Relationships between deformation and morphology of forearc wedges and earthquake ruptures

2021 ◽  
Author(s):  
Nadaya Cubas
Keyword(s):  
Subduction Zones ◽  
Permanent Deformation ◽  
Seismic Cycle ◽  
Earthquake Rupture ◽  
Earthquake Ruptures ◽  
Mechanical Modelling ◽  
Seismic Behaviors ◽  
Deformation Patterns ◽  
Rupture Properties ◽  
Effective Friction

<p>Over the last decade, we have accumulated evidence that, along subduction zones, a significant part of the seismic cycle deformation is permanently acquired by the medium and reflects the variation of rupture properties along the megathrust. Assuming a persistence of the megathrust segmentation over several hundred thousand years, this permanent deformation and the forearc topography could thus reveal the mechanics of the megathrust. Numerous recent studies have also shown that the megathrust effective friction appears to differ significantly between aseismic or seismic areas. From mechanical modelling, I will first discuss how such differences in effective friction are significant enough to induce wedge segments with varying morphologies and deformation patterns. I will present examples from different subduction zones characterized by either erosive or accretionary wedges, and by different seismic behaviors. Secondly, I will present how this long-lived deformation can in turn control earthquake ruptures. I will show, that along the Chilean subduction zone, all recent mega-earthquakes are surrounded by basal erosion and underplating. Therefore, the deformation and morphology of forearcs would both be partly linked to the megathrust rupture properties and should be used in a more systematic manner to improve earthquake rupture prediction.</p>

Linking geodynamic subduction models to self-consistent 3D dynamic earthquake rupture and tsunami simulations

2020 ◽  
Author(s):  
Sara Aniko Wirp ◽  
Alice-Agnes Gabriel ◽  
Elizabeth H. Madden ◽  
Iris van Zelst ◽  
Lukas Krenz ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Surface Boundary ◽  
Seismic Cycle ◽  
Earthquake Rupture ◽  
Dynamic Rupture ◽  
Cycle Model ◽  
Earthquake Dynamics ◽  
Rupture Mode ◽  
Fully Coupled ◽  
Tsunami Models

<p>3D imaging reveals striking along-trench structural variations of subduction zones world-wide (e.g., Han et al, JGR 2018). Subduction zones include basins, sediments, splay and back-thrusting faults that evolve over a large time span due to tectonic processes, and may crucially affect earthquake dynamics and tsunami genesis. Such features should be taken into account for realistic hazard assessment. Numerical modeling bridges time scales of millions of years of subduction evolution to seconds governing dynamic earthquake rupture, as well as spatial scales of hundreds of kilometers of megathrust geometry to meters of an earthquake rupture front.</p><p>Recently, an innovative framework linking long-term geodynamic subduction and seismic cycle models to dynamic rupture models of the earthquake process and seismic wave propagation at coseismic timescales was presented (van Zelst et al., JGR 2019). This workflow was extended in a simple test case to link the 2D seismic cycle model to a three-dimensional earthquake rupture mode, which was then linked to a tsunami model  (Madden et al., EarthArxiv, doi:10.31223/osf.io/rzvn2). Here, we couple a 2D seismic cycle model to 3D earthquake and tsunami models and assess the geophysical aspects of this coupling. We extract all 2D material properties, stresses and the strength of the megathrust, and its geometry, from the seismic cycling model at a time step right before a typical megathrust event to use as initial conditions for the 3D dynamic rupture models. We explore the effects of along-arc variations of megathrust curvature, sediment content, and closeness to failure of the wedge on earthquake dynamics by studying the effects on slip, rupture velocity, stress drop and seafloor deformation.</p><p>In a next step, the dynamic seafloor displacements are linked to tsunami simulations that use depth-integrated (hydrostatic) shallow water equations. This approach efficiently models wave propagations and large-scale horizontal flows. We also present novel, fully coupled 3D dynamic rupture-tsunami simulations (Krenz et al., AGU19; Abrahams et al., AGU19; Lotto and Dunham et al., 2015, Computational Geosciences) which solve simultaneously for the solid earth and ocean response, taking gravity into account via a modified free surface boundary condition.</p><p>Earthquake rupture modeling and the fully-coupled tsunami modeling utilize SeisSol (www.seissol.org), a flagship code of the ChEESE project (www.cheese-coe.eu). SeisSol is an open source software package using unstructured tetrahedral meshes that are optimally suited for the complex geometries of subduction zones. The here presented links between geodynamic subduction and seismic cycling model with earthquake dynamics and tsunami models better account for the complexity of subduction zones and help evaluate the effects of along arc heterogeneities on earthquake and tsunami behavior and advance physics-based assessments of earthquake-tsunami hazards.</p>

