| The Lushan MS7.0earthquake occurred on April20,2013, at Lushan country,Sichuan province, which is another devastating earthquake following the2008Wenchuan earthquake and the2010Yushu earthquake in China in recent years. We gothigh-quality near-field earthquake observation data in Lushan earthquake, whichproviding valuable database for our study on Lushan strong earthquake ground motioncharacteristics. There are some similarities between Lushan and Wenchuan earthquakein epicenter location and source characteristics, but Lushan earthquake revealed thatthe seismic damage would be slight for the larger PGA. By studying the properties ofstrong motion in the Lushan earthquake, we can get a better understanding of thestrong motion characteristics in the southwestern of China mainland. Based on thenear-field strong motion records in the Lushan earthquake and taking sufficientconsideration of source mechanics and seismic damage, this article analyses theparameters and characteristics of strong motion in the Lushan earthquake and the detailwork is below.1. Based on the records from Wenchuan earthquake and Japan, we developedlogarithmic linear regression equation between PGA and other parameters. Consideringthe magnitude, epicentral distance and site, we found there have no effect on theregression analysis about the PGA and other parameters except individual parameters.By comparing the Lushan data with regression equation obtained from above, wefound Lushan earthquake in line regression equation.2. Based on the records obtained from42stations with fault distance less than200km from Lushan earthquake, records have been compared with the NGA and fittedusing the simplified attenuation model. We reveal the NGA model underestimated andoverestimated the Lushan earthquake for the short period and long period respectively,through comparing the residual of the spectral acceleration between the observedrecords in Lushan earthquake and the prediction by NGA.3. Near-fault hanging-wall and foot-wall records classified by the sourcemechanics in Lushan earthquake were studied. The hanging wall effect was found inLushan earthquake after the residual of simplified attenuation model and the NGAspectral acceleration attenuation curves.4. Comparing the PGA and Housner intensity with the values computed usingcode spectra, the truth that PGA is far over the values computed using code spectra for design earthquake and close to the values computed using code spectra for rareearthquake while the Housner intensity below the values computed using code spectrafor design earthquake explains the seismic damage was slight for the larger PGA inLushan earthquake. |
