Slab2, a comprehensive subduction zone geometry model

Science ◽  
2018 ◽  
Vol 362 (6410) ◽  
pp. 58-61 ◽  
Author(s):  
Gavin P. Hayes ◽  
Ginevra L. Moore ◽  
Daniel E. Portner ◽  
Mike Hearne ◽  
Hanna Flamme ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Active Faults ◽  
Three Dimensional ◽  
Spatial Extent ◽  
Geometrical Analysis ◽  
Geometry Model ◽  
Subduction Zone Earthquakes

Subduction zones are home to the most seismically active faults on the planet. The shallow megathrust interfaces of subduction zones host Earth’s largest earthquakes and are likely the only faults capable of magnitude 9+ ruptures. Despite these facts, our knowledge of subduction zone geometry—which likely plays a key role in determining the spatial extent and ultimately the size of subduction zone earthquakes—is incomplete. We calculated the three-dimensional geometries of all seismically active global subduction zones. The resulting model, called Slab2, provides a uniform geometrical analysis of all currently subducting slabs.

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

<p>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.  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.  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.  Estimates of small earthquake locations and stress drop are presented in each location, utilizing data from coastal and/or ocean bottom seismic stations.  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.  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.  Other variations in earthquake location and stress drop can be correlated with observed geodetic locking variations. </p>

scholarly journals Illuminating subduction zone rheological properties in the wake of a giant earthquake

2019 ◽  
Vol 5 (12) ◽  
pp. eaax6720 ◽  
Author(s):  
Jonathan R. Weiss ◽  
Qiang Qiu ◽  
Sylvain Barbot ◽  
Tim J. Wright ◽  
James H. Foster ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Three Dimensional ◽  
Surface Strain ◽  
Postseismic Deformation ◽  
Crust And Upper Mantle ◽  
Plate Convergence ◽  
Maule Earthquake ◽  
History Of ◽  
Dependent Viscosity

Deformation associated with plate convergence at subduction zones is accommodated by a complex system involving fault slip and viscoelastic flow. These processes have proven difficult to disentangle. The 2010 Mw 8.8 Maule earthquake occurred close to the Chilean coast within a dense network of continuously recording Global Positioning System stations, which provide a comprehensive history of surface strain. We use these data to assemble a detailed picture of a structurally controlled megathrust fault frictional patchwork and the three-dimensional rheological and time-dependent viscosity structure of the lower crust and upper mantle, all of which control the relative importance of afterslip and viscoelastic relaxation during postseismic deformation. These results enhance our understanding of subduction dynamics including the interplay of localized and distributed deformation during the subduction zone earthquake cycle.

Main Results from the Program Promotion Panel for Subduction-Zone Earthquakes

2020 ◽  
Vol 15 (2) ◽  
pp. 87-95
Author(s):  
Kazushige Obara ◽  
Takuya Nishimura ◽  
◽  
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Deep Understanding ◽  
Disaster Mitigation ◽  
Observational Research ◽  
Earthquake Activity ◽  
Megathrust Earthquakes ◽  
Slow Earthquakes ◽  
Occurrence Mechanism ◽  
Subduction Zone Earthquakes

Understanding the occurrence mechanism of subduction zone earthquakes scientifically is intrinsically important for not only forecast of future subduction earthquakes but also disaster mitigation for strong ground motion and tsunami accompanied by large earthquakes. The Program Promotion Panel for Subduction-zone earthquakes mainly focused on interplate megathrust earthquakes in the subduction zones and the research activity included collection and classification of historical data on earthquake phenomena, clarifying the current earthquake phenomena and occurrence environment of earthquake sources, modelling earthquake phenomena, forecast of further earthquake activity based on monitoring crustal activity and precursory phenomena, and development of observation and analysis technique. Moreover, we studied the occurrence mechanism of intraslab earthquakes within the subducting oceanic plate. Five-year observational research program actually produced enormous results for deep understanding of subduction zone earthquakes phenomena, especially in terms of slow earthquakes, infrequent huge earthquakes, and intraslab earthquakes. This paper mainly introduces results from researches on these phenomena in subduction zones.

Three-dimensional temperature variations in a fossil subduction zone resolved by RSCM thermometry (Tauern Window, Eastern Alps)

2020 ◽  
Author(s):  
Philip Groß ◽  
Jan Pleuger ◽  
Mark R. Handy ◽  
Timm John
Keyword(s):  
Temperature Field ◽  
Subduction Zone ◽  
Cross Section ◽  
Subduction Zones ◽  
Thermal State ◽  
Three Dimensional ◽  
Eastern Alps ◽  
Peak Temperature ◽  
Temperature Variations ◽  
Tauern Window

