基于数值实验的速度模型不确定性对震源参数波形反演影响研究

doi:10.12196/j.issn.1000-3274.2024.04.009

地震 ›› 2024, Vol. 44 ›› Issue (4): 131-152.doi: 10.12196/j.issn.1000-3274.2024.04.009

基于数值实验的速度模型不确定性对震源参数波形反演影响研究

郭雪琦¹, 王易², 何骁慧³, 罗艳¹, 郑凯月⁴

1.中国地震局地震预测研究所地震预测重点实验室, 北京 100036;
2.中国科学院精密测量科学与技术创新研究院, 大地测量与地球动力学国家重点实验室, 武汉 430077;
3.中山大学地球科学与工程学院, 广东省地球动力作用与地质灾害重点实验室, 珠海 519082;
4.北京大学地球与空间科学学院, 北京 100871

收稿日期:2024-05-06 修回日期:2024-06-17 出版日期:2024-10-31 发布日期:2024-12-16
通讯作者: 罗艳, 研究员。 E-mail: luoyan.wind@gmail.com
作者简介:郭雪琦(1999-), 女, 天津人, 在读硕士研究生, 主要从事震源机制解研究。
基金资助:
中国地震局地震预测研究所基本科研业务费专项(CEAIEF20220203, CEAIEF2024030102)

Research on the Influence of Velocity Model Uncertainty on Source Parameter Waveform Inversion Based on Numerical Experiments

GUO Xue-qi¹, WANG Yi², HE Xiao-hui³, LUO Yan¹, ZHENG Kai-yue⁴

1. Institute of Earthquake Forecasting, CEA, Beijing 100036, China;
2. State Key Laboratory of Geodesy and Earth’s Dynamics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430077, China;
3. Guangdong Provincial Key Laboratory of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Zhuhai 519082, China;
4. School of Earth and Space Sciences, Peking University, Beijing 100871, China

Received:2024-05-06 Revised:2024-06-17 Online:2024-10-31 Published:2024-12-16

摘要/Abstract

摘要： 震源参数是描述地震发生主要物理过程的模型表征变量, 速度模型是真实地下结构的一种近似参数表征, 两者以强弱不同的耦合方式控制各种震相的记录波形。对大量区域地震进行波形拟合源参数反演的过往研究多基于低计算消耗的一维速度模型建模地震图, 且缺乏系统定量的速度模型差异影响震源机制解反演结果的绝对误差评估。本研究以龙门山断裂带为例, 将基于波形成像得到的高分辨率三维速度模型通过高精度三维谱元法正演合成汶川强震后212个代表性区域地震(M_S3.5~5.7)的三分量宽频带波形记录, 并基于此采用多个代表性本地一维速度模型进行震源参数CAP波形反演测试。通过对不同一维模型CAP反演得到的震源参数误差进行统计分析, 系统评估一维速度模型准确度对源参数波形反演结果精确度的影响。本文在P波(0.01~0.18 Hz) 和S波(0.03~0.10 Hz) 滤波参数下得到的四组一维速度模型CAP反演机制解都较为可靠, 与预设机制解误差Kagan角小于30°的事件数都在97%以上。但CAP反演深度误差却明显依赖于速度模型, 发现不精确的浅层结构会严重影响事件反演深度。在未知速度模型准确度的情况下, CAP反演结果的归一化互相关系数NCC可以作为准确反演源深度的关键指标。本文提出的速度模型准确度评估方法和思路可以拓展到其他复杂构造区和不同一维速度模型的震源参数波形反演研究中。

关键词: 震源参数反演, 一维速度模型, 波形拟合, 模型评价

Abstract: The source parameters characterize the main physical processes of an earthquake, while the velocity model is an approximate parameter representation of the real underground structure. Both are coupled in various ways, affecting the recording of seismic phases. In the past, when fitting the waveforms of a large number of regional earthquakes to invert for source parameters, low-computational-consumption one-dimensional velocity models were often used to model the seismic waveforms, and there was a lack of systematic and quantitative assessment of the absolute error in the source mechanism solution caused by the velocity model. This study takes the Longmenshan fault zone as an example, using a high-resolution three-dimensional velocity model obtained by wave imaging to accurately perform three-component broadband waveform synthesis for 212 representative regional earthquakes (M_S 3.5~5.7) after the Wenchuan earthquake, and based on this, multiple representative regional one-dimensional velocity models are used for source parameter CAP waveform inversion tests. By statistically analyzing the source parameters obtained from the waveform inversion of different one-dimensional models and comparing them with the representative seismic source parameters, the study systematically evaluates the impact of the accuracy of one-dimensional velocity models on the precision of the source parameter waveform inversion results. In this paper, under the filtered parameters for P-waves (0.01~0.18 Hz) and S-waves (0.03~0.10 Hz), the four sets of one-dimensional velocity model inversion mechanism solutions obtained are all quite reliable, with the number of events with an error Kagan angle less than 30° accounting for more than 97%. However, the CAP inversion depth error depends on the velocity model, and it is found that the inaccurate shallow structure will severely affect the inversion depth of the event. In the case of unknown accuracy of the velocity model, the normalized cross-correlation coefficient NCC of the seismic event can be used as a key indicator for the accurate inversion of the source depth. The velocity model accuracy assessment method and ideas proposed in this paper can be extended to the source inversion research of other complex tectonic areas and different one-dimensional velocity models.

Key words: Source parameter inversion, One-dimensional velocity model, Waveform fitting, Model evaluation

中图分类号:

P315.7

郭雪琦, 王易, 何骁慧, 罗艳, 郑凯月. 基于数值实验的速度模型不确定性对震源参数波形反演影响研究[J]. 地震, 2024, 44(4): 131-152.

GUO Xue-qi, WANG Yi, HE Xiao-hui, LUO Yan, ZHENG Kai-yue. Research on the Influence of Velocity Model Uncertainty on Source Parameter Waveform Inversion Based on Numerical Experiments[J]. EARTHQUAKE, 2024, 44(4): 131-152.

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基于数值实验的速度模型不确定性对震源参数波形反演影响研究

Research on the Influence of Velocity Model Uncertainty on Source Parameter Waveform Inversion Based on Numerical Experiments

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