ORIGINAL ARTICLE 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 Xin Wang & Susumu Kurahashi & Hao Wu & Hongjun Si & Qiang Ma & Ji Dang & Dongwang Tao & Jiwei Feng & Kojiro Irikura Received: 20 September 2016 /Accepted: 17 March 2017 # Springer Science+Business Media Dordrecht 2017 Abstract 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 inter- section 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 exam- ine 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 iden- tified from H/V spectral ratios of ambient noise. Build- ing collapse ratios (CRs) are estimated based on the vulnerability function of the 2008 Wenchuan Earth- quake 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. Keywords 2014 Ludian earthquake . Seismogenic structure . Site effect . Underground velocity structures . Building collapse ratio . Aseismic capacity of buildings 1 Introduction An earthquake struck Ludian County, Yunnan, China at 08:30:10.2 UTC (16:30:10.2 local time) on 3 August J Seismol DOI 10.1007/s10950-017-9659-z X. Wang (*) International Research Institute of Disaster Science, Tohoku University, Aoba-yama 468-1, Aoba-ku, Sendai 980-0845, Japan e-mail: wang@irides.tohoku.ac.jp S. Kurahashi Aichi Institute of Technology, Yachigusa 1247, Yagusa, Toyota, Japan H. Wu : K. Irikura Disaster Prevention Research Center, Aichi Institute of Technology, Yachigusa 1247, Yagusa, Toyota, Japan H. Si Earthquake Research Institute, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, Japan Q. Ma : D. Tao : J. Feng Institute of Engineering Mechanics, China Earthquake Administration, 29 Xuefu Road, Harbin, China J. Dang Saitama University, 255 Shimo Ohkubo Sakura-Ku, Saitama City, Japan