Two-Element Keyboard-Block Model Of Megathrust Earthquakes Generation For Central Kurils

The strongest subduction earthquakes (M&#8805;8) lead to the release of the huge amount of elastic stresses accumulated over hundreds or even thousands of years. Prediction of such earthquakes, causing significant socio-economic and environmental damage, is one of the most important and urgent tasks of geophysics.To date, significant advances have been made in the field of earthquake prediction using models based on the concept of a continuous geophysical medium that ruptured coseismically along the main fault. As an alternative, models are proposed that take into account the fault-block structure of the continental margin, confirmed by seismological and oceanographic studies. In our study, we consider one of such models - a keyboard-block model (single-element) which combines the ideas of possible synchronous destruction of several adjacent asperities, mutual slip along a plane with variable friction depending on velocity, and subsequent healing of destructed portions of the medium under high-pressure conditions. This concept made it possible to simulate the displacement of surface points of frontal seismogenic blocks at all stages of the seismic cycle.GNSS observations in subduction regions are carried out mostly on islands situated on the rear massif far from the seismogenic blocks. Strong multidirectional motion registered on GNSS stations during the seismic cycle, as well as seismological and geological data, clearly indicate that the rear part of the arc also has a complex structure and is divided into separate segments by large faults rooted into the contact zone of interacting lithospheric plates. We made a generalization (double-element) of the original model to consider the discontinuity of not only the frontal but also the rear part of the island arc.We compared the earth's surface displacements during the seismic cycle in the Central Kurils, obtained within the framework of the continuous model, as well as the single-element and two-element keyboard models, to establish the influence of various configurations of the fault-block structure of the continental margin on the seismic cycle. We constructed the continuous model on the basis of our slip distribution model for the 2006 Simushir earthquake which indicates the interplate coupling patches prior to this earthquake.This study was supported by the Russian Science Foundation (project 20&#8211;17-00140).

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The role of the fault-block structure of the continental margin in the generation of the strongest subduction earthquakes

10.5194/egusphere-egu2020-8854 ◽

2020 ◽

Author(s):

Irina Vladimirova ◽

Yury Gabsatarov ◽

Dmitry Alekseev ◽

Leopold Lobkovsky

Keyword(s):

Continental Margin ◽

Block Structure ◽

Geodetic Data ◽

Seismic Cycle ◽

Subduction Earthquakes ◽

Fault Block ◽

Proposed Model ◽

Geodynamic Processes ◽

Rupture Mode ◽

Large Earthquakes

Modern seismotectonic studies are aimed at obtaining a self-consistent explanation of fault zone heterogeneity, the rupture process, recurrence times and rupture mode of large earthquake sequences. In subduction regions large earthquakes are often characterized by very long source zones and complex long-term postseismic processes following the coseismic release of accumulated elastic stresses. A set of mechanical models was proposed to describe the generation of strongest earthquakes based on the idea of the synchronous failure of several adjacent asperities.In this study we propose a model which is based on verified numerical schemes, which allows us to quantitatively characterize the process of generation of strong earthquakes. The model takes into account the fault-block structure of the continental margin and combined the ideas of a possible synchronous destruction of several adjacent asperities, mutual sliding along a fault plane with a variable coefficient of friction and subsequent healing of medium defects under high pressure conditions.The applicability of the proposed model is shown by the example of the recent seismic history of the Kuril subduction zone. Kuril island arc is one of the most tectonically active regions of the world due to very high plate convergence rate. Heterogeneities in the mechanical coupling of the interplate interface in this region lead to the formation of the block structure of the continental margin, which is confirmed by various geological and seismological studies.GPS observations recorded at different stages of seismic cycle related to the 2006&#8211;2007 Simushir earthquakes allow us to model geodynamic processes of slow strain accumulation and its rapid release during the earthquake and the subsequent posteseismic process. We use parameters describing the regional tectonic structure and rheology obtained from the inversion of geodetic data to construct a 2D model of generation of large earthquakes in central Kurils. Analysis of paleoseismic data on dates and rupture characteristics of previous major earthquakes shows a good agreement between the modeled and observed seismic cycle features. The predicted horizontal displacements of the seismogenic block at the coseismic stage are consistent with satellite geodetic data recorded during the 2006 Simushir earthquake.The proposed model provides new insights into the geodynamic processes controlling the occurrence of strong subduction earthquakes.

