Name : TAKEO,  Minoru
          Position : Professor
          Division/Center :
          Resarch Area :  Seismology
 
 
 
 

Rresearch:

       My main research interest is understanding the physical process of earthquakes and the nature of volcanic earthquakes. During last 5
       years, we have studied the details of rupture processes of the 1993 Kushiro-oki, the 1994 Sanriku, the 1995 Kobe earthquakes and
       other small earthquakes; on this basis, kinematic models representing the spatio-temporal distribution of slip have been represented
       for these earthquakes. We also determined the stress distribution and constitutive relations on the fault plane of the Kobe earthquake.
       This is a first attempt to evaluate constitutive relations for a natural earthquake. Based on a detailed spatiotemporal rupture process
       of the 1994 Sanriku earthquake, we made it clear that a difference of the seismic coupling between the oceanic and the continental
       lithospheres at the subduction zone affects the rupture process of this earthquake. The details of rupture processes of particular
       earthquake change widely, but the macroscopic characteristics represent the scaling-low for large and moderate earthquakes and the
       Gutenberg-Richter's relation in wide range of magnitude. In order to understand the physical process of earthquakes systematically,
       we need to examine the complexity of rupture processes and the scaling-low of small earthquakes. Intending this research, we extend
       the dislocation model of earthquake to cover phenomena including defects, dislocation, and disclination, and derive a general
       expression for the rotational motion of seismic waves. This study makes it clear that we can estimate the spatial variation of slip
       velocity even in the source area of small earthquakes. We also develop a new method to estimate a size of seismic source by using
       stopping phases, and succeed in obtaining sizes and fault geometry of several small earthquakes. To understand the nature of
       explosive eruption, we studied the seismic waveforms excited by explosive eruption of Sakurajima volcano, and elucidated the initial
       process of the explosive eruptions. We analyzed a long-period seismic waves accompanied with a pyroclastic flow of Unzen volcano,
       and revealed the excitation mechanism. We examined low-frequency earthquakes lying near the Moho discontinuity just beneath the
       volcanic front, too. This study makes clear the characteristic and seismicity of these events at first.

Publications:

Hiroshi Aoyama, and Minoru Takeo, Wave properties and focal mechanisms of N-type earthquakes at Asama volcano, Jounal of Volcanology and Geothermal Research, 105, 1-2, 163--182, 2000.