Build seismic cycle balance deformation with InSAR in Northen Chile

2020 ◽  
Author(s):  
Lauriane Bayle ◽  
Romain Jolivet ◽  
Nadaya Cubas ◽  
Laetitia Le Pourhiet
Keyword(s):  
Time Series ◽  
Subduction Zones ◽  
Permanent Deformation ◽  
Seismic Cycle ◽  
Seismic Displacement ◽  
Uplift Rates ◽  
Short And Long Term ◽  
Period Data ◽  
Illapel Earthquake

<p>Lauriane Baylé (1), Romain Jolivet (2), Nadaya Cubas (1) and Laetitia Le</p><p>Pourhiet (1)</p><p>(1) Institut des Sciences de la Terre de Paris, UMR 7193, UPMC UniversitéParis 6, CNRS, Paris,</p><p>France</p><p>(2) Laboratoire de Géologie, Département de Géosciences, École Normale Supérieure, CNRS UMR 8538,</p><p>PSL ResearchUniversity, Paris, France</p><p>Recent studies have pointed out to a discrepancy between the short- and long-</p><p>term deformation of overriding plates in subduction zones. This led to debates</p><p>about when and how permanent deformation is acquired. This contradiction</p><p>has notably been observed along the Central Andes Subduction Zone, where</p><p>the coast subsides during and shortly after major earthquakes while a coastal</p><p>uplift with rates ranging between 0.1 and 0.3 mm/yr has been inferred the</p><p>last 4000 ky. For instance, during the 15th September 2015 Mw 8.3 Illapel</p><p>earthquake the geodetics (GPS and InSAR) data show a coastal subsidence</p><p>along the line-of-sight of 20 cm in InSAR.</p><p>To reconcile the seemingly contradictory observations, we here propose to</p><p>provide a seismic cycle uplift balance by constrainning inter-, co- and post-</p><p>seismic vertical velocities from InSAR time series. The study focuses on La</p><p>Serena peninsula (71.3°W, 30°S, Chile) along which the Illapel earthquake</p><p>occurred and for which long-term uplift rates have been provided by previous</p><p>geomorphological studies.</p><p>To build this seismic cycle balance, we use InSAR data (Sentinel-1) acqui-</p><p>red between the September 15, 2015 and January 19, 2019. The time series</p><p>for the ascendant orbite is calculated and the accumulated vertical displace-</p><p>ment extracted providing co- and post-seismic displacement. The co-seismic</p><p>displacement are similar to those previously obtain. To constrain the displa-</p><p>cement during the inter-seismic period, data on both sides of the peninsula</p><p>are used. In that respect, we aim determining when, during the seismic cycle,</p><p>and where, along the coast, the uplift occurs.</p><p>The deduced time series will then be confronted to numerical modelling</p><p>to provide the short- and long-term mechanics reproducing the short- and</p><p>long-term observations.</p>

scholarly journals Earthquake ruptures and topography controlled by plate interface deformation

2021 ◽  
Author(s):  
Nadaya Cubas ◽  
Philippe Agard ◽  
Roxane Tissandier
Keyword(s):  
Subduction Zones ◽  
Permanent Deformation ◽  
Mechanical Analysis ◽  
Global Navigation Satellite Systems ◽  
Northern Chile ◽  
Southern Chile ◽  
Plate Interface ◽  
Interface Deformation ◽  
Slip Deficit ◽  
Earthquake Ruptures

