中国科学院地质与地球物理研究所王新及其团队成员最新的研究，对中国西南地区三维地壳地震速度模型的性能、局限性和前景方面进行了评估。这一研究成果发表在2024年1月22日出版的国际学术期刊《中国科学：地球科学》上。

在本研究中，研究人员使用区域三维波形模拟，以评估各种区域地壳三维速度模型在再现观测地震记录方面的性能。研究过程中，特别关注该地区最近发生的两次地震序列，即2021年云南漾濞M_S6.4地震序列和2022年四川泸定M_S6.8地震序列。测试的三维速度模型包括中国西南地区社区速度模型V1.0、中国大陆岩石圈统一地震层析成像模型V2.0、青藏高原东部地壳和上地幔伴随全波形层析成像模型以及中国大陆浅层地震构造模型。研究结果表明，测试的3D速度模型通常可以很好地捕获长周期(＜0.2 Hz)波形，表明3D模型足以解析整体大尺度的地下结构。

然而，三维合成材料在较高频率(0.05-0.3 Hz)上存在差异，并且三维速度模型的性能因区域而异，这表明较小尺度的非均质性没有得到很好的约限制。包括浅层速度结构(<10km)可以改善波形拟合，强调了在波形建模中纳入浅层结构的重要性。全波形层析成像模型表现出比其他模型稍好的性能，特别是对于体波，虽使用了很长周期的波形，结果还是突出了全波形方法在实现亚波长分辨率方面的优势。根据这些模型性能的比较结果，研究人员确定了不同地震层析成像模型和方法的优点和局限性，并提出了结合不同的层析成像方法和数据集来更好地约束地下结构的建议。研究结果强调，尽管本项研究的目标是中国西南地区，但研究所进行的分析可以应用于其他不同规模和构造背景的地区进行定量地震模型评价。

据了解，中国西南地区是一个构造和地震活跃的地区，由于印度板块和欧亚板块的碰撞，这里发生了强烈的形变。因此，限制该区域的地下速度结构，对理解大陆碰撞的构造和地球动力学过程以及减轻地震灾害具有重要意义。此前，大量的研究提供了西南地区不同的三维地震速度模型。然而，这些模型之间存在差异，并且对这些现有速度模型的可靠性和准确性进行量化的尝试较少。

附：英文原文

Title: Evaluation of 3D crustal seismic velocity models in southwest China: Model performance, limitation, and prospects

Author: Xin WANG, Ling CHEN, Qi-Fu CHEN

Issue&Volume: 2024-01-22

Abstract: Southwest China is a tectonically and seismically active region, witnessing strong deformation due to the collision between the Indian and Eurasian plates. Constraining the subsurface velocity structure of this region is thus important in understanding the tectonics and geodynamic processes of continental collision and in mitigating seismic hazards. Numerous studies have provided various 3D seismic velocity models in southwest China. However, discrepancies exist among these models, and less effort has been made to quantify the reliability and accuracy of these existing velocity models. In this study, we use regional 3D waveform simulation to evaluate the performance of various regional crustal 3D velocity models in reproducing observed seismograms. We particularly focus on two recent earthquake sequence in the region, the 2021 Yunnan Yangbi M_S6.4 earthquake sequence and the 2022 Sichuan Luding M_S6.8 earthquake sequence. The tested 3D velocity models include the Southwest China Community Velocity model V1.0, the Unified Seismic Tomography Models for Continental China Lithosphere V2.0, the adjoint full waveform tomography model of the crustal and upper mantle beneath Eastern Tibetan Plateau, and the shallow seismic structure model beneath continental China. Our results show that the tested 3D velocity models generally capture well long-period (<0.2Hz) waveforms, indicating that the 3D models adequately resolve overall large-scale subsurface structures. However, the 3D synthetics show discrepancies in higher frequencies (0.05–0.3Hz) and the performance of the 3D velocity models varies from region to region, suggesting that smaller scale heterogeneities are not well constrained. Including shallow velocity structures (<10km) can improve the waveform fitting, emphasizing the importance of incorporating shallow structures in waveform modeling. The full-waveform tomography model shows a slighter better performance than the other models, especially for the body-waves, highlighting the advantages of full-waveform method in achieving sub-wavelength resolution despite the usage of very long-period waveforms. In light of these comparison results of model performance, we identify the advantages and limitations of different seismic tomography models and methods, and we propose to incorporate different tomography methods and datasets to better constrain subsurface structures. While our target region in this study is southwest China, the analysis that we have conducted can be applied to other regions of various scales and tectonic settings for quantitative seismic model evaluation.

DOI: 10.1007/s11430-023-1215-1

Source: https://www.sciengine.com/10.1007/s11430-023-1215-1