On the deformation cycle of a strongly coupled plate interface: The triple earthquakes of 16 March 1963, 15 November 2006, and 13 January 2007 along the Kurile subduction zone

2009 ◽  
Vol 114 (B10) ◽  
Author(s):  
M. Raeesi ◽  
K. Atakan
Keyword(s):  
Subduction Zone ◽  
Plate Interface ◽  
Strongly Coupled ◽  
Deformation Cycle

The influence of fluids in the unusually high-rate seismicity in the Ometepec segment of the Mexican subduction zone

2021 ◽  
Author(s):  
D Legrand ◽  
A Iglesias ◽  
S K Singh ◽  
V Cruz-Atienza ◽  
C Yoon ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Temporal Distribution ◽  
Aftershock Sequence ◽  
High Rate ◽  
Earth Tides ◽  
P Value ◽  
Plate Interface ◽  
Flow Measurements ◽  
Slow Slip Events ◽  
Mexican Subduction Zone

Summary The rate of earthquakes with magnitudes Mw ≤ 7.5 in the Ometepec segment of the Mexican subduction zone is relatively high as compared to the neighboring regions of Oaxaca and Guerrero. Although the reason is not well understood, it has been reported that these earthquakes give rise to a large number of aftershocks. Our study of the aftershock sequence of the 2012 Mw7.4 Ometepec thrust earthquake suggests that it is most likely due to two dominant factors: (1) The presence of an anomalously high quantity of over-pressured fluids near the plate interface, and (2) the roughness of the plate interface. More than 5,400 aftershocks were manually detected during the first ten days following the 2012 earthquake. Locations were obtained for 2,419 events (with duration magnitudes Md ≥ 1.5). This is clearly an unusually high number of aftershocks for an earthquake of this magnitude. Furthermore, we generated a more complete catalog, using an unsupervised fingerprint technique, to detect more smaller events (15,593 within one month following the mainshock). For this catalog, a high b-value of 1.50 ± 0.10 suggests the presence of fluid release during the aftershock sequence. A low p-value (0.37 ± 0.12) of the Omori law reveals a slow decaying aftershock sequence. The temporal-distribution of aftershocks shows peaks of activity with two dominant periods of 12h and 24h that correlate with the Earth tides. To explain these observations, we suggest that the 2012 aftershock sequence is associated with the presence of over-pressured fluids and/or a heterogeneous and irregular plate interface related to the subduction of the neighboring seamounts. High fluid content has independently been inferred by magneto-telluric surveys and deduced from heat flow measurements in the region. The presence of fluids in the region has also been proposed to explain the occurrence of slow slip events, low frequency earthquakes, and tectonic tremors.

scholarly journals STRUCTURAL AND EARTHQUAKE EVALUATIONS ALONG JAVA SUBDUCTION ZONE, INDONESIA

2020 ◽  
Vol 30 (1) ◽  
pp. 65
Author(s):  
Adi Patria ◽  
Atin Nur Aulia
Keyword(s):  
Subduction Zone ◽  
Normal Fault ◽  
Thrust Fault ◽  
Earthquake Activity ◽  
Accretionary Wedge ◽  
Forearc Basin ◽  
Plate Interface ◽  
Seafloor Morphology ◽  
Australian Plate ◽  
Seismic Reflection Profiles

Java Subduction is a zone of trench perpendicular convergence of Australian Plate and Southeast Asia in the south of Java. It is characterized by an almost E-W trending trench with an eastward increase of convergence velocity. Three major earthquakes with tsunamis have been caused by deformation along this subduction zone. Although many studies have undertaken to understand the nature of the subduction system, a clear relationship between structures and earthquake activities remains poorly explained. In this study, we used bathymetry, residual bathymetry, and published seismic reflection profiles to evaluate structural and morphological elements, then link the observations to earthquake activity along Java Subduction Zone. Based on seafloor morphology, characteristics of the accretionary wedge and forearc basin varies along the trench in response to the variation of seafloor morphology. Features such as seamounts and ridges which were observed in the oceanic basin may be subducted beneath accretionary wedge and disrupt the morphology of accretionary wedge, forearc basin, and trench. Earthquake activities are generally dominated by normal fault solutions in the trench, which is attributed to plate bending faults while thrust fault solution is observed in the forearc basin area. Thrust fault activities in accretionary wedge are decreased to the east, where there is no thrust fault solution observed in the eastern end of the subduction zone. Few strike-slip focal mechanisms are observed and mainly located within the subducting oceanic plate. Structures and subducting oceanic features may control the earthquake activity where deformation occurred at the edge of these features. The two largest thrust fault earthquakes in 1994 and 2006 are interpreted as a result of deformation along with plate interface on soft or unconsolidated sediment above the incoming plate. The largest normal fault earthquake with a magnitude 8.3 is possibly caused by a crustal scale-fault that breaks the entire oceanic crust.ABSTRAK - Evaluasi struktur dan gempa bumi di sepanjang zona subduksi Jawa, Indonesia. Subduksi Jawa adalah zona konvergensi yang tegak lurus palung antara Lempeng Australia dan Asia Tenggara di selatan Jawa. Hal ini ditandai dengan palung berarah hampir barat–timur dengan peningkatan kecepatan konvergensi ke arah timur. Tiga gempa bumi besar dengan tsunami disebabkan oleh deformasi di sepanjang zona subduksi ini. Meskipun banyak penelitian telah dilakukan untuk memahami sifat sistem subduksi, hubungan antara struktur dan kegiatan gempa bumi masih kurang jelas. Dalam studi ini, kami menggunakan batimetri, batimetri residual, dan profil refleksi seismik untuk mengevaluasi elemen struktur dan morfologi, kemudian menghubungkan pengamatan dengan aktivitas gempa bumi di sepanjang zona subduksi Jawa. Berdasarkan morfologi dasar laut, karakteristik prisma akresi dan cekungan busur muka bervariasi di sepanjang palung sebagai respon terhadap variasi morfologi dasar laut. Fitur seperti seamount dan punggungan yang diamati di cekungan samudera menunjam di bawah prisma akresi dan mengganggu morfologi prisma akresi, cekungan busur muka, dan palung. Aktivitas gempa bumi umumnya didominasi oleh patahan normal di palung, yang dikaitkan dengan patahan tekukan lempeng sedangkan patahan naik diamati di daerah cekungan busur muka. Aktivitas sesar naik di dalam prisma akresi berkurang ke arah timur, di mana tidak ada patahan naik yang teramati di ujung timur zona subduksi. Beberapa mekanisme patahan mendatar diamati dan terutama terletak di dalam lempeng samudera yang menunjam. Struktur dan fitur di kerak samudra yang menunjam dapat mengontrol aktivitas gempa bumi di mana deformasi terjadi di tepian fitur ini. Dua gempa bumi besar dengan sifat patahan naik pada tahun 1994 dan 2006 ditafsirkan sebagai hasil dari deformasi di sepanjang antarmuka lempeng pada sedimen lunak atau tidak terkonsolidasi di atas lempeng yang masuk. Gempa bumi besar dengan sifat sesar normal magnitude 8,3 mungkin disebabkan oleh patahan skala-kerak yang menghancurkan seluruh kerak samudera.

