Academic literature on the topic 'Subduction-zone interplate coupling'

Colombia is tectonically active, and several large earthquakes have ruptured the Colombia-Ecuador subduction zone (CESZ) during the last century. Among them, the Colombia-Ecuador earthquake in 1906 (Mw 8.4) and the Tumaco earthquake in 1979 (Mw 8.3) generated destructive tsunamis. Therefore, it is important to characterize the seismic rupture processes and their relation with interplate coupling along the CESZ. We searched for repeating earthquakes by performing waveform similarity analysis. Cross correlation (CC) values were computed between earthquake pairs with hypocenter differences of less than 50 km that were located in the northern CESZ (1°–4°N) and that occurred from June 1993 to February 2018. We used broadband and short-period seismic waveform data from the Servicio Geológico Colombiano (SGC) seismic network. A CC threshold value of 0.90 was used to identify the waveform similarity and select repeating earthquakes. We found repeating earthquakes distributed near the trench and the coast. Our estimated repeating earthquakes near the trench suggest that the interplate coupling in this region is low. This is in clear constrast to the occurrence of a large slip in the 1906 Colombia-Ecuador earthquake along the trench in the southern part of the CESZ, and suggests that rupture modes are different between the northern and southern parts of CESZ near the trench.

The geometry of supposed coupling zones in the Kamchatka subduction zoneis determined by the earthquake size distribution based on earlier revealed relationship between its shape and rate of inelastic deformations. In the areas of higher aseismic slip, a break of linearity in earthquake size distribution is observed owing to the deficit of large earthquakes. Zones of higher coupling between the oceanic and continental plates are characterized by an excess of large earthquakes and an inverse bend in the earthquake size distribution. The mapping results of the bend value agree with the coupling zones distinguished from satellite geodetic data and inversion of marigrams.

SUMMARY The Northern Chilean subduction zone is characterized by long-term subduction erosion with very little sediment input at the trench and the lack of an accretionary prism. Here, multichannel seismic reflection (MCS) data were acquired as part of the CINCA (Crustal Investigations off- and onshore Nazca Plate/Central Andes) project in 1995. These lines cover among others the central part of the MW 8.1 Iquique earthquake rupture zone before the earthquake occurred on 1 April 2014. We have re-processed one of the lines crossing the updip parts of this earthquake at 19°40′S, close to its hypocentre. After careful data processing and data enhancement, we applied a coherency-based pre-stack depth migration algorithm, yielding a detailed depth image. The resulting depth image shows the subduction interface prior to the Iquique megathrust earthquake down to a depth of approximately 16 km and gives detailed insight into the characteristics of the seismogenic coupling zone. We found significantly varying interplate reflectivity along the plate interface which we interpret to be caused by the comparably strong reflectivity of subducted fluid-rich sediments within the grabens and half-grabens that are predominant in this area due to the subduction-related bending of the oceanic plate. No evidence was found for a subducted seamount associated to the Iquique Ridge along the slab interface at this latitude as interpreted earlier from the same data set. By comparing relocated fore- and aftershock seismicity of the Iquique earthquake with the resulting depth image, we can divide the continental wedge into two domains. First, a frontal unit beneath the lower slope with several eastward dipping back-rotated splay faults but no seismicity in the upper plate as well as along the plate interface. Secondly, a landward unit beneath the middle slope with differing reflectivity that shows significant seismicity in the upper plate as well as along the plate interface. Both units are separated by a large eastward dipping mega splay fault, the root zone of which shows diffuse seismicity, both in the upper plate and at the interface. The identification of a well-defined nearly aseismic frontal unit sheds new light on the interplate locking beneath the lower continental slope and its controls.

AbstractThis paper presents a synthetic view of the geodynamic evolution of the Zagros orogen within the frame of the Arabia–Eurasia collision. The Zagros orogen and the Iranian plateau preserve a record of the long-standing convergence history between Eurasia and Arabia across the Neo-Tethys, from subduction/obduction processes to present-day collision (from ~ 150 to 0 Ma). We herein combine the results obtained on several geodynamic issues, namely the location of the oceanic suture zone, the age of oceanic closure and collision, the magmatic and geochemical evolution of the Eurasian upper plate during convergence (as testified by the successive Sanandaj–Sirjan, Kermanshah and Urumieh–Dokhtar magmatic arcs), the P–T–t history of the few Zagros blueschists, the convergence characteristics across the Neo-Tethys (kinematic velocities, tomographic constraints, subduction zones and obduction processes), together with a survey of recent results gathered by others. We provide lithospheric-scale reconstructions of the Zagros orogen from ~ 150 to 0 Ma across two SW–NE transects. The evolution of the Zagros orogen is also compared to those of the nearby Turkish and Himalayan orogens. In our geotectonic scenario for the Zagros convergence, we outline three main periods/regimes: (1) the Mid to Late Cretaceous (115–85 Ma) corresponds to a distinctive period of perturbation of subduction processes and interplate mechanical coupling marked by blueschist exhumation and upper-plate fragmentation, (2) the Paleocene–Eocene (60–40 Ma) witnesses slab break-off, major shifts in arc magmatism and distributed extension within the upper plate, and (3) from the Oligocene onwards (~ 30–0 Ma), collision develops with a progressive SW migration of deformation and topographic build-up (Sanandaj–Sirjan Zone: 20–15 Ma, High Zagros: ~12–8 Ma; Simply Folded Belt: 5–0 Ma) and with partial slab tear at depths (~10 Ma to present). Our reconstructions underline the key role played by subduction throughout the whole convergence history. We finally stress that such a long-lasting subduction system with changing boundary conditions also makes the Zagros orogen an ideal natural laboratory for subduction processes.

