Structure of the present-day velocity field of the crust in the area of the Central-Asian GPS network

Кузиков, С. И.; Мухамедиев, Ш. А.

doi:10.1134/s1069351310070037

Cited by 31 publications

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“…Попытка непосредственного выявления блоч-ной структуры в поле современных горизонталь-ных скоростей по данным Центрально-Азиатской GPS-сети [Mukhamediev et al, 2006;Kuzikov, Mukhamediev, 2010] показала, что упрощенная альтерна-тива «дискретность-сплошность», представленная упомянутыми выше точками зрения, а также мне-ние о возможном способе их сближения нуждаются, по меньшей степени, в серьезной корректировке, если речь идет о современных движениях. Выде-ленные односвязные квазижесткие 2D домены, существующие в настоящий момент и испытыва-ющие поступательные и вращательные движения, не контактируют между собой по границам («раз-ломам»), а разделены относительно широкими зо-нами повышенных деформаций.…”

Section: особенности деформирования геосредыunclassified

“…Пространственная корреляция между этими зонами и геологическими разломами отсутствует, хотя существует взаимо-связь между их угловыми распределениями и направлениями сдвигов по ним. В геометрии и ки-нематике выявленных зон прослеживается скры-тая регулярность, отражающая динамическое воз-действие Индийской плиты [Kuzikov, Mukhamediev, 2010;.…”

Section: особенности деформирования геосредыunclassified

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On Discrete Structure of Geologic Medium and Continual Approach to Modeling Its Movements

Мухамедиев

2016

Geodin. tektonofiz.

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This paper discusses the structure of a geologic medium represented by accessible lithified rocks and provides an overview of methods used to describe its movements. Two basic opinions are considered in the framework of the discussion: (1) an initially homogeneous and continuous geologic medium acquires the structure composed of blocks in the process of the geologic medium's deformation/destruction/degradation, and (2) a geologic medium is composed of blocks (and often has hierarchic, active, energy-saturated features), and the continuity model is thus not valid for describing the geologic medium's deformation. Proponents of the first point of view actively apply the standard or modified continuum model of a solid deformed body (SDB) in estimations of the stress-strain state, but the input parameters of this model do not contain any information on discreteness in principle. Authors who support the second opinion, either explicitly or implicitly assume that the block structure of the geologic medium, which is detectable by geological methods, makes a direct and unambiguous impact on all other mechanical properties of the geologic medium and, above all, on the nature of its movements.Based on results obtained by interpreting the data collected in our long-term field studies of rock fracturing, mathematical processing of GPS-measurements, and theoretical models, we agree with the concept of the geologic medium's block structure, but argue that the geologic block-structure property is not acquired but congenital. Regarding sedimentary rocks, it means that the discrete structure has been already embodied in the rock before sediment lithification, regardless of the intensity of macroscopic deformations. A discrete structure is the form of the geologic medium existence and a cause of the congenital anisotropy of the geologic medium's strength characteristics. Due to subsequent deformation of the geologic medium, some elements of the structure can be manifested more clearly, and the structure itself can become more complex due to secondary effects. At the same time, the structure of geologic blocks is not directly manifested in the spatial and temporal features of the recent movements in the geologic medium. However, it is not an obstacle to developing continuum models of such movements in the same way as, for instance, the adequacy of the continuum general theory of relativity is not denied in view of the discrete-hierarchical structure of the Universe.The key requirements to a model include its applicability, testability, confirmability/deniability of its predictions in the investigated space-time scale, and compliance with conservation laws. This paper briefly discusses the most important aspects of the continuum approach based on the concept of an effective continuous medium and, above all, the Cauchy continuum model, envisaging that the dynamic response of the medium in spatial descriptions is given only by the Cauchy symmetric stress tensor (T). In more general continuum models of the medium (such as mom...

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Section: особенности деформирования геосредыunclassified

On Discrete Structure of Geologic Medium and Continual Approach to Modeling Its Movements

Мухамедиев

2016

Geodin. tektonofiz.

