Field survey around strong motion stations and its implications on the seismic intensity in the Lushan earthquake on April 20, 2013

The <i<M</i<<sub<s</sub<7.0 Lushan earthquake on April 20, 2013 is another destructive event in China since the <i<M</i<<sub<s</sub<8.0 Wenchuan earthquake in 2008 and <i<M</i<<sub<s</sub<7.1 Yushu earthquake in 2010. A large number of strong motion recordings were accumulated by the National Strong Motion Observation Network System of China. The maximum peak ground acceleration (PGA) at Station 51BXD in Baoxing Country is recorded as -1, 005.3 cm/s<sup<2</sup<, which is even larger than the maximum one in the Wenchuan earthquake. A field survey around three typical strong motion stations confirms that the earthquake damage is consistent with the issued map of macroseismic intensity. For the oscillation period 0.3–1.0 s which is the common natural period range of the Chinese civil building, a comparison shows that the observed response spectrums are considerably smaller than the designed values in the Chinese code and this could be one of the reasons that the macroseismic intensity is lower than what we expected despite the high amplitude of PGAs. The Housner spectral intensities from 16 stations are also basically correlated with their macroseismic intensities, and the empirical distribution of spectral intensities from Lushan and Wenchuan Earthquakes under the Chinese scale is almost identical with those under the European scale.