Northeast Japan experienced an approximately constant, compressional deformation during the last 5 million years resulting from the steady subduction of the Pacific plate. Because the direction of the maximum compression axis is approximately perpendicular to the strike of the island arc, 2-D finite-element modeling can be used to examine the deformation over time of the island-arc lithosphere. The model geometry is based on geophysical and geological data, and each model run requires an assumed rheology and interplate coupling. Novel to our modeling is the ability to include erosion/deposition loading and the creation of strike-slip faults, based on a dynamically-applied fracture criterion. The criterion for acceptability is how well a model matches observed present-day topography, gravity, and seismicity patterns. Results given below are for models that satisfy this criterion. The long-term effective elastic thickness is 10 km in the inner arc, increasing to about 50 km near the trench. The effective elastic thickness in the inner arc is therefore much smaller than the about 30 km short-term elastic thickness estimated from seismological data. The viscosity of the lower crust is on the order of 1022 Pa s or less. The strength of interplate coupling off Sanriku is about two to four times greater than off Miyagi, and there is about twice as strong a coupling at greater depths. The relative strength of coupling correlates well with the observed interplate seismicity. Hence the inferred weaker coupling off Miyagi indicates a lack of seismogenic potential -- a low probability for large earthquakes in that region, not just a long return cycle. The same modeling procedure was also applied to southwest Japan. The viscosity of the lower crust is not more than 1021 Pa s, and the elas tic thickness is about 10 km. The calculated strength of interplate coupling for southwest Japan is about 1.5 times greater than for the off-Sanriku region in northeast Japan, which correlates well with the fact that there have been great (M>8) earthquakes in the Nankai Trough region, but none that large in the off-Sanriku region.
Ph. D.

La plupart des grands séismes se produit sur les frontières de plaques tectoniques en subduction mais la segmentation sismique au long des zones de subduction reste encore mal comprise. Pour mieux comprendre cette segmentation sismique, j’ai traité, analysé et interprété des données de bathymétrie multifaisceaux et de sismique réflexion de haute résolution. Ces données ont été acquises durant la campagne géophysique MegaTera. Celle-ci a levé la région où la Zone de Fracture Investigator (IFZ en anglais), constituée de longues rides sous-marines, rentre dans la zone de subduction de Sumatra central. Les résultats de l’interprétation montrent que la subduction de ce groupe de quatre rides a un impact considérable sur la morphologie du prisme d’accrétion, notamment des failles normales et décrochantes, ainsi que des chevauchements, conduisant sous l’effet de l’érosion au développement de systèmes de canaux et de bassins complexes. Le relief des rides IFZ a soulevé les sédiments de l’avant-arc, produisant aussi de la subsidence à la suite de la subduction des rides. Les parties frontales des rides en subduction ont favorisé le maintien des chevauchements sur de longues durées, alors que le décollement passe horizontalement par les sédiments situés au-dessus des deux rides voisines. J’ai également réalisé des modèles 3D géodynamiques numériques afin d’étudier les effets de la subduction oblique de rides sur l’évolution de la contrainte persistante et les types de déformation permanente de l’avant-arc. Finalement, J’ai analysé et comparé les résultats des modèles numériques avec l’interprétation du plancher océanique et les structures situées sous la surface du fond marin. Les résultats intégrés indiquent que les rides IFZ en subduction ont généré une déformation du prisme d’accrétion et un comportement de la contrainte qui sont hétérogènes au long du prisme. Par conséquent, la subduction des rides IFZ pourrait favoriser l’hétérogénéité du couplage interplaque, agissant comme une frontière de segmentation sismique et représentant donc un candidat plausible pour arrêter la propagation du grand tremblement de terre de 2005 Nias-Simeulue, Mw 8.7
Major earthquakes occur mainly on subduction plate boundaries, but what causes the along strike earthquake segmentation remains poorly understood. To understand earthquake segmentation, I have processed, analysed and interpreted high-resolution seismic reflection and multibeam bathymetry data acquired during the MegaTera experiment of 2015. The MegaTera survey covered an area where the Investigator Fracture Zone (IFZ), a linear group of long ridges, impinges the trench along the central Sumatra subduction zone. The interpretation results show the subduction of these four groups of ridges has a considerable impact on the accretionary wedge morphology, including strike-slip and normal faulting, along with thrusts, leading to the development of complex channel systems and basins, and hence erosion. The relief of IFZ ridges has uplifted the forearc sediments, creating subsidence in the wake of subducting ridges. Frontal parts of the subducting ridges have created long-lived thrusts, whereas the décollement horizontally passes through the sedimentary sequences on the top of two neighbouring ridges. Additionally, I have performed 3-D numerical geodynamic models to study the effects of oblique subduction of ridges on the persistent stress evolution and the permanent forearc deformation patterns. Finally, I have analysed and compared the numerical experiments to the interpretation of the seafloor and subsurface features. The overall results indicate the subducting IFZ create heterogeneous wedge deformation and stress behaviour along the accretionary prism. Hence, the subduction of the IFZ might promote a heterogeneous inter-plate coupling, acting as a segment boundary and being a proper candidate for having stopped the south-eastward propagation of the 2005 Mw 8.7 Nias-Simeulue earthquake