下記のとおり地震研究所談話会を開催いたします。

対面での開催を再開しておりますので、地震研究所へお越しいただければ幸いです。

なお、お知らせするZoom URLの二次配布はご遠慮ください。また、著作権の問題が

ありますので、配信される映像・音声の録画、録音を固く禁じます。

 　　　　　　　　　　　　　　　記

　　　　　　　　　日　　時：　令和8年4月17日(金)　午後1時30分～

　　　　　　　　　場　　所：　地震研究所1号館2階　セミナー室

　　　　　　　　　　　　　　　Zoom Webinarにて同時配信　

1. 13:30-13:45

演題：傾斜変動から推定した新燃岳で2018年に発生したブルカノ式噴火における火山灰放出源の深度と噴火発生場の考察（続報）【所長紹介（受入教員：川口 允孝）】

著者：○及川 純（日本大学）、前田裕太（名古屋大学）、田島靖久（日本工営(株)中央研究所）

2. 13:45-14:00

演題：単一欠陥 Olami-Feder-Christensen モデルにおける相境界と desynchronization: 地震のべき乗則の理解に向けて【成果発表補助 成果報告】

著者：○大谷哲人・亀　伸樹

要旨：理論的に明らかになった地震の離散モデルにおける相転移のメカニズムについて報告する。

(論文: https://doi.org/10.1103/7c3x-j5xf)

3. 14:00-14:15

演題：Fast and robust bootstrap法を用いたMT応答関数の標準誤差推定

著者：○臼井嘉哉・上嶋 誠・橋本 匡・増田正孝・秋山峻寛、坂中伸也（秋田大学）、市來雅啓・海田俊輝（東北大学）、山谷祐介（産業技術総合研究所）、小川康雄（東京科学大学、東北大学）

要旨：Fast and robust bootstrap法というロバスト推定量のためのノンパラメトリック法をMT応答関数の誤差推定に適用し、その有効性を確認した

○発表者

※時間は質問時間を含みます。

※既に継続参加をお申し出いただいている方は、当日zoom URLを自動送信いたします。

※談話会のお知らせが不要な方は下記までご連絡ください。

〒113－0032　東京都文京区弥生1－1－1　

東京大学地震研究所 共同利用担当

E-mail：k-kyodoriyo(at)eri.u-tokyo.ac.jp

※次回の談話会は令和8年5月22日(金)　午後１時30分～です。

Title:

New insights into the earthquake factory

 

Abstract:
Large, shallow earthquakes occurring on continental faults are often the most destructive, causing thousands of casualties worldwide each year. Strikingly, these earthquakes are also among the most informative for researchers seeking to advance our understanding of earthquake processes. In this presentation, I will discuss three new lessons learned from analyzing satellite radar and seismic data, as well as models of recent devastating earthquakes in Myanmar and Türkiye. These lessons touch on critical topics such as seismic gaps, off-fault damage and post-earthquake recovery. In all three cases, the findings have major implications for how we view earthquake cycles and assess seismic hazards. I will conclude by discussing these implications and exploring potential solutions.

タイトル：

Electrical Resistivity Structure of Fluid and Magma Supply Systems in Subduction Zones: A Comparison between Kyushu–KPR and the North Island, New Zealand

 

要旨：

In subduction zones, fluids transported into the Earth’s interior by subducting oceanic plates play a fundamental role in driving both magmatic and seismic activity. These fluids are released through dehydration reactions within the slab under specific pressure–temperature conditions and promote partial melting in the mantle, thereby generating magma supply systems for arc volcanism. Consequently, volcanic chains in island arcs generally develop along depth contours of the subducting slab. However, some arcs, including Kyushu in Japan and the North Island of New Zealand, contain non-volcanic segments of approximately 100 km length along the volcanic front, and the mechanisms responsible for such spatial discontinuities remain poorly understood.

To investigate the relationship between subsurface heterogeneity and arc segmentation, we compare three-dimensional resistivity structures in Kyushu and the North Island of New Zealand. In Kyushu, analyses using various electromagnetic datasets reveal crustal low-resistivity anomalies that are focused beneath individual active volcanic centers. At depths near the crust–mantle boundary, pronounced low-resistivity zones are observed beneath volcanic segments in both northern and southern Kyushu, whereas no clear anomalies are detected beneath non-volcanic segments. At depths exceeding approximately 100 km, a distinct conductive region is observed only beneath the southern volcanic segment, indicating strong spatial heterogeneity in both magmatic activity and the contribution of slab-derived fluids.

In the North Island of New Zealand, long-period magnetotelluric observations were conducted across a ~300 km × 150 km transitional region spanning the southern Taupo Volcanic Zone and adjacent non-volcanic segments along the Hikurangi subduction system. Three-dimensional resistivity modeling is underway based on preliminary one-dimensional results to better resolve structural differences between volcanic and non-volcanic segments. In the crust, a prominent low-resistivity zone is observed around the Taupo Volcanic Zone, suggesting an active thermal and fluid system. In the mantle beneath volcanic segments, a structure potentially corresponding to the oceanic slab–mantle boundary is inferred, although it is less clearly resolved compared to Kyushu. In addition, resistivity contrasts near the crust–mantle transition zone appear to correlate with the distribution of slow earthquakes and slip behavior.

These results suggest that spatial variations in slab-derived fluid distribution control both the presence or absence of arc volcanism and the segmentation of volcanic arcs, and further imply that such fluid distributions impose important constraints on seismic processes in subduction zones.

タイトル：

マントル対流・プレート運動のトロイダル成分とその周辺

要旨：

プレートのすれ違いや斜め沈み込み、リソスフェア全体のアセノスフェアに対する回転など、地球のマントル対流とその地表表現としてのプレート運動を特徴づける現象は、いずれも水平方向の物性不均質に起因する運動のトロイダル成分に由来する。この観点から、地球のプレート運動とその特徴について議論する。また、フィリピン海スラブの形状とそこから推定されるダイナミクスについても議論する（岩森・松山, 2010, 地震学会要旨; Matsuyama, 2016, PhD Thesis; Matsuyama and Iwamori, 2016,EPS)。