Overview
The solid earth science group studies the physical and chemical state of the crust,
mantle, and
core on a variety of temporal and spatial scales. We seek a quantitative and
comprehensive view of
the Earthfs present state and the processes by which it evolved, and of the interacti
ons between
layers. Among the phenomena we study are earthquakes and volcanoes, crustal
deformation and the
evolution of surface topography, the thermal state and material transport in the
mantle, the formation,
evolution, and subduction of the oceanic crust, core dynamics and the generation of th
e Earthfs
magnetic field. To understand this complex system we use a wide variety of
approaches, including
continuum mechanics, geodynamics, theories of fracture and failure, studies of
topography,
structural geology, petrology, crystallography, geochemistry, theoretical and
experimental high
pressure-high temperature mineral physics, magneto-hydrodynamics, seismic tomography
and
waveform inversion, earthquake source theory, large scale numerical simulation,
analyses of large
datasets on a global scale, and field studies. We are studying the solid earth using
the above wide
variety of approaches and viewpoints with the goal of achieving a unified and
comprehensive
understanding of its evolution. Our group has chosen to focus on the following four
areas:
Earthquake Science (phenomena on time scales from seconds to hundreds of years
associated with
earthquake occurrence), Tectonics (in particular, phenomena on times scales from
hundreds of years
to millions of years occurring at convergent margins), Evolution of the solid Earth
(chemical and
physical phenomena on times scales from millions of years to billions of years
involved in the
formation and evolution of the Earth as a whole), and Dynamics of the Earthfs interior (the state and
structure of the Earth at present). We discuss our efforts in each of these four
areas in detail below.
@
Our Scope of Research
Earthquake Science
We conduct research on the quasi-static buildup of elastic energy and stress,
pre-seismic
acceleration of slip on faults, the occurrence of large earthquakes and radiation of
seismic waves,
after-slip, recovery processes in the fault zone, and stress redistribution due to
relaxation in the
asthenosphere. By understanding these processes on a variety of spatial and temporal
scales we will
improve our understanding of the earthquake occurrence process as a complex system
and obtain
reliable statistical models. On the basis of the above research we will evaluate the
predictability of
13 earthquakes.
Tectonics
We seek unified and quantitative understanding of subduction-related orogeny,
continental
collision, and back-arc spreading, considering the interaction between endogenetic
processes caused
by physical and chemical reactions within plate boundary zones, and exogenetic
processes (such as
erosion, transportation and deposition) that are controlled mainly by climate.
Evolution of the Solid Earth
We seek an understanding of the differentiation of materials and the formation of
the structure
of the Earthfs interior, particularly of the crust and core, and of the energetics an
d mechanisms of
material transport processes, and of the interactions between the surface and the
crust, the crust and
the mantle, and the mantle and core. Through our study of the above phenomena we
will contribute
to achieving a unified and quantified model of the thermal and chemical evolution of
the Earth from
its formation to the present.
Dynamics of the Earthfs Interior
By analyzing data on a global scale, conducting large scale numerical simulation,
and carrying
out leading-edge laboratory experiments we seek an understanding of the present
state and evolution
of the crust, upper mantle, transition zone, lower mantle, and outer and inner core.
We particularly
focus on the interactions between the various layers and on elucidating the
heterogeneous properties
of each layer, from thermodynamic, geodynamic, electromagnetic, and material science
viewpoints,
with the aim of synthesizing these analyses to obtain a unified understanding of
geodynamics.