In this division, we are investigating the mechanism of phenomena related to earthquakes and volcanism on a global scale based on theoretical, observational, and experimental studies, including data analyses and laboratory works.

Field of Global Tectonics

The aim of this field is to reveal origins of various types of tectonics on the Earth's surface from the viewpoint of the global dynamics of the Earth's interior. Particularly, the circulation of the water and its role on tectonics and earthquake generation is investigated. The following themes are currently studied: (1) Plate motions around the Japanese islands, (2) stresses within plates and slabs, (3) driving forces of plates, (4) mechanisms of interplate, intraslab, and intraplate earthquakes, and (5) serpentinization of the mantle wedge and its implication to tectonics.

Low-frequency tremors (Obara, 2002) do not occur where island-arc crust is subducting, where no intraslab earthquakes occur within the subducting crust. If the dehydration embrittlement is a cause for intraslab earthquakes, it means that there is no or less dehydration in the subducting crust in such places. They are also the places where interplate earthquakes are less active.

Field of Geodynamics

In this field, we try to understand the mantle dynamics and its surface manifestation through various modelings. The studies include the numerical simulation of the mantle convcection and subduction zones.

Three-dimensional distribution of temperature (left) and temperature anomalies (right)

Field of Theoretical Volcanology Research

In this field, we study volcanological phenomena and other phenomena related to dynamics of magma from the viewpoint of fluid dynamics. Our recent results are as follows. (1) A model to explain transition from non-explosive to explosive volcanic eruption, (2) an analytical model of conduit flow during explosive eruption to specify magma discharge rate as a function of geological and magmatic parameters, (3) a numerical model of the dynamics of eruption column and pyroclastic flow, and (4) a model of the heat and mass transfer and differentiation of magma in magma chambers.

Field of Experimental Magmatology

;In this field, the studies on the magmatic evolutions and physical conditions of magmas are going at active volcanoes such as Mt. Fuji, Miyakejima and Mt. Asama volcanoes. Melt inclusions are powerful tool to investigate the pre-eruptive volatile content of magma which controls the eruptive style.

Melt inclusion

Field of Geochemistry

In this field, we investigate material transfer in subduction zone including phenomena related to volcanic activity and time scale of the transfer using Multicollector-ICP-MS (IsoProbe, Micromasss) and Laser Ablation ICP-MS. We use isotopic tracers such as Li and Hf for the studies on material transfer and radio active disequilibrium of daughter nuclides of 238U, such as 230Th and 226Ra for putting time constraints on the material transfer.

A plasma ion source

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