Interseismic stress accumulation at the locked zone of Nankai Trough seismogenic fault off Kii Peninsula

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doi: 10.1016/j.tecto.2013.03.015
Author(s): Kinoshita, Masataka; Tobin, Harold J.
Author Affiliation(s): Primary:
Japan Agency for Marine-Earth Science and Technology, Kochi Core Center, Kochi, Japan
University of Wisconsin at Madison, United States
Volume Title: Great earthquakes along subduction zones
Volume Author(s): Kimura, Daku, editor; Brodsky, Emily; Di Toro, Giulio; Ide, Satoshi; Kanagawa, Kyuichi; Park, Jin-Oh; Underwood, Michael
Source: Great earthquakes along subduction zones, edited by Daku Kimura, Emily Brodsky, Giulio Di Toro, Satoshi Ide, Kyuichi Kanagawa, Jin-Oh Park and Michael Underwood. Tectonophysics, Vol.600, p.153-164. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0040-1951 CODEN: TCTOAM
Note: In English. 45 refs.; illus., incl. 1 table, sketch map
Summary: A primary source of stress variation prior to great subduction zone earthquakes is the tectonic loading due to plate convergence. We have calculated the elastic stress around the locked zone accumulated during an interseismic period numerically, using a 2D plane-strain finite element model in the Nankai Trough off Kii Peninsula, and examined its dependence on elastic properties and some boundary conditions. For the modeling, we used the geometry of subducting plate interface determined previously through seismic surveys and the physical properties that were obtained through IODP scientific drilling offshore Kii Peninsula. To construct a physically realistic model, a dislocation along the plate interface is calculated from a 5 m displacement imposed on one side of the subducting plate, with the locked zone defined at a depth of 10 to 25 km along the plate interface. Calculated shear stress is maximized at the downdip edge of the locked zone, decreases exponentially seaward, and is almost zero near the updip edge. Maximum shear stress is primarily proportional to the Young's modulus of the overlying section. Comparing the maximum shear stress with the average stress drop for subduction earthquakes (3-4 MPa), the most appropriate Young's modulus and Poisson's ratio ranges are 50-70 GPa and ∼0.3, respectively, which are in good agreement with previous estimations from observed Vp/Vs. The stress accumulated during one seismic cycle can be reasonably explained by a linear elastic model with an appropriately sized locked region. We found that the envelope of simulated horizontal displacement on the surface agrees well with GPS velocity data, which also supports this inference. Disturbance near the updip edge is no larger than 0.1 MPa of stress or ∼0.1µ-radian of tilt, which are difficult to detect with current borehole measurement techniques and likely complex borehole conditions. Abstract Copyright (2013) Elsevier, B.V.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 16 Structural Geology; 19 Geophysics, Seismology; Active faults; Asia; Body waves; Earthquakes; Elastic constants; Elastic waves; Far East; Faults; Finite element analysis; Finite strain analysis; Geometry; Global Positioning System; Honshu; Integrated Ocean Drilling Program; Japan; Kii Peninsula; Models; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; P-waves; Pacific Ocean; Plate convergence; Plate tectonics; S-waves; Seismic waves; Seismicity; Shear stress; Stress fields; Subduction; Subduction zones; Velocity; West Pacific; Young's modulus
Coordinates: N330000 N350000 E1380000 E1360000
Record ID: 2014001335
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands