Slow earthquakes illuminating interplate coupling heterogeneities in subduction zones

AbstractPhase transformations greatly affect physical properties of rocks and impose a first-order control on geodynamic processes. Under high deformation rates, rheological heterogeneities cause large spatial variations of stress in materials. Until now, the impact of higher deformation rates, rock heterogeneity and stress build up on phase transformations and material properties is not well understood. Here we show, that phase transitions are controlled by the stress build-up during fast deformation. In a deformation experiment (600 °C, 1.47 GPa), rock heterogeneity was simulated by a strong elliptical alumina inclusion in a weak calcite matrix. Under deformation rates comparable to slow earthquakes, calcite transformed locally to aragonite matching the distribution of maximum principal stresses and pressure (mean stress) from mechanical models. This first systematic investigation documents that phase transformations occur in a dynamic system during deformation. The ability of rocks to react during fast deformation rates may have serious consequences on rock rheology and thus provide unique information on the processes leading to giant ruptures in subduction zones.

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Complexity of low-frequency earthquakes activity in western Shikoku

10.5194/egusphere-egu2020-15224 ◽

2020 ◽

Author(s):

Natalia Poiata ◽

Jean-Pierre Vilotte ◽

Nikolai Shapiro ◽

Mariano Supino ◽

Kazushige Obara

Keyword(s):

Subduction Zones ◽

Large Scale ◽

Active Faults ◽

Low Frequency ◽

Space Time ◽

Interaction Patterns ◽

Slow Slip Events ◽

Time Activity ◽

Tectonic Tremor ◽

Slow Earthquakes

Short-duration transient seismic events known as low-frequency earthquakes (LFEs) are a component of the slow earthquakes family observed in the transition zone, at the root of seismogenic regions of the subduction zones or active faults. LFEs are the signature of impulse seismic energy radiation associated to and often mixed within complex tectonic tremor signal. Detailed analysis and characterization of LFE space-time activity in relation to other slow earthquake phenomena can provide important information about the state and the processes of fault interface.We derive a catalog of LFEs in western Shikoku (Japan) by applying a full waveform coherency-based detection and location method to the 4-year continuous data covering the period of 2013-2016 and recorded at Hi-net seismic stations of NIED. The obtained catalog of over 150,000 detected events allows looking into the details of LFE space-time activity during the tectonic tremor sequences and inter-sequence periods.We use this catalogue of LFEs to perform a systematic statistical analysis of the event occurrence patterns by applying correlation and clustering analysis to infer the large-scale (long temporal ~ 1-2 day duration) space-time characteristics and interaction patterns of activity and its potential relation to the structural complexity of the subducting plate. We also analyze the correlation between the migration of clustered LFE activity during energetic tremor sequences and short-term slow slip events occurring in the area during the analyzed period.

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The Chile subduction zone : Nature of the lithosphere between alternating regions of slow earthquakes versus non slow earthquakes

10.5194/egusphere-egu2020-4035 ◽

2020 ◽

Author(s):

Pousali Mukherjee ◽

Yoshihiro Ito ◽

Emmanuel S. Garcia ◽

Raymundo Plata-Martinez ◽

Takuo Shibutani

Keyword(s):

Subduction Zones ◽

Receiver Function ◽

Function Analysis ◽

Fluid Distribution ◽

Inversion Method ◽

Megathrust Earthquakes ◽

Slow Earthquake ◽

Slow Earthquakes ◽

Receiver Function Analysis ◽

Earthquake Area

Subduction zones host some of the greatest megathrust earthquakes in the world. Slow earthquakes have been discovered around the subduction zones of the Pacific rim very close to megathrust earthquakes. Investigating the lithosphere of the slow earthquake area versus non slow-earthquake area in subduction zones is crucial in understanding the role of the internal structure to control slow earthquakes. In this study, we investigate the lithospheric structure of stations in the slow earthquake area and non slow-earthquake areas in Chile using receiver function analysis and inversion method using teleseismic earthquakes. Here we focus on, especially the Vp/Vs ratios from both slow and non-slow earthquake areas, because the Vp/Vs ratio is sensitive to the fluid distribution in the lithosphere; the fluid distribution possibly controls the potential occurrence of slow earthquakes. Additionally, the nature of the slab can also play a crucial factor. The Vp/Vs ratio results across depth shows significantly higher value in the deeper oceanic slab region beneath the stations in the slow earthquake areas with higher contrast at the boundary.

