（a） A schematic map of coordinate system exhibiting the relationship between the geographical North direction，the North component and the back-azimuth （BAZ） of an event. $ \chi $ and θ indicate the sensor orientation and the BAZ of the event relative to the North component，respectively；（b） Example of the Rayleigh-wave polarization analysis from the station B. The blue circles represent the optimal sensor orientations determined from each event based on the maximum correlation coefficient between the vertical and the Hilbert transformed radial components. The red dash line depicts the resulting station orientation 115.1°；（c） The P-wave polarization analysis for determining orientation of station B. The blue dashed line depicts the optimal sensor orientation，which is 108°

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（a） A schematic map of coordinate system exhibiting the relationship between the geographical North direction，the North component and the back-azimuth （BAZ） of an event. $\chi$ and θ indicate the sensor orientation and the BAZ of the event relative to the North component，respectively；（b） Example of the Rayleigh-wave polarization analysis from the station B. The blue circles represent the optimal sensor orientations determined from each event based on the maximum correlation coefficient between the vertical and the Hilbert transformed radial components. The red dash line depicts the resulting station orientation 115.1°；（c） The P-wave polarization analysis for determining orientation of station B. The blue dashed line depicts the optimal sensor orientation，which is 108°