<p>Knowledge on the thermal state of orogens and subduction zones is crucial in trying to understand the processes that take place in these zones, since temperature controls, e.g., rock strength, metamorphic reactions and fluid flow. These are all critical parameters for the dynamics of orogens and subduction zones and conversely, these parameters feed back on the thermal state in various ways. We investigated an example of a former subduction zone, exposed in the central Tauern Window (Eastern Alps), with the aim of reconstructing its three-dimensional temperature variations.</p><p>Structural and petrological observations in the central Tauern Window reveal a tens-of-kilometre-scale sheath fold that formed under high-pressure (HP) conditions (ca. 2 GPa). The fold is a composite structure that isoclinally folded the thrust of an oceanic nappe derived from Alpine Tethys onto a unit of the distal European continental margin, also affected by HP conditions. This structural assemblage is preserved between two younger domes at either end of the Tauern Window. The domes are associated with temperature-dominated Barrow-type metamorphism that overprints the HP-metamorphism partly preserved in the sheath fold.</p><p>Using Raman spectroscopy on carbonaceous material (RSCM) on 100 samples from this area, we were able to distinguish domains with the original, subduction-related peak temperature conditions from domains that were overprinted during later temperature-dominated (Barrovian) metamorphism. The distribution of RSCM-temperatures in the Barrovian domains indicates a decrease of peak temperature with increasing distance from the centres of the thermal domes, both in map view and cross section. This represents a geotherm where paleo-temperature increases downward, in line with previous studies using, e.g., oxygen isotope fractionation and calcite-dolomite equilibria. However, we observe the opposite temperature trend in the lower limb of the sheath fold, viz., tendentially an upward increase in paleo-temperature. We interpret this inverted temperature domain as the relic of a subduction-related temperature field. Towards the central part of the sheath fold’s upper limb, measured temperatures increase to a maximum of ca. 520°C. Further upsection in the hanging wall of the sheath fold, temperatures decrease to where they are indistinguishable from the peak temperatures of the overprinting Barrovian metamorphism. Isograds (i.e. contours of equal peak-temperature) are oriented roughly parallel to the nappe contacts and lithological layering, which results in an eye-shaped concentric isograd pattern in cross-section. This reflects a sheath-like three-dimensional geometry of the isograds. We propose the following hypothesis to explain the subduction-related peak-temperature pattern: The pattern reflects sheath folding of a subduction-related temperature field. Possibly, sheath folding occurred during exhumation, after the equilibration at peak pressure and temperature conditions. The preservation of the pattern implies fast exhumation and cooling of the rocks.</p>

scholarly journals 3D anisotropic structure of the Japan subduction zone

2021 ◽  
Vol 7 (4) ◽  
pp. eabc9620 ◽  
Author(s):  
Zewei Wang ◽  
Dapeng Zhao
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Seismic Anisotropy ◽  
Three Dimensional ◽  
Mantle Flow ◽  
Anisotropic Structure ◽  
Time Data ◽  
Material Recycling ◽  
Tomographic Method ◽  
Japan Subduction Zone

How mantle materials flow and how intraslab fabrics align in subduction zones are two essential issues for clarifying material recycling between Earth’s interior and surface. Investigating seismic anisotropy is one of a few viable technologies that can directly answer these questions. However, the detailed anisotropic structure of subduction zones is still unclear. Under a general hexagonal symmetry anisotropy assumption, we develop a tomographic method to determine a high-resolution three-dimensional (3D) P wave anisotropic model of the Japan subduction zone by inverting 1,184,018 travel time data of local and teleseismic events. As a result, the 3D anisotropic structure in and around the dipping Pacific slab is firstly revealed. Our results show that slab deformation plays an important role in both mantle flow and intraslab fabric, and the widely observed trench-parallel anisotropy in the forearc is related to the intraslab deformation during the outer-rise yielding of the subducting plate.

scholarly journals Estimation of peak ground accelerations for Mexican subduction zone earthquakes using neural networks

2007 ◽  
Vol 46 (1) ◽  
pp. 51-63
Author(s):  
Silvia R. García ◽  
Miguel P. Romo ◽  
Juan M. Mayoral
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Epicentral Distance ◽  
Focal Depth ◽  
Neural Model ◽  
Attenuation Relations ◽  
Peak Ground Accelerations ◽  
Orthogonal Components ◽  
Subduction Zone Earthquakes ◽  
Mexican Subduction Zone

An extensive analysis of the strong ground motion Mexican data base was conducted using Soft Computing (SC) techniques. A Neural Network NN is used to estimate both orthogonal components of the horizontal (PGAh) and vertical (PGAv) peak ground accelerations measured at rock sites during Mexican subduction zone earthquakes. The work discusses the development, training, and testing of this neural model. Attenuation phenomenon was characterized in terms of magnitude, epicentral distance and focal depth. Neural approximators were used instead of traditional regression techniques due to their flexibility to deal with uncertainty and noise. NN predictions follow closely measured responses exhibiting forecasting capabilities better than those of most established attenuation relations for the Mexican subduction zone. Assessment of the NN, was also applied to subduction zones in Japan and North America. For the database used in this paper the NN and the-better-fitted- regression approach residuals are compared.

