Analysis of Influence Characteristics of Site Ground Motion in Ya'an Area, Sichuan
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摘要: 为分析雅安地区场地结构引起的震动特性，选取该地区重大安评项目中的实际测试钻孔进行场地地震反应分析，采用等效线性化方法，并以NGA强震记录为输入，开展场地反应计算，在全面分析该地区场地地震特征的基础上，以峰值速度为参数指标，研究场地条件引起的峰值速度放大效应。研究结果表明，雅安地区场地卓越周期约为0.2 s，自振周期为0.2 s的建筑结构破坏相对严重；随着基岩峰值加速度的增大，峰值速度呈增大趋势，峰值速度与峰值加速度变化趋势并非完全一致，分析场地效应时应考虑多种地震动参数的变化规律；不同地震输入下峰值速度放大系数为1～1.8；峰值速度放大系数kv在不同强度基岩输入下，大致呈随等效剪切波速的增大而减小的趋势，软土场地更易引起场地峰值速度的放大，这种现象在芦山地震中较为明显。Abstract: In order to analyze the vibration characteristics caused by the site structure in the Ya'an area, the actual test boreholes in the major safety assessment projects in the area were selected for site seismic response analysis, The equivalent linearization method was used to carry out the site response calculation with the NGA strong earthquake records as the input. On the basis of a comprehensive analysis of the seismic characteristics of the site in this area, the peak velocity was used as the parameter index to study the magnification effect of the peak velocity caused by the site conditions. The main research results are as follows: The predominant period of the site in the Ya'an area is around the range of 0.2 s, and the building structure damage will be relatively severe if the natural vibration period is in this range; With the increase of the peak acceleration of the bedrock, the peak velocity shows an increasing trend, However, the changes in the peak velocity and the peak acceleration are not all consistent, so the variation laws of various ground motion parameters should be considered when analyzing the site effect.;The peak velocity magnification factor is between 1 and 1.5 under different seismic inputs; The site coefficient kv generally decreases with the increase of the equivalent shear wave velocity and soft soil filed is more likely to cause amplification of the peak velocity, especially in Lushan earthquake.
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图 1 雅安及周边芦山县地形地貌
Figure 1. Topographic and geomorphological map of Ya'an and surrounding Lushan
图 5 场地地表峰值加速度分布（芦山地震输入）
Figure 5. Site ground peak acceleration distribution（Lushan earthquake）
图 7 场地地表峰值速度分布（芦山地震输入）
Figure 7. Site ground peak velocity distribution（Lushan earthquake）
图 9 场地地表峰值速度放大系数分布（芦山地震输入）
Figure 9. Site ground peak velocity magnification factor distribution
图 10 场地地表峰值速度放大系数分布（NGA地震输入）
Figure 10. Site ground peak velocity magnification factor distribution
11 场地峰值速度放大系数随场地特征变化情况
11. Site ground peak velocity magnification factor varies with site characteristics
表 1 场地钻孔资料分布情况
Table 1. Site borehole data distribution map
参数分布 等效剪切波速 ${V}_{\mathrm{s}\mathrm{e} }$分布/m·s−1 覆盖层厚度 $ {d}_{\mathrm{s}\mathrm{e}} $分布/m 200～250 250～300 300～350 350～400 400～450 10～15 15～20 20～25 25～30 30～35 钻孔数/个 2 2 9 10 4 4 4 7 9 3 
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表 2 输入基岩时程信息（芦山地震强震数据）
Table 2. Input bedrock time-histories information（Data from Lushan earthquake）
地震名称 台站名称 记录编号（简称） 震级/级 震源距离/km PGA/Gal PGV/cm·s−1 芦山7.0级地震 51 TQL 051 TQL130420080202(TQL-0202) 7.0 13 280.7 12.62 51 PJD 051 PJD130420080201(PJD-0201) 7.0 13 153.6 9.87 51 LDG 051 LDG130420080202(LDG-0202) 7.0 13 86.8 5.73 51 HYT 051 HYT130420080201(HYT-0201) 7.0 13 70.7 4.39 51 MNC 051 MNC130420080202(MNC-0202) 7.0 13 25.3 1.39 51 PXZ 051 PXZ130420080202(PXZ-0202) 7.0 13 12.3 1.71
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表 3 输入基岩时程信息（NGA强震数据）
Table 3. Input bedrock time-histories information（Data from NGA）
地震名称 台站名称 记录编号 震级/级 震源距离/km PGA/Gal PGV/cm·s−1 Northridge-01 LA - Griffith Park Observatory 0994 6.69 17.5 283.4 26.51 Northridge-01 Vasquez Rocks Park 1091 6.69 17.5 148.0 18.39 Northridge-01 Lake Hughes #4 - Camp Mend 1021 6.69 17.5 82.4 6.17 Loma Prieta Point Bonita 0789 6.93 17.48 71.0 12.86 Chi-Chi, Taiwan-04 TTN042 2929 6.20 18 25.1 1.63 Chi-Chi, Taiwan-06 ILA063 3390 6.30 16 12.2 0.96
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