Evolution of the Nankai Trough décollement from the trench into the seismogenic zone: Inferences from three-dimensional seismic reflection imaging

Geology ◽  
2004 ◽  
Vol 32 (4) ◽  
pp. 273 ◽  
Author(s):  
Nathan L. Bangs ◽  
Thomas H. Shipley ◽  
Sean P.S. Gulick ◽  
Gregory F. Moore ◽  
Shinichi Kuromoto ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Nankai Trough ◽  
Three Dimensional ◽  
Seismogenic Zone ◽  
Reflection Imaging

scholarly journals Dip angles of active faults from the surface to the seismogenic zone inferred from a 2D numerical analysis of visco-elasto-plastic models: a case study for the Osaka Plain

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hayami Nishiwaki ◽  
Takamoto Okudaira ◽  
Kazuhiko Ishii ◽  
Muneki Mitamura
Keyword(s):  
Urban Areas ◽  
Active Faults ◽  
Three Dimensional ◽  
Seismogenic Zone ◽  
Earthquake Ground Motion ◽  
Convex Curve ◽  
Seismic Reflection Profile ◽  
Geological Structures ◽  
Dimensional Distribution ◽  
Dip Angle

AbstractThe geometries (i.e., dip angles) of active faults from the surface to the seismogenic zone are the most important factors used to evaluate earthquake ground motion, which is crucial for seismic hazard assessments in urban areas. In Osaka, a metropolitan city in Japan, there are several active faults (e.g., the Uemachi and Ikoma faults), which are inferred from the topography, the attitude of active faults in surface trenches, the seismic reflection profile at shallow depths (less than 2 km), and the three-dimensional distribution of the Quaternary sedimentary layers. The Uemachi and Ikoma faults are N–S-striking fault systems with total lengths of 42 km and 38 km, respectively, with the former being located ~ 12 km west of the latter; however, the geometries of each of the active faults within the seismogenic zone are not clear. In this study, to examine the geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone, we analyze the development of the geological structures of sedimentary layers based on numerical simulations of a two-dimensional visco-elasto-plastic body under a horizontal compressive stress field, including preexisting high-strained weak zones (i.e., faults) and surface sedimentation processes, and evaluate the relationship between the observed geological structures of the Quaternary sediments (i.e., the Osaka Group) in the Osaka Plain and the model results. As a result, we propose geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone. When the friction coefficient of the faults is ~ 0.5, the dip angles of the Uemachi and Ikoma faults near the surface are ~ 30°–40° and the Uemachi fault has a downward convex curve at the bottom of the seismogenic zone, but does not converge to the Ikoma fault. Based on the analysis in this study, the dip angle of the Uemachi fault zone is estimated to be approximately 30°–40°, which is lower than that estimated in the previous studies. If the active fault has a low angle, the width of the fault plane is long, and thus the estimated seismic moment will be large.

scholarly journals Workshop explores seismogenic zone drilling in the Nankai trough

Eos ◽  
2001 ◽  
Vol 82 (45) ◽  
pp. 532-532
Author(s):  
A. Taira ◽  
G. Moore ◽  
H. Tobin ◽  
G. Kimura ◽  
S. Kodaira
Keyword(s):  
Nankai Trough ◽  
Seismogenic Zone

scholarly journals Preliminary results are in from mid-ocean ridge three-dimensional seismic reflection survey

Eos ◽  
1999 ◽  
Vol 80 (16) ◽  
pp. 181 ◽  
Author(s):  
S. C. Singh ◽  
M. C. Sinha ◽  
A. J. Harding ◽  
G. M. Kent ◽  
P. J. Barton ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Three Dimensional ◽  
Preliminary Results ◽  
Mid Ocean Ridge ◽  
Ocean Ridge
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