近日，武汉大学Chuanyi Zou团队研究了2011年东北地震长周期自由振荡的激发：数值实验和震源参数的影响。2025年5月6日出版的《大地测量与地球动力学》杂志发表了这项成果。

长周期自由振荡为大地震的时空特征提供了可靠的信息。在这项研究中，课题组采用正模求和算法在非球面、滞弹性和旋转地球模型中生成三分量地震图，重点研究2011年东北大逆冲地震对地震正模的激发。具体而言，他们分析了震源参数的影响，包括断层几何形状、震源深度和破裂持续时间。通过将合成自由振荡谱与观测数据进行比较，验证了几种震源机制，并强调了水平观测对改进地震机制反演的必要性。 

该定量分析表明，在断层几何参数中，倾角和滑动角对激发振幅的影响比断层走向更为明显。某些故障配置增强了特定模式的可检测性，强调了故障几何形状和模式激励之间的关系。正常模式对焦深也表现出不同的敏感性，在不连续边界处激发振幅变化显著。此外，研究组证明，虽然可以通过最小化观测光谱和合成光谱之间的差异来推断破裂持续时间，但应该包括更广泛的记录和模式。

附：英文原文

Title: Excitation of long-period free oscillations by the 2011 Tohoku earthquake: numerical experiments and influence of source parameters

Author: Chuanyi Zou

Issue&Volume: 2025/05/06

Abstract: Long-period free oscillations provide robust information for the spatio-temporal characteristics of large earthquakes. In this study, we employ a normal-mode summation algorithm to generate three-component seismograms within an aspherical, anelastic, and rotating Earth model, focusing on the excitation of seismic normal modes by the 2011 Tohoku megathrust earthquake. Specifically, we analyze the effects of seismic source parameters, including fault geometry, focal depth, and rupture duration. By comparing synthetic free oscillation spectra with observed data, we validate several source mechanisms and emphasize the need for horizontal observations to improve seismic mechanism inversions. Our quantitative analyses reveal that among fault geometry parameters, dip and slip angles have a more pronounced impact on excitation amplitudes than fault strikes. Certain fault configurations enhance the detectability of specific modes, underscoring the relationship between fault geometry and mode excitation. Normal modes also exhibit varying sensitivity to focal depth, with significant excitation amplitude changes at discontinuity boundaries. Additionally, we demonstrate that while rupture duration can be inferred by minimizing differences between observed and synthetic spectra, more extensive records and modes should be included.

DOI: 10.1016/j.geog.2025.04.001

Source: https://www.sciencedirect.com/science/article/pii/S1674984725000370