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This paper analyzed the strong motion characteristics based on 86 three-component strong motion records of the MW 6.6 Luding earthquake. Additionally, the factors that influence the variation in ground motion for three earthquakes with similar magnitude in Sichuan Province were investigated. The analysis result indicates a strong correlation between the observed ground motion parameters and the distribution of published Modified Mercalli Intensity. The residual analysis reveals that the spectral accelerations at periods 0.1–10.0 s are amplified to 0.0798–0.3057 times the mean level in the rupture forward direction and weakened to 0.0738–0.2831 times the mean level in the rupture backward direction. The maximum pulse direction recorded by the 51LDJ station is N6°E, aligning with the vertical fault direction. The velocity pulses has distinct bidirectional pulses in the waveforms, with a PGV of 37.0 cm/s. The source effect of the strike-slip MW 6.6 Luding and MW 6.5 Jiuzhaigou earthquakes on ground motion is relatively less significant compared to the average level of mainshocks in southwest China. However, the thrust-fault MW 6.7 Lushan earthquake exhibits a stronger source effect on ground motion during short and medium periods, but a weaker source effect during long periods when compared to the average level. The anelastic attenuation of the Longmenshan, Xianshuihe, and Huya fault zones in Sichuan exhibits significant regional variation and periodic correlation. This phenomenon is closely linked to the regional tectonic background variations and the heterogeneity of crustal structure within the area. [ABSTRACT FROM AUTHOR]

We compare and analyze the consistency of observed acceleration and velocity data recorded by accelerometer and seismometer simultaneously in five aspects: time series, 5% damped response spectra, the variation and distribution characteristics of peak value ratios and spectral acceleration ratios, and correlation analysis. The results show that these two have good consistency, especially in medium-frequency bands and medium- and far-fields. In the research dataset of ground motion prediction equations (GMPEs), we propose the weight ratios of the observed acceleration and velocity records and verify that the empirical weighted ratios are reasonable and reliable and applicable to southwest China. [ABSTRACT FROM AUTHOR]

In this paper, we collect and process free-field strong motion recordings from 70 earthquakes for 4.2 ≤ M W ≤ 7.9 at 0 < R rup < 300 km between 2008 and 2018 in the active tectonic regions of southwest China, and then establish a dataset containing 1324 average horizontal ground motion (ROTD50) and corresponding metadata such as parameters of the earthquake source, distance, and site. A new ground motion prediction equation (GMPE) for the average horizontal component of peak ground acceleration (PGA), peak ground velocity (PGV), and 5% damped acceleration response spectra at periods ranging from 0.033 to 8.0 s (SA (T = 0.033–8.0 s)) is introduced. This GMPE considers multiple influencing factors such as magnitude and distance saturation effect, geometric attenuation, style-of-faulting, hanging-wall effect, linear/nonlinear site response, and anelastic attenuation. The residual evaluation and median ground motion are presented. The predicted ground motions using the new GMPE are compared with predictions from the GMPE in western China and five NGA-West2 GMPEs, and the observed ground motions of strong earthquakes which occurred in southwest China. The results show that the proposed GMPE can better reflect the influence of the earthquake source characteristic, propagation media, site effect on the ground motion attenuation characteristic in southwest China, and works well versus independent strong motion data of earthquakes in southwest China, and well reflects the general feature of ground motions for the Wenchuan and Lushan earthquakes that is rich at short-period and weak at long-period. The new GMPE shows outstanding performance estimating the horizontal ground motion of the earthquakes in southwest China for M W 4.2–7.9 (related to style-of-faulting) and R rup = 10–200 km, at sites with V S30 = 140–1130 m/s. • A new GMPE considering multiple influencing factors in southwest China is presented. • Our GMPE can reflects the hanging-wall effect of the reverse and normal faulting. • Our GMPE can reflects captures the nonlinear mean effect of soil. • Our GMPE works well versus independent strong motion data in southwest China. [ABSTRACT FROM AUTHOR]