摘要:
新疆地区地震活动频繁，地质条件复杂，局部场地条件对地震产生的强地面运动和工程震害有重要影响。本文基于区域剪切波速分布和场地分类资料，研究了新疆地区场地覆盖土层对区域地震危险性的影响。使用中国第五代地震动参数区划图中的潜在震源三级划分方法和Bindi等提出的区域地震动衰减模型，基于新疆地区场地剪切波速分布和场地分类，给出了新疆地区基岩Ⅰ1类场地（VS30=742 m/s）和实际场地的50年超越概率63%、10%和2%的地震动峰值加速度（PGA）及周期为0.2 s、0.5 s和1 s的反应谱加速度（Sa）的危险性结果。根据地震危险性分析结果考察了不同超越概率下新疆地区Ⅱ类和Ⅲ类场地相对于Ⅰ1类场地的地震危险性差异，统计得到土层场地的不同概率水平的地震动参数调整系数。结果表明：受场地覆盖土层影响，PGA以及0.2 s、0.5 s和1 s的反应谱加速度在塔里木和准噶尔盆地等土层较软地区有明显放大作用，而在阿尔泰山、天山和昆仑山脉等硬岩地区，相同概率水平的地震动参数有明显的降低。Ⅱ类和Ⅲ类场地反应谱加速度调整系数，在不同周期的调整系数相差较大，呈现出随周期的增大先增大再减小的规律，在周期为0.4 s时调整系数为最大，显示出场地影响在不同周期的显著差异；对于不同超越概率水平，II、III类场地的地震动调整系数几乎相同，这表明场地调整系数受区域地震危险性水平的影响较小。与五代图的平均调整系数相比，新疆地区I1类场地的调整系数偏小，而Ⅲ类场地的调整系数则偏大。本研究对于抗震设防考虑区域场地条件的影响具有参考价值。
Abstract:
The Xinjiang region is characterized by frequent seismic activity and complex geological conditions, where local site conditions significantly influence strong ground motions and engineering seismic damage. This study investigates the impact of site overlying soil layers on regional seismic hazard in Xinjiang, based on regional shear-wave velocity distribution and site classification data. Using the potential seismic source zoning method from the fifth-generation seismic zonation map of China and the regional ground motion attenuation model proposed by Bindi et al., seismic hazard results—including peak ground acceleration (PGA) and spectral accelerations (Sa) at periods of 0.2 s, 0.5 s, and 1.0 s—were calculated for bedrock Site Class I1 (VS30 = 742 m/s) and actual sites under 50-year exceedance probabilities of 63%, 10%, and 2%. The differences in seismic hazard between Site Class II/III and Site Class I1 in Xinjiang were analyzed across varying exceedance probabilities. Adjustment coefficients for ground motion parameters at different probability levels were statistically derived for soil sites. The results indicate that influenced by site overlying soil layers, the PGA and response spectral accelerations at 0.2 s, 0.5 s, and 1.0 s exhibit significant amplification in soft soil regions such as the Tarim and Junggar Basins, while ground motion parameters at the same probability level are notably reduced in hard-rock areas like the Altai, Tianshan, and Kunlun Mountains. For Site Class II and III, the adjustment factors for response spectral accelerations vary significantly across different periods, showing a pattern of first increasing and then decreasing with increasing period. The adjustment factors reach their maximum at a period of 0.4 s, highlighting the substantial differences in site effects across spectral periods. For different exceedance probability levels, the adjustment factors for Site Class II and III are nearly identical, suggesting minimal influence of regional seismic hazard levels on site-specific adjustments. Compared to the average adjustment factors in the fifth-generation seismic zonation map, the adjustment factors for Site Class I1 in Xinjiang are smaller, while those for Site Class III are larger. This study provides valuable insights for seismic fortification by considering the impact of regional site conditions.
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