ABSTRACT

Strong‐motion recordings observed during the Ms 7.0 Jiuzhaigou earthquake, which occurred on 8 August 2017 in western China, were used to reveal the underlying source, propagation path, and site effects in comparison with observations from the 2013 Lushan earthquake of identical magnitude (Ms 7.0). The similar VS30 distributions at the strong‐motion stations considered in both events reflect approximately consistent site effects. Amplitudes of short‐ and intermediate‐period ground motions (e.g., peak ground accelerations, peak ground velocities, and pseudospectral accelerations [PSAs] at T=0.2 and 2.0 s) observed in the Jiuzhaigou event were smaller than in the Lushan earthquake at sites with a Joyner–Boore distance (RJB) of <200  km, but their amplitudes were similar at far‐field sites (RJB>200  km). However, irrespective of RJB, larger amplitudes of long‐period ground motions (e.g., PSAs at T=5.0  s) were observed in the Jiuzhaigou earthquake compared with the Lushan event. This study revealed that different fault styles (strike slip for the Jiuzhaigou event and reverse slip for the Lushan event), and different centroid depths could be two reasons for the period‐dependent differences of ground motions between the two earthquakes. Analysis of within‐event residuals suggested that the Jiuzhaigou region exhibited slower anelastic attenuation for short‐ and intermediate‐period ground motions than the Lushan region, but the anelastic attenuations for long‐period ground motions of both regions were similar. The durations of ground motions generated by both earthquakes were found comparable, as were the dependences on distance in both seismogenic regions.

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