Building damage concentrated in Longtoushan town during the 2014 Ms. 6.5 Ludian earthquake, Yunnan, China: examination of cause and implications based on ground motion and vulnerability analyses
- 234 Downloads
Though the 2014 Ludian Earthquake had only a moderate magnitude (Ms 6.5), high-level ground motions of almost 1g occurred at Longtoushan Town (seismic station 53LLT), which located near the intersection of a conjugate-shaped seismogenic fault. The building damages on the pluvial fan and the river terrace at Longtoushan was clearly different. In order to examine the generation of the large acceleration at 53LLT, the focal mechanisms and the rupture processes of the conjugate-shaped seismogenic fault were determined. We found that there were two continuous impulsive waves in the records of 53LLT that were generated from two different faults, the Baogunao fault and the Xiaohe fault, respectively. Site effects on the pluvial fan and the river terrace at Longtoushan Town and their relations to different building damages were examined. We found that the predominant period at the pluvial fan was about 0.25 s, close to the fundamental natural period of multi-story confined masonry buildings. Ground motions on the pluvial fan and the river terrace were simulated through convolving synthesized bedrock motions with the transfer functions, which were analyzed using the one-dimensional underground velocity structures identified from H/V spectral ratios of ambient noise. Building collapse ratios (CRs) are estimated based on the vulnerability function of the 2008 Wenchuan Earthquake and are compared with the observed values. We found that the observed building CRs on the pluvial fan are much higher than the estimated values. High-level ground shaking that is far beyond the design level was a reason for serious building damage.
Keywords2014 Ludian earthquake Seismogenic structure Site effect Underground velocity structures Building collapse ratio Aseismic capacity of buildings
China Strong Motion Network Center of the Institute of Engineering Mechanics, China Earthquake Administration is highly appreciated for providing the ground motion records of the main shock and the aftershocks of the 2014 Ludian Earthquake. We owe thanks to Prof. Jianwen Cui and his colleague, Dr. Guoliang Lin, from Earthquake Administration of Yunnan Province, China, for their help in the work of onsite investigation and ambient noise measurement. We also thank the “Science Foundation of Institute of Engineering Mechanics, China Earthquake Administration” (Grant No. 2014B08) for providing the fund support to the onsite investigation.
- Fang L, Wu J, Wang W, Lü Z, Wang C, Yang T, Zhong S (2014) Relocation of the aftershock sequence of the Ms 6.5 Ludian earthquake and its seismogenic structure. Seismol Geol 36(4):1173–1185 (in Chinese with English abstract)Google Scholar
- Irikura K. (1986) Prediction of strong acceleration motions using empirical Green’s function, Proc. 7th Japan Earthq. Eng. Symp., 1986, pp.151–156Google Scholar
- Li X, Zhang J, Xie Y, Miao Q (2014) Ludian Ms 6.5 earthquake surface damage and its relationship with structure. Seismol. Geol. 36(4):1280–1291 (in Chinese with English abstract)Google Scholar
- Wang X., K. Masaki, K. Irikura, and S. Kurahashi (2010) Building response in disastrous areas during the 2008 Wenchuan earthquakes; extraction of building response parameters using microtremor measurements, Summaries of Technical Papers of Annual Meeting 2010, Architecture Institute of Japan, 1023–1024 (in Japanese)Google Scholar
- Wang X., K. Masaki, K. Irikura, and S. Kurahashi (2012) Quantitative damage criteria of severely-damaged masonry buildings during the 2008 Wenchuan earthquake from Microtremor Records, 15th WCEE, Paper NO. 4343Google Scholar
- Xie Z, Zheng Y, Liu C, Xiong X, Li Y, Zheng X (2015) Source parameters of the 2014 Ms 6.5 Ludian earthquake sequence and their implications on the seismogenic structure. Seismol Res Lett 86(6). doi: 10.1785/0220150085
- Xu X, Xu C, Yu GH, Wu XY, Li X, Zhang JG (2015b) Primary surface ruptures of the Ludian Mw 6.2 earthquake, southeastern Tibetan plateau, China. Seismol Res Lett 86(6):1622–1635. doi: 10.1785/0220150038
- Zhang G, Lei J, Liang S, Sun C (2014a) Relocations and focal mechanism solutions of the 3 August 2014 Ludian, Yunnan Ms6.5 earthquake sequence. Chin J Geophys 59(9):3018–3027 (in Chinese with English abstract)Google Scholar