Refined Seismic Hazard Assessment of Fault Intersection Zones in Sichuan-Yunnan Region Based on OpenQuake
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摘要:
为评估复杂构造背景下现有地震动区划图在活跃断裂带地震风险评估中的适用性，提升地震危险性分析的准确性.以2022年川滇地区Ms6.8级泸定地震影响区为研究对象，基于OpenQuake平台开展概率地震危险性分析（PSHA）.研究通过地震目录处理、震级转换、震源参数估算和断层建模，构建包含背景地震源与断层源的区域地震模型，并选取多种适用于活跃浅层地壳构造的地面运动预测方程（GMPEs），生成地震动参数和超越概率分布图.结果表明，OpenQuake模拟地震动分布与中国第五代地震动区划图基本吻合，尤其在高峰值加速度（PGA）区域表征上更为准确.随着峰值加速度（PGA）阈值的提高，高超越概率区域逐渐缩小，并集中于主要断层附近.以0.1为震级档，避免了五代图在地震矩释放率上的低估问题.此外，还表明强震风险主要集中在断层交汇地带，建议将该区域作为重点监测与防护对象.
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关键词:
- 危险性分析 /
- OpenQuake /
- 川滇地区 /
- 截断型古登堡-里克特关系 /
- 工程地质学
Abstract:This study aims to evaluate the applicability of existing seismic ground motion zoning maps in earthquake risk assessment for active fault zones under complex tectonic settings and improve the accuracy of seismic hazard analysis. Focusing on the affected area of the 2022 Ms 6.8 Luding earthquake in the Sichuan-Yunnan region, probabilistic seismic hazard analysis (PSHA) was conducted using the OpenQuake platform. Through seismic catalog processing, magnitude conversion, source parameter estimation, and fault modeling, a regional seismic model incorporating both background seismic sources and fault sources was established. Multiple ground motion prediction equations (GMPEs) suitable for active shallow crustal tectonics were selected to generate seismic motion parameter distribution maps and exceedance probability analysis results. The findings demonstrate that OpenQuake-simulated ground motion distributions align fundamentally with China's fifth-generation seismic ground motion zoning map, particularly showing enhanced accuracy in identifying high peak ground acceleration (PGA) zones. As PGA thresholds increase, high-exceedance probability areas gradually diminish and concentrate near major faults. By adopting 0.1 magnitude increments, this research avoids the underestimation of seismic moment release rates observed in the fifth-generation zoning map. Furthermore, results indicate concentrated strong earthquake risks in fault intersection zones, suggesting these areas should be prioritized for monitoring and protective measures.
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图 1 研究区域地形及断层分布
标点处为2022年泸定Mw6.8地震，断层线的引用数据来源于中国地震灾害防御中心地震活动断层探察数据中心（
https://www.activefault-datacenter.cn ）Fig. 1. Topography and fault distribution of the study area
图 2 研究区域地震分布情况及机制
a.研究区域的主要活动断裂带与其地震深度震级分布图，黄色线为活动断裂；b.研究区域部分地震的震源机制图，沙滩球为1976—2024年Ms4.7以上地震震源机制解（
www.globecmt.org ）Fig. 2. Seismic distribution and mechanisms in the study area
图 3 OpenQuake情景地震模拟下的泸定地震PGA分布
Fig. 3. PGA distribution of Luding earthquake under OpenQuake scenario seismic simulation
图 4 地震目录去聚类及完整性验证
a.研究区域主要地震事件的震级-时间分布图，蓝色点为主震，红色点余震；b.研究区域主要地震事件随时间和震级的分布图，中间的红线代表地震完整性分析的边界，用于区分地震目录中数据的完整性和不完整性部分
Fig. 4. Earthquake catalog declustering and completeness verification
图 5 研究区域最大震级与地震震级-频次关系计算
a.川滇地区地震最大震级估算的累积地震矩曲线图，其中红色实线为实际累积地震矩，蓝色实线为预测累积地震矩，虚线为上下界，箭头指示最大震级估算值（Mw=7.609）；b.川滇地区地震发生率模型与观测数据对比图，其中蓝色点为观测增量发生率，蓝色实线为模型增量发生率；红色方块为观测累积发生率，红色实线为模型累积发生率
Fig. 5. Maximum magnitude and magnitude-frequency distribution in the study area
图 6 平滑背景地震源的归一化地震发生率等高线
图中的左右两个颜色条分别是年份与平滑背景地震源的平滑率.左颜色条表示地震发生的时间，由蓝色到黄色表示年份依次递增；右颜色调表示地震发生概率的空间分布强度，从紫色到黄色依次渐强
Fig. 6. Normalized seismic rate contours for smoothed background seismic sources
图 7 研究区域的OpenQuake的模拟结果的PGA分布图与中国第五代地震图对比
XSH-F.鲜水河断裂带；XJH-F.小金河断裂带；XJ-F.小江断裂带；JSJ-F.金沙江断裂带；LMS-F.龙门山断裂带；EY-JB-F.峨阳-金边断裂带
Fig. 7. Comparison of OpenQuake-simulated PGA distributions with China's fifth-generation seismic zonation map in the study area
图 8 不同抗震烈度等级下研究区域50 a内地震动超越概率的空间分布
a. 抗震烈度等级为7级，PGA=0.10 g；b. 抗震烈度等级为7级，PGA=0.15 g；c. 抗震烈度等级为8级，PGA=0.20 g；d. 抗震烈度等级为8级，PGA=0.30 g
Fig. 8. Spatial distribution of seismic motion exceedance probabilities within 50 a under different seismic intensity levels in the study area
表 1 震源深度概率质量函数(PMF) 分布
Table 1. Probability mass function (PMF) distribution of hypocenter depth
深度(km) 2.5 7.5 12.5 17.5 22.5 27.5 概率 0.279 0.046 0.384 0.228 0.050 0.013 
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