Long-term seafloor and land-based sesismological monitoring at southwestern end of the Kurile subduction zone, based on more than six-year continuous observation

2007 ◽  
Author(s):  
T. Watanabe ◽  
H. Mikada ◽  
M. Kasahara
Keyword(s):  
Subduction Zone ◽  
Continuous Observation

Long-Term Interactions Between Intermediate Depth and Shallow Seismicity in North Chile Subduction Zone

2017 ◽  
Vol 44 (18) ◽  
pp. 9283-9292 ◽  
Author(s):  
Jorge Jara ◽  
Anne Socquet ◽  
David Marsan ◽  
Michel Bouchon
Keyword(s):  
Subduction Zone ◽  
Intermediate Depth

scholarly journals Long-term Monitoring in Deep Boreholes in the Nankai Subduction Zone

2007 ◽  
Vol SpecialIssue ◽  
pp. 117-119 ◽  
Author(s):  
H. Ito
Keyword(s):  
Subduction Zone ◽  
Nankai Subduction Zone ◽  
Long Term Monitoring ◽  
Deep Boreholes ◽  
Term Monitoring

No abstract available. <br><br> doi:<a href="http://dx.doi.org/10.2204/iodp.sd.s01.43.2007" target="_blank">10.2204/iodp.sd.s01.43.2007</a>

scholarly journals Accretion-controlled forearc deformation pulses recorded by high-pressure paleo-accretionary wedges: the example of the Hellenic subduction zone

2021 ◽  
Author(s):  
Armel Menant ◽  
Onno Oncken ◽  
Johannes Glodny ◽  
Samuel Angiboust ◽  
Laurent Jolivet ◽  
...  
Keyword(s):  
High Pressure ◽  
Subduction Zone ◽  
Numerical Models ◽  
Carbonaceous Material ◽  
Plate Interface ◽  
Stress Regime ◽  
Hellenic Subduction Zone ◽  
Driving Mechanisms ◽  
Wide Range

&lt;p&gt;Subduction margins are the loci of a wide range of deformation processes occurring at different timescales along the plate interface and in the overriding forearc crust. Whereas long-term deformation is usually considered as stable over Myr-long periods, this vision is challenged by an increasing number of observations suggesting a long-term pulsing evolution of active margins. To appraise this emerging view of a highly dynamic subduction system and identify the driving mechanisms, detailed studies on high pressure-low temperature (HP-LT) exhumed accretionary complexes are crucial as they open a window on the deformation history affecting the whole forearc region.&lt;/p&gt;&lt;p&gt;In this study, we combine structural and petrological observations, Raman spectroscopy on carbonaceous material, Rb/Sr multi-mineral geochronology and thermo-mechanical numerical models to unravel with an unprecedented resolution the tectono-metamorphic evolution of the Late-Cenozoic HP-LT nappe stack cropping out in western Crete (Hellenic subduction zone). A consistent decrease of peak temperatures and deformation ages toward the base of the nappe pile allows us to identify a minimum of three basal accretion episodes between ca. 24 Ma and ca. 15 Ma. On the basis of structural evidences and pressure-temperature-time-strain predictions from numerical modeling, we argue that each of these mass-flux events triggered a pulse in the strain rate, sometimes associated with a switch of the stress regime (i.e., compressional/extensional). Such accretion-controlled transient deformation episodes last at most ca. 1-2 Myr and may explain the poly-phased structural records of exhumed rocks without involving changes in far-field stress conditions. This long-term background tectonic signal controlled by deep accretionary processes plays a part in active deformations monitored at subduction margins, though it may remain blind to most of geodetic methods because of superimposed shorter-timescale transients, such as seismic-cycle-related events.&lt;/p&gt;

scholarly journals Detection of deep low-frequency earthquakes in the Nankai subduction zone over 11 years using a matched filter technique

