Frictional response of accreted sediments to seismic slip propagation along subduction plate boundary faults

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Author(s): Hirose, T.; Mukoyoshi, H.; Tanikawa, W.; Lin, W.; Tadai, O.; Noda, H.
Author Affiliation(s): Primary:
Japan Agency for Marine-Earth Sciences and Technology, Nankoku, Japan
Marine Works of Japan, Japan
Volume Title: AGU 2011 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2011; American Geophysical Union 2011 fall meeting, San Francisco, CA, Dec. 5-9, 2011. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: In order to evaluate the frictional response of shallow sediments to seismic slip propagation along faults within accretionary prisms, we have conducted friction experiments on clay-rich sediments from IODP Expedition 316, Nankai Trough. Recent high-velocity friction experiments demonstrated that frictional resistance of simulated faults increases at the onset of sliding of over slip distance of more than several millimeters (the initial frictional barrier), that is followed by prolonged slip-weakening (e.g., Sone & Shimamoto, 2009). In this study special attention is paid to the initial frictional barrier at the onset of rapid sliding, because it may be a significant factor controlling earthquake rupture propagation from the depth into the shallow accretionary prisms and subsequent tsunami generation (e.g., the 2011 off the Pacific coast Tohoku earthquake). In the experiments, we slid a simulated fault gouge at a constant slip rate of 0.1 mm/s and then increase slip rate to 1.3 m/s with different acceleration of from 0.13 to 13 m/s2 under normal stresses of 0.5-2.0 MPa and water saturated conditions. We consider the applied acceleration as a proxy for acceleration at a propagating rupture front. In all runs, friction coefficient is 0.6-0.7 at slip rate of 0.1 mm/s and then increases by 2-10% over distance of several centimeters as a fault starts accelerate. Amplitude of the initial frictional barrier and hardening distance seem to depend on acceleration. When a simulated fault overcomes the initial barrier, friction coefficient gradually decreases with slip toward the steady-state value of 0.3∼0.4. In order to evaluate whether the initial barrier can affect rupture propagation, we estimate a ratio of the frictional work consumed on a fault during the initial hardening stage to the frictional work during the weakening. The ratio is about ∼0.01 at acceleration of 0.13 m/s2, but tends to increase with acceleration to ∼0.15 at 13 m/s2. The amplitude of the barrier also depends on normal stress: it decreases by ∼30% as increasing normal stress from 0.5 to 2.0 MPa. In addition, a critical slip rate threshold of dynamic slip-weakening shifts from ∼5 mm/s to ∼0.15 m/s as increasing acceleration from 0.13 to 13 m/s2. Such frictional barrier and shift of the threshold of critical slip rate are hardly recognized on the diagram showing velocity dependence of steady-state friction (e.g., Di Toro et al., 2011). Our result suggests that as the acceleration at the rupture front increases due to crack extension or rupture acceleration, the effect of initial frictional barrier at the onset of rapid faulting could become significant; large initial barrier may decelerate the rupture. The effect of initial barrier must be incorporated into the analysis of earthquake rupture propagation in subduction zones.
Year of Publication: 2011
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; Accretion; Earthquakes; Expedition 316; Faults; Friction; High-velocity zones; Integrated Ocean Drilling Program; NanTroSEIZE; Nankai Trough; North Pacific; Northwest Pacific; Pacific Ocean; Plate boundaries; Plate tectonics; Propagation; Rupture; Sediments; Simulation; Slip rates; Stress; Subduction; West Pacific
Coordinates: N330100 N331400 E1364800 E1364300
Record ID: 2015099588
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