Development of a High-Gain Rotational-Motion Seismograph

高增益旋转地震仪的研制

• 批准号: 11640407
• 负责人: TAKEO Minoru
• 金额: $ 1.79万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2001
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640407/
• 关键词: Rupture process; Small earthquakes

We propose a method to obtain source parameters, most importantly the rupture velocity, of small earthquakes based on stopping phases. It is assumed that a rupture begins at one focus of an ellipse and spreads radially at a constant rupture velocity on the fault surface, eventually terminating on the elliptical boundary. This model allows us to investigate a wide variety of rupture configurations, ranging from a circular to a unilaterally propagating rupture. In this model, we find that two high-frequency stopping phases, being Hilbert transformations of each other, are radiated and that the difference in arrival times between the two stopping phases is dependent on the average value of the rupture velocity, the radius of the major semi-axes of the ellipse, and its ellipticity. These parameters can be estimated by a nonlinear least-squares inversion method. We perform simulation tests, which allow us to detect a Hilbert transform pair whose arrival times coincide with ones predicted by an assumed source model from noisy data. These simulation tests show that our inversion method is useful. Since our method does not require an a priori assumption of the average rupture velocity, the orientation of the fault plane, and the circular crack model, it provides us with a tool for estimating accurate source dimensions as well as rupture processes of small earthquakes.

我们提出了一种基于停止阶段的小地震的源参数（最重要的是破裂速度）的方法。假定破裂从椭圆的一个焦点开始，并在断层表面的恒定破裂速度下径向扩散，最终终止于椭圆形边界上。该模型使我们能够研究各种破裂构型，从圆形到单方面繁殖的破裂。在该模型中，我们发现两个高频停止阶段是彼此的希尔伯特变换，并且是辐射的，并且两个停止阶段之间的到达时间差异取决于破裂速度的平均值，这是Ellipse的主要半轴的半径及其椭圆度及其椭圆度。这些参数可以通过非线性最小二乘反转方法估算。我们执行仿真测试，使我们能够检测一个希尔伯特变换对，其到达时间与噪音数据中假定的源模型预测的时代相吻合。这些仿真测试表明我们的反转方法很有用。由于我们的方法不需要先验假设平均破裂速度，断层平面的方向和圆形裂纹模型，因此它为我们提供了一种工具，用于估算准确的源尺寸以及小地震的破裂过程。

项目成果

Kazutoshi Imanishi and Minoru Takeo: "Estimates of fault dimensions for small earthquakes"Geophy.Res.Lett.. 25,15. 2897-2900 (1998)

Kazutoshi Imanishi 和 Minoru Takeo：“小地震断层尺寸的估计”Geophy.Res.Lett.. 25,15。

Imanishi, K., M.Takeo: "Estimates of fault dimensions for small earthquakes using stopping phases"Geophysical Research Letters. 25. 2897-2900 (1998)

Imanishi, K., M.Takeo：“使用停止阶段估计小地震的断层尺寸”地球物理研究快报。

Imanishi, K., and M. Takeo: "Estimates of fault dimensions for small earthquakes using stopping phases"Geophysical Research Letters. 25. 2897-2900 (1998)

Imanishi, K. 和 M. Takeo：“使用停止阶段估计小地震的断层尺寸”地球物理研究快报。

Imanishi, K., M.Takeo: "An Inversion method to analyze rupture processes of small earthquakes"Journal of Geophysical Research. 107. (2002)

Imanishi, K., M.Takeo：“一种分析小地震破裂过程的反演方法”地球物理研究杂志。

Kazutoshi Imanishi and Minoru Takeo: "An inversion method to analyze rupture process of small earthquske"J. Geophy. Res.. (2000)

今西一俊、武雄稔：“分析小地震破裂过程的反演方法”J.