically. This study relies on two different waveform-based approaches, to assess the sensor orientations of the broadband network of the Kandilli Observatory and Earthquake Research Institute (KOERI). The network is an important backbone for seismological research in the Eastern Mediterranean Region and provides a comprehensive seismic data set for the North Anatolian fault. In recent years, this region became a worldwide field laboratory for continental transform faults. A systematic survey of the sensor orientations of the entire network, as presented here, facilitates related seismic studies. We apply two independent orientation tests, based on the polarization of P waves and Rayleigh waves to 123 broadband seismic stations, covering a period of 15 yr (2004–2018). For 114 stations, we obtain stable results with both methods. Approximately, 80% of the results agree with each other within 10°. Both methods indicate that about 40% of the stations are misoriented by more than 10°. Among these, 20 stations are misoriented by more than 20°. We observe temporal changes of sensor orientation that coincide with maintenance work or instrument replacement. We provide time-dependent sensor misorientation correction values for the KOERI network in the supplemental material.

The Influence of the North Anatolian Fault and a Fragmenting Slab Architecture on Upper Mantle Seismic Anisotropy in the Eastern Mediterranean

“…While many of these stations have been used in previous shear-wave splitting studies (Figure 2b; Biryol et al, 2010;Confal et al, 2016;Evangelidis et al, 2011;Hatzfeld et al, 2001;Kaviani et al, 2011Kaviani et al, , 2013Lemnifi et al, 2017;Olive et al, 2014;Paul et al, 2014;Sandvol et al, 2003;Yolsal-Çevikbilen, 2014), we re-analyze all data to ensure a consistent approach and, for long-running, permanent stations, to extend the temporal coverage of constraints. Additionally, a recent analysis of KOERI seismic stations (network KO in Figure 2b), measuring polarizations of P waves and Rayleigh waves (Büyükakpınar et al, 2021), shows that many of the permanent stations in Turkey included in our analysis are, or have been at some stage, misaligned. For all stations with a misalignment estimate of   5 , we have corrected horizontal component azimuths prior to analysis.…”

Constraints on the Lithospheric Kinematics in the Aegean and Western Anatolia Unveiled by SKS Splitting Observations

“…Similarly, Büyükakpınar et al. (2021) estimated relatively insignificant sensor misorientation (as 7.6° ± 1.3) at the station AYDB as 7.6° ± 1.3 through P ‐wave polarization analysis performed on 84 events. The details of the method used for polarization analysis are given in Supporting Information S1 (Figure S5 in Supporting Information S1).…”

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

“…There are several methods that can constrain sensor misorientation from seismic waveform records. Previous studies used the body wave polarization measurement (Shin et al, 2009;Niu and Li, 2011;Lee and Sheen, 2015;Scholz et al, 2017;Wang et al, 2016;Ensing and van Wijk, 2018;Ojo et al, 2019;Braunmiller et al, 2020;Xu et al, 2020;Zhu et al, 2020;Büyükakpınar et al, 2021;Zeng et al, 2020), surface wave polarization measurement (Stachnik et al, 2012;Rueda and Mezcua, 2015;Scholz et al, 2017;Doran and Laske, 2017;Ojo et al, 2019;Xu et al, 2020;Zhu et al, 2020;Büyükakpınar et al, 2021), comparative analysis of observed and synthetic waveforms (Ekström and Busby, 2008;Ekström and Nettles, 2018;Braunmiller et al, 2020), ambient noise crosscorrelation (Zha et al, 2013;Lee and Rhie, 2015;Xu et al, 2018;Ensing and van Wijk, 2018;Zeng et al, 2020), and receiver function analysis (Lim et al, 2018;Zheng et al, 2020). In this study, we explored two methods based on P-wave polarization for estimating the misorientation of seismometers considering computational efficiency and relative ease in implementation for rapid assessment of the station quality.…”