STUDYING THE DEPTH-DEPENDENT VARIATION OF SITE MAGNIFICATION FACTOR IN DONGCHUAN BY EARTHQUAKES OBSERVED IN BOREHOLE
Luo Dihua
Jiang Lequn
Junpei Akamats
Chen Mingong
Ye Jianqing
Cai Shaoping
Liu Xuejun
Abstract：The digital seismometers with high accuracy are installed at depths of -200 m, -100 m in deep hole and on the surface in Dongchuan. By analysis of spectra ratio, the local events (with epicentral distances between 8.5 km and 95 km, magnitudes ML =1.3～5.1) recorded are used to calculate site magnification factor at different depths (-100 m and surface) in Dongchuan. Comparing results with that at the depth of -200 m, the site magnification factors at three components of N-S, E-W and U-D corresponding to the depth of -100 m at 8 frequencies ( f = 0.75, 1.0, 1.5, 2, 3, 4, 6, and 12 Hz) are 1.0～1.49 when 0.75 ＜f＜2 Hz and 0.47～0.99 when 2 ＜f＜ 12 Hz. On the surface, site magnification factors at three components are all greater than 1, i.e. between 1.6 and 7.63. The correlation coefficients of site magnification factors for S wave and coda at the depth of -100 m and on surface are 0.82 and 0.81 when 0.75 ＜f＜ 2 Hz, 0.47 and 0.45 when 2 ＜f＜12 Hz, respectively.
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Publication Date：2001-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：11( 68-78 )