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BSSA: Comparison of Strong Ground Motion Recordings of the Lushan, China, Earthquake of 20 April 2013 with the Next Generation Attenuation (NGA) West2 Ground Motion Models

2017/12/5 10:04:41

The Next Generation of Attenuation (NGA-West2) of America is the most advanced ground motion prediction model. At present, the application of this model in European countries and others has been systematic researched. However, its application on Chinese earthquakes and the problems in the application have seldom reported in China. After Lushan earthquake happened in 2013, the China Strong Motion Network Center achieved much strong motion data for this event, which provide the convenience for the comparison between the Chinese earthquake data and the NGA-WEST2 prediction value. Therefore, basing on the 39 stations with site-to-rupture distance less than 200 km (shown in Fig. 1), Yuzhu Bai, the associate researcher in China Earthquake Administration, Institute of Geology, compared the prediction value of the Lushan earthquake by NGA-WEST2 with that by strong ground motion data.

 

Figure 1. The locations of recordings applied in this study.

▲-The strong-motion station; ●- The Lushan earthquake epicenter; ★- The Wenchuan earthquake epicenter

By the comparison, the findings are followings: (1) Overall, for most Lushan station recordings over the whole range of Rrup, the spectral acceleration (Sa) of the peak ground acceleration (PGA) and of T = 0.06 s are within one standard deviation of the predictions from the five NGA West2 GMPEs. Most intra-event residuals also fall between plus and minus one standard deviation from the predictions. (2) The standard deviation of intra-event residuals are smaller for Sa of T = 0.06 s than for PGA, which suggests that the application of NGA West2 in predicting high frequency ground motion due to the Lushan earthquake is acceptable. (3) In general, the five NGA West2 GMPEs generate relatively large intra-event residuals at the long period (T = 1.0 s) for Rrup exceeding 100 km, although the intra-event residuals are not as large. (4) The short period hanging wall effects are more consistent with the NGA West2 hanging wall scaling than those of long period, and the short period ground motions on the footwall are more consistent with the NGA West2 models than those on the hanging wall. (5) The spatial contours of intra-event residuals for PGA predicted by the five NGA West 2 models are almost the same, all showing four regions of negative intra-event residuals. Three of these regions are mainly distributed with the source-to-site azimuth approximating to 90°or -90°, while the other one approximating to -180°, consistent with the extrusion and rupture directions of the Lushan earthquake fault, as shown in Fig 2.

Figure 2. Plots of intra-event residuals in space for PGA computed by the five NGA West2 GMPEs

▲-The strong-motion station; ●- The Lushan earthquake epicenter; ★- The Wenchuan earthquake epicenter

The dashed rectangle is the possible surface projection of Lushan earthquake fault

The above research achievements are published in Bulletin of the Seismological Society of America上(Yuzhu Bai. Comparison of Strong Ground Motion Recordings of the Lushan, China, Earthquake of 20 April 2013 with the Next Generation Attenuation (NGA)‐West2 Ground‐Motion Models. 2017, 107 (4): 1724-1736)

https://pubs.geoscienceworld.org/ssa/bssa/article/107/4/1724/354054/comparison-of-strong-ground-motion-recordings-of