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An intraplate slow earthquake observed by a dense GPS network in Hokkaido, northernmost Japan

Geophysical Journal International ◽

10.1093/gji/ggu380 ◽

2014 ◽

Vol 200 (1) ◽

pp. 144-148 ◽

Cited By ~ 1

Author(s):

Mako Ohzono ◽

Hiroaki Takahashi ◽

Masayoshi Ichiyanagi

Keyword(s):

Subduction Zones ◽

Earthquake Swarm ◽

Tectonic Activity ◽

Maximum Magnitude ◽

Slow Slip ◽

Localized Deformation ◽

Slow Earthquake ◽

Magnitude Scaling ◽

Duration Magnitude ◽

Slow Earthquakes

Abstract An intraplate slow earthquake was detected in northernmost Hokkaido, Japan, by a dense network of the global navigation satellite system. Transient abnormal acceleration of <12 mm was observed during the period 2012 July to 2013 January (∼5.5 months) at several sites. The spatial displacement distribution suggests that a localized tectonic event caused localized deformation. Estimated fault parameter indicates very shallow-dip reverse faulting in the uppermost crust, with a total seismic moment of 1.75E + 17 N m (Mw 5.4). This fault geometry is probably consistent with detachment structure indicated by geological studies. A simultaneous earthquake swarm with the maximum magnitude M4.1 suggests a possibility that the slow slip triggered the seismic activity for unknown reasons. This slow earthquake is slower than its moment would indicate, with a duration–magnitude scaling relationship unlike either regular earthquakes or subduction slow slip events. This result indicates that even if the area is under different physical property from subduction zones, slow earthquake can occur by some causes. Slow earthquakes exist in remote regions away from subduction zones and might play an important role in strain release and tectonic activity.

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Seismic Moment, Seismic Energy, and Source Duration of Slow Earthquakes: Application of Brownian slow earthquake model to three major subduction zones

Geophysical Research Letters ◽

10.1002/2018gl077461 ◽

2018 ◽

Vol 45 (7) ◽

pp. 3059-3067 ◽

Cited By ~ 11

Author(s):

Satoshi Ide ◽

Julie Maury

Keyword(s):

Seismic Moment ◽

Subduction Zones ◽

Seismic Energy ◽

Slow Earthquake ◽

Slow Earthquakes ◽

Earthquake Model ◽

Source Duration

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Plastic flow of omphacite in eclogites at temperatures below 500°C – implications for interplate coupling in subduction zones

International Journal of Earth Sciences ◽

10.1007/s005310000159 ◽

2001 ◽

Vol 90 (1) ◽

pp. 197-210 ◽

Cited By ~ 28

Author(s):

Dörthe Piepenbreier ◽

Bernhard Stöckhert

Keyword(s):

Plastic Flow ◽

Subduction Zones ◽

Interplate Coupling

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Enhancement of Interplate Coupling after Recent Megathrust Earthquakes

10.5194/egusphere-egu2020-2550 ◽

2020 ◽

Author(s):

Mohammad Yuzariyadi ◽

Kosuke Heki

Keyword(s):

Subduction Zones ◽

Megathrust Earthquakes ◽

The North ◽

Rupture Area ◽

Interplate Coupling ◽

Maule Earthquake ◽

Megathrust Faults ◽

Adjacent Segments ◽

Gnss Data ◽

Ne Japan

Enhanced interplate coupling has been found for segments adjacent along-strike to megathrust faults after the 2003 Tokachi-Oki and the 2011 Tohoku-Oki earthquakes, NE Japan, and was interpreted as acceleration of the subducting Pacific Plate slab. A similar enhanced coupling was also reported for the segments to the north of the rupture area of the 2010 Maule earthquake, central Chile. We utilize available GNSS data to find such enhanced coupling in worldwide subduction zones including NE Japan, central and northern Chile, Sumatra, and Mexico to investigate their common features. Our study revealed that the accelerations of landward movement of 2.1-9.0 mm per year appeared in adjacent segments following the 2014 Iquique (Chile), the 2007 Bengkulu (Sumatra), and the 2012 Oaxaca (Mexico) earthquakes. We also confirmed that the enhanced coupling is associated with the increase of seismicity for all these six cases. We found that the degree of enhancement depends on the length of the slab and the magnitude of the earthquake, which is consistent with the simple 2-dimensional model proposed earlier.

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