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Structural Seismology Group

Structural Seismology Group

photo Structural Seismology Group
Group Leader
Seiichi MIURA

  • Research on structures of seismogenic zones along plate boundaries
  • Research on seismological structures, seismic activities and alteration of oceanic plates
  • Research on large-scale subseafloor structure and subseafloor structure with high resolution
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Structural Seismology Group

To reveal the mechanisms of ocean floor dynamics and generation processes of great earthquakes and tsunamis, it is necessary to understand the structures and properties below the seafloor. As a technique to extensively study the conditions beneath the seafloor that we cannot directly see, seismic surveys have been widely performed. The sub-seafloor structure can be inferred by analyzing seismic waves (sound waves) generated by controlledsources on a research vessel and recorded by a multichannel seismic streamer (refl ection method) and ocean-bottom seismographs (refraction method). The Structural Seismology Group conducts seismic surveys in wide range of fields including subduction zones where great megathrust earthquakes occur, such as the Nankai Trough and the Japan Trench, oceanic plates where outer-rise earthquakes occur, and back-arc regions where active faults are densely distributed, such as the eastern margin of the Japan Sea. Together with structural analyses and numerical modelling, we aim to clarify the structures below the seafloor in these seismogenic/tsunamigenic zones. In recent years, numerical simulation on earthquake and tsunami generation and off shore drilling studies using deep-sea drilling vessel Chikyu, have been increasingly conducted, and it is required to capture the sub-seafloor structure with higher resolution and accuracy. For this reason, we cooperate with researchers and engineers in a variety of fi elds and try to develop new survey technologies and analysis tools.


figure1
A bird’s-eye view (from north) of the Philippine Sea plate subducting beneath the Eurasian plate around the source region of Tonankai earthquake. Color represents the depth of the plates.
figure2
The streamer cable for multi-channel seismic reflection survey. Near the sea surface, a number of receivers (hydrophones) record seismic waves reflected from boundaries below the seafloor.
figure3
Ocean-bottom seismographs for refraction survey, which record seismic waves refracted/reflected from the sub-seafloor.