scholarly journals Ground Motion Prediction Equations for Malaysia Due to Subduction Zone Earthquakes in Sumatran Region

IEEE Access ◽  
2017 ◽  
Vol 5 ◽  
pp. 23920-23937
Author(s):  
M. S. Liew ◽  
Kamaluddeen Usman Danyaro ◽  
Mazlina Mohamad ◽  
Lim Eu Shawn ◽  
Aziz Aulov
Keyword(s):  
Subduction Zone ◽  
Ground Motion ◽  
Motion Prediction ◽  
Ground Motion Prediction Equations ◽  
Prediction Equations ◽  
Ground Motion Prediction ◽  
Subduction Zone Earthquakes

scholarly journals Dip angles of active faults from the surface to the seismogenic zone inferred from a 2D numerical analysis of visco-elasto-plastic models: a case study for the Osaka Plain

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hayami Nishiwaki ◽  
Takamoto Okudaira ◽  
Kazuhiko Ishii ◽  
Muneki Mitamura
Keyword(s):  
Urban Areas ◽  
Active Faults ◽  
Three Dimensional ◽  
Seismogenic Zone ◽  
Earthquake Ground Motion ◽  
Convex Curve ◽  
Seismic Reflection Profile ◽  
Geological Structures ◽  
Dimensional Distribution ◽  
Dip Angle

AbstractThe geometries (i.e., dip angles) of active faults from the surface to the seismogenic zone are the most important factors used to evaluate earthquake ground motion, which is crucial for seismic hazard assessments in urban areas. In Osaka, a metropolitan city in Japan, there are several active faults (e.g., the Uemachi and Ikoma faults), which are inferred from the topography, the attitude of active faults in surface trenches, the seismic reflection profile at shallow depths (less than 2 km), and the three-dimensional distribution of the Quaternary sedimentary layers. The Uemachi and Ikoma faults are N–S-striking fault systems with total lengths of 42 km and 38 km, respectively, with the former being located ~ 12 km west of the latter; however, the geometries of each of the active faults within the seismogenic zone are not clear. In this study, to examine the geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone, we analyze the development of the geological structures of sedimentary layers based on numerical simulations of a two-dimensional visco-elasto-plastic body under a horizontal compressive stress field, including preexisting high-strained weak zones (i.e., faults) and surface sedimentation processes, and evaluate the relationship between the observed geological structures of the Quaternary sediments (i.e., the Osaka Group) in the Osaka Plain and the model results. As a result, we propose geometries of the Uemachi and Ikoma faults from the surface to the seismogenic zone. When the friction coefficient of the faults is ~ 0.5, the dip angles of the Uemachi and Ikoma faults near the surface are ~ 30°–40° and the Uemachi fault has a downward convex curve at the bottom of the seismogenic zone, but does not converge to the Ikoma fault. Based on the analysis in this study, the dip angle of the Uemachi fault zone is estimated to be approximately 30°–40°, which is lower than that estimated in the previous studies. If the active fault has a low angle, the width of the fault plane is long, and thus the estimated seismic moment will be large.

scholarly journals Up the down escalator: the exhumation of (ultra)-high pressure terranes during on-going subduction

2012 ◽  
Vol 4 (1) ◽  
pp. 745-781 ◽  
Author(s):  
C. J. Warren
Keyword(s):  
High Pressure ◽  
Subduction Zone ◽  
Continental Crust ◽  
Subduction Zones ◽  
Crustal Material ◽  
Time And Space ◽  
Ultra High Pressure ◽  
Tectonic Environment ◽  
Tectonic Style ◽  
Weak Material

Abstract. The exhumation of high and ultra-high pressure rocks is ubiquitous in Phanerozoic orogens created during continental collisions, and is common in many ocean-ocean and ocean-continent subduction zone environments. Three different tectonic environments have previously been reported, which exhume deeply buried material by different mechanisms and at different rates. However it is becoming increasingly clear that no single mechanism dominates in any particular tectonic environment, and the mechanism may change in time and space within the same subduction zone. In order for buoyant continental crust to subduct, it must remain attached to a stronger and denser substrate, but in order to exhume, it must detach (and therefore at least locally weaken) and be initially buoyant. Denser oceanic crust subducts more readily than more buoyant continental crust but exhumation must be assisted by entrainment within more buoyant and weak material such as serpentinite or driven by the exhumation of structurally lower continental crustal material. Weakening mechanisms responsible for the detachment of crust at depth include strain, hydration, melting, grain size reduction and the development of foliation. These may act locally or may act on the bulk of the subducted material. Metamorphic reactions, metastability and the composition of the subducted crust all affect buoyancy and overall strength. Subduction zones change in style both in time and space, and exhumation mechanisms change to reflect the tectonic style and overall force regime within the subduction zone. Exhumation events may be transient and occur only once in a particular subduction zone or orogen, or may be more continuous or occur multiple times.

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