地震地质 ›› 2024, Vol. 46 ›› Issue (5): 1091-1105.DOI: 10.3969/j.issn.0253-4967.2024.05.006

• 研究论文 • 上一篇    下一篇

面向地震动估计需求的区域传播介质参数

郑兴群1,2,3)(), 陶正如1,2),*(), 白凯1,2)   

  1. 1) 中国地震局工程力学研究所, 中国地震局地震工程与工程振动重点实验室, 哈尔滨 150080
    2) 地震灾害防治应急管理部重点实验室, 哈尔滨 150080
    3) 北京交通大学, 土木建筑工程学院, 北京 100044
  • 收稿日期:2023-07-17 修回日期:2024-02-28 出版日期:2024-10-20 发布日期:2024-11-22
  • 通讯作者: 陶正如, 女, 1978年生, 博士, 研究员, 主要从事工程地震方面的研究工作, E-mail: taozr@iem.ac.cn
  • 作者简介:

    郑兴群, 男, 1997年生, 现为北京交通大学土木工程防灾减灾专业在读博士研究生, 主要从事工程地震方面的研究工作, E-mail:

  • 基金资助:
    国家重点研发计划项目(2019YFE0115700); 国家自然科学基金(51678540)

REGIONAL PROPAGATION MEDIUM PARAMETERS FOR GROUND MOTION ESTIMATION

ZHENG Xing-qun1,2,3)(), TAO Zheng-ru1,2),*(), BAI Kai1,2)   

  1. 1) Institute of Engineering Mechanics, China Earthquake Administration; Key Laboratory of Earthquake Engineering and Engineering Vibration of China Earthquake Administration, Harbin 150080, China
    2) Key Laboratory of Earthquake Disaster Mitigation, Ministry of Emergency Management, Harbin 150080, China
    3) Beijing Jiaotong University, School of Civil Engineering and Architecture, Beijing 100044, China
  • Received:2023-07-17 Revised:2024-02-28 Online:2024-10-20 Published:2024-11-22

摘要:

地震动估计是抗震设计和风险评估的重要输入来源。地震动估计中, 地震波在地壳介质中的传播可用几何扩散项和非弹性衰减项表达。文中针对这2项区域传播介质特性, 从几何扩散项和非弹性衰减项2个角度分别开展研究。首先, 以地震记录丰富的日本东北部地区为研究区, 使用遗传算法反演几何扩散项参数并讨论震级、 震源深度及莫霍面深度的影响。结果表明: 莫霍面埋深对几何扩散项参数的影响最大。将此结果用于中国西部的四川、 新疆和云南地区, 按照莫霍面深度分区并分段拟合几何扩散项参数。在此基础上, 从地质学的角度重新划分区域, 借助遗传算法反演得到不同分区的非弹性衰减项参数Q0η等。结果表明: 在大地热流数值较高、 莫霍面较浅、 上地壳剪切波速较低、 地震活动较强烈的地区, 地震波衰减较快, 通常Q值较低; 在地质年代由古及今、 高程增加的情况下, Q值逐渐减小。面向地震动估计所需的区域地壳介质参数Q值, 给出了反演区域范围的划分方案, 即四川的东部地区和新疆天山地区为高Q值区域, 云南、 四川中西部地区和新疆喀什地区为低Q值区域。其中, 云南西北部和四川中西部为Q值相对更低的地区。

关键词: 地震动估计, 几何扩散项, 非弹性衰减项, 品质因子

Abstract:

Estimating the possible ground motion generated by future earthquakes can provide input for seismic design, which is an important research direction in engineering seismology. It is widely used in seismic risk analysis, earthquake zoning, post-earthquake emergency, earthquake disaster mitigation planning. Ground motion is estimated in two ways: first, the attenuation relation of ground motion is simplified to express the relationship between ground motion and earthquake size, focal characteristics, propagation medium and site influence; Second, the near-fault ground motion of large earthquakes is synthesized by using finite fault source model and Green’s function. Both of the two ways describe the influence of source, propagation medium and site conditions. Among them, the propagation of seismic waves in the medium can be expressed in terms of geometric spreading term and inelastic attenuation term. In this study, the characteristics of these two regional propagation media are studied from two perspectives: the geometrical spreading term and the inelastic attenuation term. Firstly, the northeastern region of Japan, with abundant seismic records, is taken as the research area, and the effects of magnitude, focal depth, and Moho depth are discussed by using a genetic algorithm. The results show that the Moho depth significantly influences the geometrical spreading parameters. The results were applied to the regions of Sichuan, Xinjiang and Yunnan in western China, and the geometric spreading terms were determined according to the depth of the Moho plane and the least square method was used to fit the geometric spreading term. On this basis, from the geological point of view, according to the geological time, earth heat flow value, surface elevation, Moho buried depth, upper crust shear wave velocity and seismic activity, the regions are re-divided, and the inelastic attenuation parameters Q0 and η are obtained by using genetic algorithm. According to the above six factors, it can be found that the stress drop is distributed in 30-130bar, κ0 in 0.025-0.06s, Q0 in 220-350, η in 0.56-0.96. Among them, the discussion of the influence of various influencing factors on the Q0 in this paper can be described as follows: When grouped according to geological time, the value of Q0 decreases from Paleozoic to Cenozoic. When divided into two groups according to geothermal conditions, the Q0 value of the low heat area is greater than that of the high heat area. When it is divided into three groups according to the elevation, which are less than 1 000m, between 1 000 and 3 000m and above 3 000m, the Q0 value decreases with the elevation increase. When the buried depth of the Moho surface is divided into deep and shallow buried areas, the Q0 value of the deep buried area is greater than that of the shallow buried area. When the shear wave velocity of the upper crust is divided into two groups, the Q0 value of the low-speed region is smaller than that of the high-speed region. When the seismic activity is divided into strong seismic activity and weak seismic activity, the Q0 value of the weak seismic activity region is greater than that of the strong seismic activity region. By analyzing the inversion results, some rules of quality factor distribution in the study area can be summarized: seismic wave attenuation is faster and Q value is usually lower in the areas with high ground heat flow, shallow Moho surface, low shear wave velocity and strong seismic activity; With the increase of geological time from ancient to present and elevation, the Q value decreases gradually. Combined with the calculated value of the regional crustal medium parameter Q, which is required for ground motion estimation, the division scheme of the inversion area is given, that is, the eastern part of Sichuan and Tianshan region of Xinjiang are the regions with high Q values, Yunnan, central and western parts of Sichuan and Kashi region of Xinjiang are the regions with low Q values, and the northwestern part of Yunnan and west and central part of Sichuan are the regions with relatively lower Q values. During the study of the inelastic attenuation term, the study area was redivided according to the influence of a single factor. In the follow-up research, the study area will be redivided according to the cross-over of different influencing factors to explore the influence of the inelastic attenuation term. At the same time, the next step will continue to improve the zoning standards in western China and draw the zoning map.

Key words: Ground motion estimation, Geometric spreading, Inelastic attenuation, Quality factor