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“…2. Данные 323 пунктов GPS-наблюдений на Центрально-Азиатском полигоне в 1995-2005 гг., обозначенных точками [Kuzikov, Mukhamediev, 2010]. a -вектора смещений всего полигона, в целом; b -дифференцированные вращения блоков как жестких образований, в каждом блоке выявленные по таким совокупностям наблюдательных пунктов, имеющих нулевые горизонтальные перемещения друг относительно друга.…”

Section: Rotation Waves In the Geomedium Composed Of Rotating Blocksunclassified

Wave moment geodynamics

Vikulin

Tveritinova

Ivanchin³

2012

Acta Geophys.

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Abstract:The geomedium block concept envisages that stresses in the medium composed of rotating blocks have torque and thus predetermine the medium's energy capacity (in terms of [Ponomarev, 2008]). The present paper describes the wave nature of the global geodynamic process taking place in the medium characterized by the existence of slow and fast rotation strain waves that are classified as a new type of waves. Movements may also occur as rheid, superplastic and/or superfluid motions and facilitate the formation of vortex geological structures in the geomedium.Our analysis of data on almost 800 strong volcanic eruptions shows that the magma chamber's thickness is generally small, about 0.5 km, and this value is constant, independent of the volcanic process and predetermined by properties of the crust. A new magma chamber model is based on the idea of 'thermal explosion'/'self-acceleration' manifested by intensive plastic movements along boundaries between the blocks in conditions of the low thermal conductivity of the geomedium. It is shown that if the solid rock in the magma chamber is overheated above its melting point, high stresses may occur in the surrounding area, and their elastic energy may amount to 10 15 joules per 1 km 3 of the overheated solid rock. In view of such stresses, it is possible to consider the interaction between volcano's magma chambers as the migration of volcanic activity along the volcanic arc and provide an explanation of the interaction between volcanic activity and seismicity within the adjacent parallel arcs.The thin overheated interlayer/magma chamber concept may be valid for the entire Earth's crust. In our hypothesis, properties of the Moho are determined by the phase transition from the block structure of the crust to the nonblock structure of the upper mantle.Key words: geodynamics, force moment, rotational waves, rheid flow, gravitational waves. Аннотация: В работе развивается концепция блоковой геосреды применительно к геодинамическому (сей-смическому и вулканическому) процессу. Работу, в целом, можно представить в виде четырех частей: введе-ния, шести разделов, кратко описывающих разработанную ранее автором ротационную модель сейсмотекто-нического процесса, трех разделов, посвященных развитию блоковой концепции применительно к вулкани-ческому процессу, и обсуждения результатов. Recommended by S.I. ShermanВо введении на примере анализа исследований, проводимых в течение последних десятилетий сотрудни-ками Института земной коры СО РАН, показывается, что концепция тектонофизического процесса Байкаль-ской рифтовой зоны, разрабатываемая в рамках разломной тектоники на региональном уровне, не позволяет видеть всю картину в целом. Региональные концепции существенным образом опираются на представления GEODYNAMICS & TECTONOPHYSICS P U B L I S H E D B Y T H E I N S T I T U T E O F T H E E A R T H ' S C R U S T S I B E R I A N B R A N C H O F R U S S I A N A C A D E M Y O F S C I E N C E S R e c e n t G e o d y n a m i c s 345А.V. Vikulin: Geodynamics as wave dynamics… о разломах, ...

