Abstract
Observed ground-motion intensity for six earthquakes of Mw = 6.0–6.2 that occurred in China’s North–South Seismic Zone (NSSZ) was compared with predicted medians from the BSSA14 model. The resulting between-event (δBe) and within-event (δWes) residuals for peak ground acceleration and pseudo-spectral acceleration up to 5.0 s were used to investigate the impact of source effects and path propagation on the regional variability in observed ground-motion amplitude within the NSSZ. Although the magnitude and fault type were similar among the six earthquakes, the results showed that their source effects were significantly different, which contributed in part to the regional variability in observed ground-motion amplitude. Estimated values for stress drop were found to mirror the trend in variation of the δBe values for short-period ground motions in the six earthquakes. This suggests that stress drop is an important factor for accurate representation of source effects and should be considered in the functional form of ground-motion prediction equations. Anelastic attenuation of ground motion was found to be considerably different in local areas of the NSSZ, which may constitute the primary reason for the regional variability in the observed ground-motion amplitude. The variation in δWes values confirmed that regional adjustment of anelastic attenuation in the BSSA14 model is applicable to some local areas (i.e., around the Longmenshan fault) but not to the NSSZ in its entirety.
Highlights
The North–South Seismic Zone (NSSZ) is widely recognized as one of the most seismically active zones in China
This study investigated the regional variability in ground-motion amplitude revealed in six Mw * 6.0 earthquakes that occurred within China’s NSSZ: the 2013 Mw 6.0 Minxian earthquake, 2014 Mw 6.2 Ludian earthquake, 2014 Mw 6.1 Jinggu earthquake, 2014 Mw 6.1 Kangding earthquake, and two aftershocks of the 2008 Mw 7.9 Wenchuan earthquake
Strongmotion recordings collected in these earthquakes were used, and the observed peak ground acceleration (PGA) and pseudo-spectral acceleration (PSA) were compared with the predicted medians provided by the BSSA14 model
Summary
The North–South Seismic Zone (NSSZ) is widely recognized as one of the most seismically active zones in China. The objective of this study was to investigate the regional variability in earthquake ground-motion amplitude observed following the occurrence of six earthquakes of Mw = 6.0–6.2 within the NSSZ (i.e., the Ludian, Jinggu, Kangding, and Minxian earthquakes and two aftershocks in the 2008 Wenchuan earthquake sequence). To pursue this objective, this work is divided into two parts. The between-event and within-event residuals for each earthquake were calculated and compared to investigate source and propagation path variability within the study region
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