Abstract. What controls the location and segmentation of mega-earthquakes in subduction zones is a long-standing problem in earth sciences. Prediction of earthquake ruptures mostly relies on interplate coupling models based on Global Navigation Satellite Systems providing patterns of slip deficit between tectonic plates. We here investigate if and how the seismic and aseismic patches revealed by these models relate to the distribution of deformation along the plate interface, i.e. basal erosion and/or underplating. From a mechanical analysis of the topography applied along the Chilean subduction zone, we show that extensive plate interface deformation takes place along most of the margin. We show that basal erosion occurs preferentially at 15 km depth while underplating does at 35 ± 10 and 60 ± 5 km depth, in agreement with P-T conditions of recovered underplated material, expected pore pressures, and spatial distribution of marine terraces and uplift rates. Along southern Chile, large sediment input favors shallow accretion and underplating of subducted sediments, while along northern Chile, extensive basal erosion provides material for the underplating. We then show that all major earthquakes of southern Chile are limited along their down-dip end by underplating while, along northern Chile, they are surrounded by both basal erosion and underplating. Segments with heterogeneously distributed deformation largely coincide with lateral earthquake terminations. We therefore propose that long-lived plate interface deformation promotes stress build-up and leads to earthquake nucleation. Earthquakes then propagate along fault planes shielded from this long-lived permanent deformation, and are finally stopped by segments of heterogeneously distributed deformation. Slip deficit patterns and earthquake segmentation therefore reflect the along-dip and along-strike distribution of the plate interface deformation. Topography acts as a mirror of distributed plate interface deformation and should be studied systematically to improve the prediction of earthquake ruptures.

Seismo-hydro-mechanical modelling of the seismic cycle: Methodology and implications for subduction zone seismicity

2020 ◽  
Vol 791 ◽  
pp. 228504 ◽  
Author(s):  
Claudio Petrini ◽  
Taras Gerya ◽  
Viktoriya Yarushina ◽  
Ylona van Dinther ◽  
James Connolly ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Seismic Cycle ◽  
Mechanical Modelling

Modeling the Interaction between Slow Slip Events and Earthquake Ruptures in the Nicoya Peninsula, Costa Rica. 

2021 ◽  
Author(s):  
Lise Alalouf ◽  
Yajing Liu
Keyword(s):  
Costa Rica ◽  
Subduction Zones ◽  
Computation Time ◽  
Seismogenic Zone ◽  
Model Parameters ◽  
Slow Slip ◽  
Coseismic Slip ◽  
Slow Slip Events ◽  
Megathrust Earthquakes ◽  
Earthquake Ruptures

<p>Subduction zones are where the largest earthquakes occur. In the past few decades, scientists have also discovered the presence of episodic aseismic slip, including slow slip events (SSEs), along most of the subduction zones. However, it is still unclear how these SSEs can influence megathrust earthquake ruptures. The Costa Rica subduction zone is a particularly interesting area because a SSE was recorded 6 months before the 2012 Mw7.6 earthquake in the Nicoya Peninsula, suggesting a potential stress transfer from the SSE to the earthquake slip zone. SSEs beneath the Nicoya Peninsula were also recorded both updip and downdip the seismogenic zone, making it a unique area to study the complex interaction between SSEs and earthquakes.</p><p>As most of the shallow SSEs were recorded around the Nicoya Peninsula, we chose to start using a 1D planar fault embedded in a homogeneous elastic half-space, with different dipping angles following several geometric profiles of the subduction fault beneath the Nicoya Peninsula section of the Costa Rica margin. This 1D modelling study allows us to better investigate the interaction between shallow and deep SSEs and megathrust earthquakes with high numerical resolution and relatively short computation time. The model provides information on the long-term seismic history by reproducing the different stages of the seismic cycle (interseismic slip, shallow and deep episodic slow slip, and coseismic slip).</p><p>We study the influence of the variation of numerical parameters and frictional properties on the recurrence interval, maximum slip velocity and cumulative slip of SSEs (both shallow and deep) and earthquakes and their interaction with each other. We then compare our results with GPS and seismic observations (i.e. cumulative slip, characteristic duration, moment rate, depth and size of the rupture, equivalent magnitude) to identify an optimal set of model parameters to understand the interaction between various modes of subduction fault deformation.</p>