2020 ◽  
Author(s):  
Aitaro Kato ◽  
Shigeki Nakagawa
Keyword(s):  
Subduction Zone ◽  
Matched Filter ◽  
Low Frequency ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Filter Technique ◽  
Episodic Tremor And Slip ◽  
Nankai Subduction Zone ◽  
Spatio Temporal

Abstract To improve our understanding of the long-term behavior of low-frequency earthquakes (LFEs) along the tremor belt of the Nankai subduction zone, we applied a matched filter technique to continuous seismic data recorded by a dense and highly sensitive seismic network over an 11 year window, April 2004 to August 2015. We detected a total of ~510,000 LFEs, or ~23× the number of LFEs in the JMA catalog for the same period. During long-term slow slip events (SSEs) in the Bungo Channel, a series of migrating LFE bursts intermittently occurred along the fault-strike direction, with slow hypocenter propagation. Elastic energy released by long-term SSEs appears to control the extent of LFE activity. We identify slowly migrating fronts of LFEs during major episodic tremor and slip (ETS) events, which extend over distances of up to 100 km and follow diffusion-like patterns of spatial evolution with a diffusion coefficient of ~10 4 m 2 /s. This migration pattern closely matches the spatio-temporal evolution of tectonic tremors reported by previous studies. At shorter distances, up to 15 km, we discovered rapid diffusion-like migration of LFEs with a coefficient of ~10 5 m 2 /s. We also recognize that rapid migration of LFEs occurred intermittently in many streaks during major ETS episodes. These observations suggest that slow slip transients contain a multitude of smaller, temporally clustered fault slip events whose evolution is controlled by a diffusional process.

An investigation on possibilty of creep on the Makran subduction zone based on deformation data

2020 ◽  
Author(s):  
Homa Ghadimi Moghaddam ◽  
Alireza Khodaverdian ◽  
Hamid Zafarani
Keyword(s):  
Subduction Zone ◽  
Weighted Least Squares ◽  
Element Model ◽  
Fault Slip ◽  
Deformation Model ◽  
Slip Rates ◽  
Makran Subduction Zone ◽  
Fault Slip Rates ◽  
Seismic Deformation

&lt;p&gt;Long term crustal flow of the Makran subduction zone is computed with a kinematic finite element model based on iterated weighted least squares fits to data. Data include 91 fault traces, 56 fault offset rates, 76 geodetic velocities, 1962 principal stress azimuths, and velocity boundary conditions. Model provides long-term fault slip rates, velocity, and distributed permanent strain rates between faults in the Makran region from all available kinematic data. Due to low seismicity of western Makran compared to its eastern part we defined two models to evaluate the possibility of creep in the Iranian Makran subduction. One model assumes that geodetic velocities measured adjacent to the Makran subduction zone reflect a temporarily locked subduction zone will be referred to as the &amp;#8220;seismic deformation model&amp;#8221;. In contrast, another model called the &amp;#8220;half creeping deformation model&amp;#8221; assumes that the western part of Makran may creep smoothly without any locking. In order to verify the models, the estimates of fault slip rates are compared to slip rates from merely analysing geodetic benchmark velocities or paleoseismological studies or published geological rates which have not been used in the model. Our estimated rates are all in the range of geodetic rates and are even more consistent with geological rates than previous GPS-based estimates. Another verification for the model is comparison of the computed interseismic velocities at GPS benchmarks to GPS measurements. While neither model accurately predicts these interseismic velocities at benchmarks, the half creeping deformation model is more accurate for Chabahar station than the seismic deformation model. These results have important earthquake and tsunami hazard implications. For example, Fault slip rates are the main component of time-dependent seismic hazard studies and can be used to estimate activity rates for more sophisticated earthquake models.&lt;/p&gt;

scholarly journals Occurrence of Graphite-Like Carbon in Podiform Chromitites of Greece and Its Genetic Significance

