Analysis of strong ground motion characteristics in the near-field for the June 1, 2022 M_s6. 1 Lushan earthquake and comparison with the GMPE in southwest China

Based on 61 three-component strong motion acceleration records of the M(s)6. 1 Lushan earthquake, we analyzed the characteristics of near-field strong ground motion amplitude, and spatial distribution of horizontal ground motion intensity. Then we compared spectral accelerations (SAs) observed in the near-field stations with the median predictions of the NGA-West2 and ZYLW22 ground motion prediction equations (GMPEs). To test whether the M(s)6.1 Lushan earthquake conforms to the ground motion attenuation characteristics of the main shock in southwest China, we compared the observed values to the median predictions of the ZYLW22 GMPEs, as well as analyzed the distribution of the within-event residuals. The results show that: (1) the ground motion intensity recorded by some near-field stations is much smaller than the corresponding ground motion intensity of the seismic intensity delineated by the China Earthquake Administration. (2) The spatial distribution shows that the SAs observed in the rupture forward (north-east of the epicenter) are larger than those in the rupture backward at the same distance, especially in the long period; The short-period SAs observed in the rupture forward are greater than the median predictions of NGA-West2 and ZYLW22 GMPEs, while the SAs observed in the rupture backward are almost the same as the median predictions of ZYLW22 GMPEs throughout the period, showing a relatively significant directivity effect. (3) The ZYLW22 GMPE can well predict most horizontal ground motion of the M(s)6. 1 Lushan earthquake. The ground motion attenuation rates are different between the active tectonic regime and the stable tectonic regime. The GMPE study in southwest China should be carried out in the tectonic active regime and the stable regime, respectively, and the influence of the directivity effect and basin effect should be considered in the GMPE.