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The role of the fault-block structure of the continental margin in the generation of the strongest subduction earthquakes

10.1002/essoar.10502997.1 ◽

2020 ◽

Author(s):

Irina Vladimirova ◽

Yury Gabsatarov ◽

Dmitry Alexeev ◽

Leopold Lobkovsky

Keyword(s):

Continental Margin ◽

Block Structure ◽

Subduction Earthquakes ◽

Fault Block

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Stratigraphy of amethyst geode-bearing lavas and fault-block structures of the Entre Rios mining district, Paraná volcanic province, southern Brazil

Anais da Academia Brasileira de Ciências ◽

10.1590/0001-37652014201120004 ◽

2013 ◽

Vol 86 (1) ◽

pp. 187-198 ◽

Cited By ~ 6

Author(s):

LÉO A. HARTMANN ◽

LUCAS M. ANTUNES ◽

LEONARDO M. ROSENSTENGEL

Keyword(s):

Block Structure ◽

Underground Mines ◽

Mining District ◽

Volcanic Province ◽

Fault Block ◽

River Bed ◽

World Class ◽

Entre Rios ◽

Block Structures

The Entre Rios mining district produces a large volume of amethyst geodes in underground mines and is part of the world class deposits in the Paraná volcanic province of South America. Two producing basalt flows are numbered 4 and 5 in the lava stratigraphy. A total of seven basalt flows and one rhyodacite flow are present in the district. At the base of the stratigraphy, beginning at the Chapecó river bed, two basalt flows are Esmeralda, low-Ti type. The third flow in the sequence is a rhyodacite, Chapecó type, Guarapuava subtype. Above the rhyodacite flow, four basalt flows are Pitanga, high-Ti type including the two mineralized flows; only the topmost basalt in the stratigraphy is a Paranapanema, intermediate-Ti type. Each individual flow is uniquely identified from its geochemical and gamma-spectrometric properties. The study of several sections in the district allowed for the identification of a fault-block structure. Blocks are elongated NW and the block on the west side of the fault was downthrown. This important structural characterization of the mining district will have significant consequences in the search for new amethyst geode deposits and in the understanding of the evolution of the Paraná volcanic province.

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Fault-block structure and state of stress in the Earth’s crust of the Gusinoozersky Basin and the adjacent territory, western Transbaikal region

Geotectonics ◽

10.1134/s0016852109010051 ◽

2009 ◽

Vol 43 (1) ◽

pp. 67-84 ◽

Cited By ~ 4

Author(s):

O. V. Lunina ◽

A. S. Gladkov

Keyword(s):

Block Structure ◽

Earth’S Crust ◽

Transbaikal Region ◽

Adjacent Territory ◽

State Of Stress ◽

Fault Block ◽

Earth's Crust

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Rift systems of the East Siberian basin, Arctic region

10.5194/egusphere-egu2020-8551 ◽

2020 ◽

Author(s):

Nickolay Zhukov ◽

Anatoly Nikishin ◽

Eugene Petrov

Keyword(s):

Continental Margin ◽

Large Scale ◽

Block Structure ◽

Sedimentary Basins ◽

Rift System ◽

Northwestern Part ◽

Gravitational Fields ◽

Stage Of Development ◽

East Siberian Sea ◽

Seismic Lines

The growing interest of geoscientists to the Eastern Arctic shelf is caused one of the most important problems of the present time &#8211; the creation of a tectonic model for assessing the hydrocarbon potential of the Eastern Arctic basins. In this time, over the past decade, the study of the East Siberian sea seismic lines have increased. Now, we operated a new seismic data, the interpretation of which gives the key to understanding the structure of the East Siberian continental margin.This paper presents an analysis of the tectonic structure and geological history of the shelf of the East Siberian continental margin based on the interpretation of seismic lines in conjunction with geological information.The modern ideas of the East Arctic rift tectonic evolution and formation of sedimentary basins over the entire East Siberian shelf resulted from the large-scale tectonic and magmatism events took place and the intense rifting or stretching phase widespread the entire shelf in the Albian-Aptian.The East Siberian basin includes the main structural elements, formed in a postcollisional destructive stage of development &#8211; the New Siberian rift, the De Long uplift, the Zhokhov Foredeep basin, the Melville trough, the Baranov rise, the Pegtymel trough, the Shelagskoe rise.The New Siberian rift is located between the elevations of the New Siberian Islands and the archipelago De Long. Rift extends in a southeast direction from the East-Anisin Trough deflection to the Islands of Faddeev Island and New Siberia Islands. The New Siberian rift is a bright negative structural element and clearly stands out on the maps of the anomalous magnetic and gravitational fields, contrasting with the positive anomalies of surrounding rises and ridges.De Long Plateau is a large positive structure. The uplift boundaries and internal structure are clearly visible in the gravitational and magnetic fields. The magnetic anomaly expressed in the De long, it is a typical for the areas of development of volcanogenic formations and basalts trap magmatism.The East Siberian Rift System located from the northwestern part of the De long Plateau to the eastern part of the North Chukchi basin. System includes the Melville trough in the southern part of the East Siberian Sea. The reflector packages on seismic lines in the De Long Plateau and The East Siberian Rift System indicate that continental rifting occurred over the mantle plum.The length of the Melville trough is a 350-370 km; with a width of 100-150 km. Trough is the symmetrical deflection consists of two narrow rifts separated by a rise.The eastern branch of the rift system of the Melville trough joins the Baranov rise. The Baranov rise has a block structure with the geometry of which is similar to the block structure of the De-Long Plateau.The Dremkhed trough is a deep rift structure transitional between the East Siberian and North Chukchi basins, the thickness of the sedimentary cover in central part of section is 7000 ms.The study was funded by RFBR project - 18-05-70011.

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