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 152 ◽  
Author(s):  
Maria Economou-Eliopoulos ◽  
George Tsoupas ◽  
Vasilis Skounakis
Keyword(s):  
Subduction Zone ◽  
Mineral Chemistry ◽  
Present Contribution ◽  
Term Evolution ◽  
Wide Range ◽  
Carbon Recycling ◽  
Podiform Chromitites ◽  
Of Greece

The role of post-magmatic processes in the composition of chromitites hosted in ophiolite complexes, the origin of super-reduced phases, and factors controlling the carbon recycling in a supra-subduction zone environment are still unclear. The present contribution compiles the first scanning electron microscope/energy-dispersive (SEM/EDS) data on graphite-like amorphous carbon, with geochemical and mineral chemistry data, from chromitites of the Skyros, Othrys, Pindos, and Veria ophiolites (Greece). The aim of this study was the delineation of potential relationships between the modified composition of chromite and the role of redox conditions, during the long-term evolution of chromitites in a supra-subduction zone environment. Chromitites are characterized by a strong brittle (cataclastic) texture and the presence of phases indicative of super-reducing phases, such as Fe–Ni–Cr-alloys, awaruite (Ni3Fe), and heazlewoodite (Ni3S2). Carbon-bearing assemblages are better revealed on Au-coated unpolished sections. Graphite occurs in association with hydrous silicates (chlorite, serpentine) and Fe2+-chromite, as inclusions in chromite, filling cracks within chromite, or as nodule-like graphite aggregates. X-ray spectra of graphite–silicate aggregates showed the presence of C, Si, Mg, Al, O in variable proportions, and occasionally K and Ca. The extremely low fO2 during serpentinization facilitated the occurrence of methane in microfractures of chromitites, the precipitation of super-reducing phases (metal alloys, awaruite, heazlewoodite), and graphite. In addition, although the origin of Fe–Cu–Ni-sulfides in ultramafic parts of ophiolite complexes is still unclear, in the case of the Othrys chromitites, potential reduction-induced sulfide and/or carbon saturation may drive formation of sulfide ores and graphite-bearing chromitites. The presented data on chromitites covering a wide range in platinum-group element (PGE) content, from less than 100 ppb in the Othrys to 25 ppm ΣPGE in the Veria ores, showed similarity in the abundance of graphite-like carbon. The lack of any relationship between graphite (and probably methane) and the PGE content may be related to the occurrence of the (Ru–Os–Ir) minerals in chromitites, which occur mostly as oxides/hydroxides, and to lesser amounts of laurite, with pure Ru instead activating the stable CO2 molecule and reducing it to methane (experimental data from literature).

A Review on Long-Term Evaluation of Occurrence Probability for Subduction-Zone Earthquakes in Eastern Japan

2012 ◽  
Vol 166-169 ◽  
pp. 2190-2196 ◽  
Author(s):  
Zheng Ru Tao ◽  
Xia Xin Tao ◽  
Wei Jiang
Keyword(s):  
Subduction Zone ◽  
Tohoku Earthquake ◽  
Large Earthquake ◽  
Occurrence Probability ◽  
Evaluation Approach ◽  
The Pacific ◽  
Term Evaluation ◽  
Subduction Zone Earthquakes ◽  
Eastern Japan

Evaluation approach of occurrence probability for subduction-zone earthquakes adopted in “National Seismic Hazard Maps for Japan” is reviewed, especially for the area of the 2011 off the Pacific coast of Tohoku Earthquake (2011 Tohoku Earthquake in short). One problem is pointed that the occurrence probability of such a large earthquake cannot be predicted just from seismicity in a region small like Miyagi-ken-Oki area or southern Sanriku-Oki. The whole subduction zone in eastern Japan is suggested to be taken into account with the interaction between the energy released in quakes. Finally, a simple test to predict the next large earthquake in the subduction-zone by means of Artificial Neural Network is presented, and the result for the years of 2008-2018 shows there may be an earthquake with magnitude up to 8.8 in the zone.

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