scholarly journals Dynamics of Earthquake Faulting in Subduction Zones: Inference from Pseudotachylytes and Ultracataclasites in an Ancient Accretionary Complex

2007 ◽  
Vol SpecialIssue ◽  
pp. 92-93
Author(s):  
K. Ujiie
Keyword(s):  
Subduction Zones ◽  
Accretionary Complex ◽  
Southwest Japan ◽  
Fault Rocks ◽  
Seismic Slip ◽  
Earthquake Faulting ◽  
Splay Faults

The fault rocks in ancient accretionary complexes exhumed from seismogenic depths may provide an invaluable opportunity to examine the mechanisms and mechanics of seismic slip in subduction thrusts and splay faults. In order to understand the dynamics of earthquake faulting in subduction zones, we analyzed pseudotachylytes and ultracataclasites from the Shimanto accretionary complex in southwest Japan. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.s01.21.2007" target="_blank">10.2204/iodp.sd.s01.21.2007</a>

scholarly journals Fluid pressurisation and earthquake propagation in the Hikurangi subduction zone

2021 ◽  
Author(s):  
Stefano Aretusini ◽  
Francesca Meneghini ◽  
Elena Spagnuolo ◽  
Christopher Harbord ◽  
Giulio Di Toro
Keyword(s):  
Shear Strength ◽  
Pore Pressure ◽  
Subduction Zone ◽  
Subduction Zones ◽  
Fluid Pressure ◽  
Low Permeability ◽  
Earthquake Rupture ◽  
Fault Rocks ◽  
Seismic Slip ◽  
Saturated Clay

&lt;p&gt;In subduction zones, seismic slip at shallow crustal depths can lead to the generation of tsunamis. Large slip displacements during tsunamogenic earthquakes are attributed to the low coseismic shear strength of the fluid-saturated and non-lithified clay-rich fault rocks. However, because of experimental challenges in confining these materials, the physical processes responsible of the coseismic reduction in fault shear strength are poorly understood. Using a novel experimental setup, we measured pore fluid pressure during simulated seismic slip in clay-rich materials sampled from the deep oceanic drilling of the P&amp;#257;paku thrust (Hikurangi subduction zone, New Zealand). Here we show that seismic slip is characterized by an initial decrease followed by an increase of pore pressure. The initial pore pressure decrease is indicative of dilatant behavior. The following pore pressure increase, enhanced by the low permeability of the fault, reduces the energy required to propagate earthquake rupture. We suggest that thermal and mechanical pressurisation of fluids facilitates seismic slip in the Hikurangi subduction zone, which was tsunamigenic about 70 years ago. Fluid-saturated clay-rich sediments, occurring at shallow depth in subduction zones, can promote earthquake rupture propagation and slip because of their low permeability and tendency to pressurise when sheared at seismic slip velocities.&lt;/p&gt;

Subduction zone heterogeneity observed across the magnitude spectrum for megathrust earthquakes

2021 ◽  
Author(s):  
Susan Bilek ◽  
Emily Morton
Keyword(s):  
Spatial Heterogeneity ◽  
Subduction Zone ◽  
Stress Drop ◽  
Subduction Zones ◽  
Cascadia Subduction Zone ◽  
Ocean Bottom ◽  
Small Earthquake ◽  
Megathrust Earthquakes ◽  
Seismic Slip ◽  
Subduction Zone Earthquakes

&lt;p&gt;Observations from recent great subduction zone earthquakes highlight the influence of spatial geologic heterogeneity on overall rupture characteristics, such as areas of high co-seismic slip, and resulting tsunami generation.&amp;#160; Defining the relevant spatial heterogeneity is thus important to understanding potential hazards associated with the megathrust. The more frequent, smaller magnitude earthquakes that commonly occur in subduction zones are often used to help delineate the spatial heterogeneity.&amp;#160; Here we provide an overview of several subduction zones, including Costa Rica, Mexico, and Cascadia, highlighting connections between the small earthquake source characteristics and rupture behavior of larger earthquakes.&amp;#160; Estimates of small earthquake locations and stress drop are presented in each location, utilizing data from coastal and/or ocean bottom seismic stations.&amp;#160; These seismicity characteristics are then compared with other geologic and geophysical parameters, such as upper and lower plate characteristics, geodetic locking, and asperity locations from past large earthquakes. &amp;#160;For example, in the Cascadia subduction zone, we find clusters of small earthquakes located in regions of previous seamount subduction, with variations in earthquake stress drop reflecting potentially disrupted upper plate material deformed as a seamount passed.&amp;#160; Other variations in earthquake location and stress drop can be correlated with observed geodetic locking variations.&amp;#160;&lt;/p&gt;

scholarly journals K‐Ar Dating of Fossil Seismogenic Thrusts in the Shimanto Accretionary Complex, Southwest Japan

Tectonics ◽  
2019 ◽  
Vol 38 (11) ◽  
pp. 3866-3880 ◽  
Author(s):  
Donald M. Fisher ◽  
Satoshi Tonai ◽  
Yoshitaka Hashimoto ◽  
Naotaka Tomioka ◽  
David Oakley
Keyword(s):  
Accretionary Complex ◽  
Southwest Japan

scholarly journals Fault rocks and past to recent fluid characteristics from the borehole survey of the Nojima fault ruptured in the 1995 Kobe earthquake, southwest Japan

2000 ◽  
Vol 105 (B7) ◽  
pp. 16161-16171 ◽  
Author(s):  
Tomoyuki Ohtani ◽  
Koichiro Fujimoto ◽  
Hisao Ito ◽  
Hidemi Tanaka ◽  
Naoto Tomida ◽  
...  
Keyword(s):  
Southwest Japan ◽  
Fault Rocks ◽  
Kobe Earthquake ◽  
Nojima Fault ◽  
Fluid Characteristics

Style of fluid flow and deformation in and around an ancient out-of-sequence thrust: An example from the Nobeoka Tectonic Line in the Shimanto accretionary complex, Southwest Japan

Island Arc ◽  
2009 ◽  
Vol 18 (2) ◽  
pp. 333-351 ◽  
Author(s):  
Hideki Mukoyoshi ◽  
Tetsuro Hirono ◽  
Hidetoshi Hara ◽  
Kotaro Sekine ◽  
Noriyoshi Tsuchiya ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Accretionary Complex ◽  
Southwest Japan ◽  
Tectonic Line
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