今週のうなぎセミナーについてお知らせいたします。

Here is information of the Unagi-seminar(January, 15th).

************** Seminar on Seismology IV B, D /地震学ゼミナールIV B, D (Unagi Seminar) **************

科目：地震学ゼミナールIV B, D / Seminar on Seismology IV B, D（修士・博士）
日時：2026年 1月 15日 (木) 13:30~
場所：京都大学 防災研究所 本館E-232D

Date and Time：2026-01-15(Thursday), 13:30~
Place：Uji Campus Main Building E232D

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Speaker 1（発表者）:　辻村　祐里（TSUJIMURA Yuri）
Title（題目）:
Numerical simulation of island arc deformation due to steady plate subduction: Effects of along arc variation of plate configuration

Abstract（要旨）:
Subduction of the oceanic plate has significant influence on crustal deformation and free-air gravity anomalies at subduction zones. As a physical mechanism for island arc deformation by plate subduction, Fukahata and Matsu’ura (2016) proposed a rotation of plate along the plate interface under gravity, for two - dimensional case. For three - dimensional cases, Mori (2020) systematically showed that when the trench axis is convex toward the island arc prominent subsidence occurs in the island arc side around the bend. He also investigated the effect of a ridge on the subjecting oceanic plate, which can be applicable to the descending Philippine Sea slab. However, only one case was computed for this setting. This study investigates in detail the effects of (i) along-arc variations in plate boundary geometry and (ii) subduction direction. The aiming to achieve a physical understanding of island arc deformation mechanisms and to clarify the origin of large-scale topographic evolution.
This presentation reports current progress as a preparatory step toward the above purpose.

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Speaker 2（発表者）:　桑野　治樹（KUWANO Haruki）
Title（題目）:
Three-Dimensional Velocity Structure Estimation Around the Hida Mountains Using Seismic Tomography
(Initial 1D velocity structure estimation for that purpose)

Abstract（要旨）:
The area around the Hida Mountains targeted in this study is known for intermittent swarm earthquakes, but the relationship between seismic activity and volcanic activity remains unclear. Understanding the seismic wave velocity structure is important for grasping the locations of these earthquakes, and in many volcanic regions, three-dimensional (3-D) seismic tomography has been conducted using various methods. The inverse problem of three-dimensional (3-D) seismic tomography is formulated as a linear approximation to a nonlinear function. Thus the solutions obtained and the reliability estimates depend on the initial reference model. Therefore, studies such as Kissling et al (1994) have demonstrated that using an optimal 1D model as the starting point for 3D velocity structure analysis yields superior velocity structure data.
In this study, we employed the velest algorithm developed by Kissling (1995) to estimate an optimal 1D model, using JMA2001 (Ueno et al., 2002) as the initial model. We then compared the results of three-dimensional velocity structure analysis when using the estimated optimal 1D model as the initial value with those when using the JMA2001 1D model as the initial value. The results showed no difference in the analysis outcomes as indicated in previous studies, suggesting that the estimated 1D model still should be improved.