scholarly journals Fluid Transport and Storage in the Cascadia Forearc inferred from Magnetotelluric Data

2021 ◽  
Author(s):  
Gary Egbert ◽  
Bo Yang ◽  
Paul A. Bedrosian ◽  
Kerry Key ◽  
Dean Livelybrooks ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Subduction Zone ◽  
Fluid Transport ◽  
Critical Role ◽  
Three Dimensional ◽  
Oceanic Lithosphere ◽  
Cascadia Subduction Zone ◽  
Plate Interface ◽  
Magnetotelluric Data ◽  
And Storage

Abstract Subduction of hydrated oceanic lithosphere can carry water deep into the Earth, with important consequences for a range of tectonic and magmatic processes. Most fluid is released at relatively shallow depths in the forearc where it is thought to play a critical role in controlling mechanical properties and seismic behavior of the subduction megathrust. Here we present results from three-dimensional inversion of nearly 400 long-period magnetotelluric sites, including 64 offshore, to provide new insights into the distribution of fluids in the forearc of the Cascadia subduction zone. Our amphibious dataset provides new constraints on the geometry of the electrically resistive Siletzia terrane, a thickened section of oceanic crust accreted to North America in the Eocene, and the conductive accretionary complex, which is being underthrust all along the margin. Fluids accumulate, over time-scales likely exceeding 1 My, above the plate interface in metasedimentary units, while the mafic rocks of Siletzia remain dry. Fluids in metasediments tend to peak at fixed slab-depths of 17.5 and 30 km, suggesting control by metamorphic processes, but also concentrate around the edges of Siletzia, suggesting that this mafic block is impermeable, with dehydration fluids escaping up-dip along the megathrust. Our results demonstrate that lithology of the overriding crust can play a critical role in controlling fluid transport and sequestration in a subduction zone, with potentially important implications for mechanical properties.

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

<p>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.</p><p>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.</p>

Triggering an Unexpected Earthquake in an Uncoupled Subduction Zone

2021 ◽  
Author(s):  
Kevin P. Furlong ◽  
Matthew W. Herman
Keyword(s):  
Subduction Zone ◽  
Plate Boundary ◽  
Strike Slip ◽  
Seismic Gap ◽  
Plate Interface ◽  
Thrust Faulting ◽  
Current Thinking ◽  
Abstract Submission ◽  
Geologic Record ◽  
Eastern Edge

<p>In the 1970’s, the Shumagin Islands region of the Alaska subduction zone was identified as a seismic gap expected to host a future great (Mw >8.0) earthquake. More recent geodetic data indicate this region is poorly coupled, and the geologic record shows little evidence of past large events - leading to current thinking of the “Shumagin Gap” as a region of low seismic hazard. From July to October 2020 (with aftershocks continuing through the time of this abstract submission in January), a series of earthquakes occurred in this region, potentially incompatible with this low-coupling interpretation. The initial Mw 7.8 plate interface thrust faulting earthquake on July 21st straddled the eastern edge of the Shumagin Gap, followed by an Mw 7.6 strike-slip earthquake on October 19th within the slab under the eastern side of the Shumagin Gap. Stress modeling indicates that this strike-slip earthquake is in fact favored if the Shumagin Gap has low coupling, whereas a highly coupled Shumagin Gap would inhibit that type and location of earthquake. The initial thrust earthquake and its afterslip significantly enhanced the strike-slip stress loading within the subducting slab, helping to trigger that event. We find that although regions such as the Shumagin Gap have a low seismogenic potential for plate interface thrusting, the existence of this decoupled region increases the potential for intra-plate strike-slip faulting in association with more typical subduction earthquakes on adjacent coupled segments of the plate boundary. Therefore, the seismic and tsunami potential near these uncoupled regions might be greater than previously thought.</p>

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