Abstract
The site amplifications for three stations, Libin (LIBI), Baisha (BASH) and Yulong (YULG) situated respectively in the southern, middle and northern parts of Lijiang Valley, are obtained by analyzing the S-wave soil/bedrock and microtremor horizontal/vertical spectral ratios. The data are digital recordings for the aftershocks of the Lijiang M s=7.0 earthquake on February 3, 1996. In the frequency range of 1–4 Hz, the S-wave soil/bedrock spectral ratio of E-W component for LIBI is the largest and amounts to 4.5. The microtremor soil N-S/vertical (V) spectral ratio is approximate to 1, E-W/V is about 4.5 and the same with above soil/bedrock spectral ratio. It is shown that the vertical and N-S components of microtremor have not been amplified by the soil and the Nakamura’s method is applicable. With this method, the microtremor spectral ratios for BASH and YULG are further evaluated. They have similar characteristics with that of LIBI. In above frequency range, both N-S/V ratios are approximate to 1, while the E-W/V ratio is about 6 for BASH, 4.5 for YULG. Lijiang Valley is characterized by the trans-valley directional site response.
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This research belongs to the “Ninth-Five Subject” (95-04-05-02-02) of China Seismological Bureau.
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Li, BJ., Qin, JZ., Luo, DH. et al. Site amplification in the Lijiang Valley, Yunnan Province. Acta Seimol. Sin. 12, 193–198 (1999). https://doi.org/10.1007/s11589-999-0024-3
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DOI: https://doi.org/10.1007/s11589-999-0024-3