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“…Результа-ты этих исследований представлены в работах [Zubovich, 2001;Meade, Hager, 2001;Kuzikov, Mukhamediev, 2010;Kostyuk, 2008]. В работах [Zubovich, 2001;Zubovich et al, 2001] была рассчитана дивергенция поля скоростей, что не давало информации о на-правлениях главных осей тензора деформации.…”

Section: Introductionunclassified

“…В работах [Zubovich, 2001;Zubovich et al, 2001] была рассчитана дивергенция поля скоростей, что не давало информации о на-правлениях главных осей тензора деформации. В работах [Meade, Hager, 2001, Kuzikov, Mukhamediev, 2010 были предложены блоковые модели, причем конфигурация квазижестких блоков в них принци-пиально отличается, что пока не позволяет гово-рить о возможности получения надежной блоковой модели для описания современных деформаций Северного Тянь-Шаня. В данной работе был ис-пользован подход, подобный использованному в работе [Kostyuk, 2008], позволяющий получить тен-зор скорости деформации в окрестности любой точки земной коры, что дает информацию о на-правлении главных осей деформации, ее скорости по каждой из этих осей и позволяет рассчитать скорость относительного изменения площади и максимально возможную величину сдвиговых де-формаций.…”

Section: Introductionunclassified

Comparison of Crustal Deformation Rates Estimated From Seismic and GPS Data on the Bishkek Geodynamic Polygon

Сычева¹,

Мансуров²

2017

Geodin. tektonofiz.

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Abstract:The Bishkek geodynamic polygon (BGP,.5° N -73-77° E) is located within the central segment of the North Tien Shan seismic zone, in the junction zone of the Tien Shan orogene and the Turan plate ( Fig. 1). In the entire modern structure of Tien Shan lengthwise zones of shearing (with both right-and left-lateral strike-slip faults) are observed, thus Tien Shan can be considered as a transpression zone. Our study aimed at comparing deformation values estimated for the BGP territory from the seismic and GPS data. The modern stress-strain state of the study area was determined from the focal mechanisms of 1287 earthquakes that occurred in the period from 1994 to 2015. The study area was divided into cells with a radius of 0.2° (~20 km). The cell centers were in the nodes of the grid with a spacing of 0.1° (~10 km). A tensor of a seismotectonic deformation (STD) rate within a cell was calculated as a sum of seismic moment tensors normalized for time, volume and shear modulus, assuming that STD is similar at different scale levels. The STD field is shown in Figure 4 at the background given by the deformation intensity pattern. Figure 6 shows the scatter of the sums of the strain rate tensor's horizontal components estimated from the seismic data. The modern crustal movements were estimated from the geodetic measurements performed on the Central Asian GPS Network. Using the crustal movement velocities for 90 sites in the study area, the deformation processes in the crust were modeled based on the linear part of the Taylor expansion of the point's-velocity-versus-its-radius-vector function. Then the velocity gradient tensors were estimated for the grid nodes with a spacing of 8.3 km. To estimate tensor's value in every single grid node a system of linear algebraic equations was solved by the weighted least-squares method. The weight of an observation point decreased with an increasing distance to such point, so that the inhomogeneity of the deformation field could be taken into account. From the velocity gradient tensors we calculate the strain rate tensors (Fig. 5) and then the rate of changes of the area (meterage) ∆ (Fig. 7). A comparison of Figures 4 and 5 shows a general coincidence between the directions of compression/shortening axes estimated from the seismic and GPS data. On average, the STD intensity is by two to three orders lower than the deformation intensity assessed from the GPS data. It can be explained by the fact that the horizontal components of the total deformation amounts visible in the GPS data are actually the sums of aseismic and coseismic components, and the deviator part of coseismic component was considered as STD. Comparing the fields of the sums of the strain rate tensor's horizontal components from the seismic data (Fig. 6) and the GPS data (Fig. 7) reveals an inconsistency for the Suusamyr depression: the GPS data shows a considerable crustal shortening in the horizontal plane, while the seismic data is indicative of a shear deformation. In the central part of the junction zone of...

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Structure of the present-day velocity field of the crust in the area of the Central-Asian GPS network

Cited by 31 publications

References 17 publications

On Discrete Structure of Geologic Medium and Continual Approach to Modeling Its Movements

On Discrete Structure of Geologic Medium and Continual Approach to Modeling Its Movements

Wave moment geodynamics

Comparison of Crustal Deformation Rates Estimated From Seismic and GPS Data on the Bishkek Geodynamic Polygon

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