Geometric controls on megathrust earthquakes

2020 ◽  
Vol 222 (2) ◽  
pp. 1270-1282
Author(s):  
Steven M Plescia ◽  
Gavin P Hayes
Keyword(s):  
Subduction Zone ◽  
Subduction Zones ◽  
Earthquake Hazard ◽  
Earthquake Rupture ◽  
Primary Control ◽  
Slab Geometry ◽  
Megathrust Earthquakes ◽  
Maximum Earthquake Magnitude ◽  
Maximum Earthquake

SUMMARY The role of subduction zone geometry in the nucleation and propagation of great-sized earthquake ruptures is an important topic for earthquake hazard, since knowing how big an earthquake can be on a given fault is fundamentally important. Past studies have shown subducting bathymetric features (e.g. ridges, fracture zones, seamount chains) may arrest a propagating rupture. Other studies have correlated the occurrence of great-sized earthquakes with flat megathrusts and homogenous stresses over large distances. It remains unclear, however, how subduction zone geometry and the potential for great-sized earthquakes (M 8+) are quantifiably linked—or indeed whether they can be. Here, we examine the potential role of subduction zone geometry in limiting earthquake rupture by mapping the planarity of seismogenic zones in the Slab2 subduction zone geometry database. We build from the observation that historical great-sized earthquakes have preferentially occurred where the surrounding megathrust is broadly planar, and we use this relationship to search for geometrically similar features elsewhere in subduction zones worldwide. Assuming geometry exerts a primary control on earthquake propagation and termination, we estimate the potential size distribution of large (M 7+) earthquakes and the maximum earthquake magnitude along global subduction faults based on geometrical features alone. Our results suggest that most subduction zones are capable of hosting great-sized earthquakes over much of their area. Many bathymetric features previously identified as barriers are indistinguishable from the surrounding megathrust from the perspective of slab curvature, meaning that they either do not play an important role in arresting earthquake rupture or that their influence on slab geometry at depth is not resolvable at the spatial scale of our subduction zone geometry models.

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

<p>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 Pāpaku 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.</p>

scholarly journals Time-dependent geoid anomalies at subduction zones due to the seismic cycle

2017 ◽  
Vol 212 (1) ◽  
pp. 139-150 ◽  
Author(s):  
G Cambiotti ◽  
R Sabadini ◽  
D A Yuen
Keyword(s):  
Subduction Zones ◽  
Time Dependent ◽  
Seismic Cycle ◽  
Geoid Anomalies

scholarly journals Seismoturbidite record as preserved at core sites at the Cascadia and Sumatra–Andaman subduction zones

2013 ◽  
Vol 13 (4) ◽  
pp. 833-867 ◽  
Author(s):  
J. R. Patton ◽  
C. Goldfinger ◽  
A. E. Morey ◽  
C. Romsos ◽  
B. Black ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Low Frequency ◽  
Turbidity Current ◽  
Turbidity Currents ◽  
Earthquake Rupture ◽  
Glacial Cycle ◽  
Basin Effects ◽  
Frequency Components ◽  
Temporal And Spatial ◽  
Current Flows

Abstract. Turbidite deposition along slope and trench settings is evaluated for the Cascadia and Sumatra–Andaman subduction zones. Source proximity, basin effects, turbidity current flow path, temporal and spatial earthquake rupture, hydrodynamics, and topography all likely play roles in the deposition of the turbidites as evidenced by the vertical structure of the final deposits. Channel systems tend to promote low-frequency components of the content of the current over longer distances, while more proximal slope basins and base-of-slope apron fan settings result in a turbidite structure that is likely influenced by local physiography and other factors. Cascadia's margin is dominated by glacial cycle constructed pathways which promote turbidity current flows for large distances. Sumatra margin pathways do not inherit these antecedent sedimentary systems, so turbidity currents are more localized.

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