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21.
Crustal motion and deformation in Greece from a decade of GPS measurements, 1993–2003 总被引:1,自引:1,他引:0
The Hellenic plate boundary region, located in the collision zone between the Nubian/Arabian and Eurasian lithospheric plates, is one of the seismo-tectonically most active areas of Europe. During the last 15 years, GPS measurements have been used to determine the crustal motion in the area of Greece with the aim to better understand the geodynamical processes of this region. An extended reoccupation network covering whole Greece has been measured periodically in numerous GPS campaigns since the late eighties, and a continuous GPS network has been operated in the region of the Ionian Sea since 1995. In this paper, we present a new detailed high-quality solution of continuous and campaign-type measurements acquired between 1993 and 2003. During the GPS processing, a special effort was made to obtain consistent results with highest possible accuracies and reliabilities. Data of 54 mainly European IGS and EUREF sites were included in the GPS processing in order to obtain results which are internally consistent with the European kinematic field and order to allow for a regional interpretation. After an overview of the results of the IGS/EUREF sites, the results from more than 80 stations in Greece are presented in terms of velocities, time series, trajectories and strain rates. Previous geodetic, geological and seismological findings are generally confirmed and substantially refined. New important results include the observation of deformation zones to the north and to the south of the North Aegean Trough and in the West Hellenic arc region, arc-parallel extension of about 19 mm/yr along the Hellenic arc, and compression between the Ionian islands and the Greek mainland. Due to continuous long-term observations of 4–8 years, it was possible to extract height changes from the GPS time series. In Greece, we observe a differential subsidence of the order of 2 mm/yr between the northern and central Ionian islands across the Kefalonia fault zone. The differential subsidence of the central Ionian islands with respect to the northwestern Greek mainland amounts to 4 mm/yr. 相似文献
22.
Four types of soft-sediment folds of distinct geometry can be recognized in the upper part of the Talchir Formation (Lower Permian) of Jharia Basin, India. These folds, on systematic examination, indicate some events of progressive deformation. Experimental study reveals that if a layered stack of clay and overlying sand is allowed to flow slowly down a slope, differential velocity due to viscosity contrast leads to the deformation of the rheologic interface. The sharp planar contact gradually becomes wavy leading to the development of round-hinged folds involving sediments adjacent to it. With the advancement of the flow these folds gradually become overturned with the rotation of the axial plane in the direction of flow. Computer simulation suggests that progressive deformation of these folds by simple shearing may lead to the formation of tight isoclinal folds, which on dislocation along intrastratal normal faults may lead to the development of rootless isoclinal folds. The sheath folds observed in the studied section also indicate accentuation of the curved hinge due to simple shearing. The spatial distribution of these fold types in conjunction with the inferred direction of progressive deformation indicate basinward translation of the slump slice. If the same stack of sediments rapidly flows down the slope, the waveform generated at the interface quickly breaks in the form of roll-up recumbent fold due to Kelvin–Helmholtz instability. 相似文献
23.
S. Amir Reza Beyabanaki Roozbeh Geraili Mikola Kianoosh Hatami 《Computers and Geotechnics》2008,35(3):346-356
This paper presents a new contact calculating algorithm for contacts between two polyhedra with planar boundaries in the three-dimensional discontinuous deformation analysis (3-D DDA). In this algorithm, all six type contacts in 3-D (vertex-to-face, vertex-to-edge, vertex-to-vertex, face-to-face, edge-to-edge, and edge-to-face) are simply transformed into the form of point-to-face contacts. The presented algorithm is a simple and efficient method and it can be easily coded into a computer program. In this paper, formulations of normal contact, shear contact and frictional force submatrices based on the new method are derived and the algorithm has been programmed in VC++. Examples are provided to demonstrate the new contact rule between two blocks. 相似文献
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无外加流体、350℃和差异应力条件下硫化物再活化实验研究 总被引:1,自引:0,他引:1
红透山块状硫化物矿石主要成分为黄铁矿、磁黄铁矿、黄铜矿、闪锌矿和石英、角闪石、黑云母等脉石矿物。将此矿石烘干后作为试料置于岩石三轴应力试验机,在13h内将轴压、围压和温度分步升至1276MPa、414MPa和350℃,然后在空气中自然冷却至室温。实验产物中黄铁矿、石英、长石等以脆性碎裂为主,而磁黄铁矿、黄铜矿、闪锌矿和云母等以塑性变形为主。再活化的黄铜矿、磁黄铁矿和少量闪锌矿呈脉和网脉穿插黄铁矿碎斑。实验结果表明,即使没有外来流体加入.构造动力作用所导致的流体包裹体破坏所释出的流体,就足以使成矿物质发生活化转移和再活化。 相似文献
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Deformation Patterns of an Accretionary Wedge in the Transition Zone from Subduction to Collision Offshore Southwestern Taiwan 总被引:1,自引:0,他引:1
Char-Shine Liu Benoit Deffontaines Chia-Yu Lu Serge Lallemand 《Marine Geophysical Researches》2004,25(1-2):123-137
Swath bathymetry data and seismic reflection profiles have been used to investigate details of the deformation pattern in the area offshore southwestern Taiwan where the Luzon subduction complex encroaches on the passive Chinese continental margin. Distinctive fold-and-thrust structures of the convergent zone and horst-and-graben structures of the passive margin are separated by a deformation front that extends NNW-ward from the eastern edge of the Manila Trench to the foot of the continental slope. This deformation front gradually turns into a NNE–SSW trending direction across the continental slope and the Kaoping Shelf, and connects to the frontal thrusts of the mountain belt on land Taiwan. However, the complex Penghu submarine canyon system blurs the exact location of the deformation front and nature of many morphotectonic features offshore SW Taiwan. We suggest that the deformation front offshore SW Taiwan does not appear as a simple structural line, but is characterized by a series of N–S trending folds and thrusts that terminate sequentially in an en-echelon pattern across the passive Chinese continental slope. A number of NE–SW trending lineaments cut across the fold-and-thrust structures of the frontal accretionary wedge and exhibit prominent dextral displacement indicative of the lateral expulsion of SW Taiwan. One of the prominent lineaments, named the Yung-An lineament, forms the southeastern boundary of the upper part of the Penghu submarine canyon, and has conspicuous influence over the drainage pattern of the canyon 相似文献
29.
1 .IntroductionTheBohaiGulfisinfestedbyiceinthewholewinter,andoffshorestructuresthereexperiencenotonlywind ,waves ,currentsandearthquake ,butalsoiceloadswhicharecomplicatedbecauseofthedynamicinteractionbetweenicesheetsandstructures.Duanetal.( 2 0 0 0 )hadacomprehensivere viewofthelatestadvancesonice inducedvibration ,fatigueandfractureofoffshorestructures ,payingmuchattentiontothedifferencesinicebreakingmodeanddynamicsofstructuresindifferentice in festedwaters .Theypresentedcriticallythelates… 相似文献
30.
大陆岩石圈在张裂和分离时的变形模式 总被引:4,自引:0,他引:4
姚伯初 《海洋地质与第四纪地质》2002,22(3):59-67
通过对南海南北共轭边缘地壳剖面的对比研究,发现大陆岩石圈的物理性质是分层的:上、中地壳呈脆性,下地壳表现出塑性,而岩石圈上地幔则仍呈脆性。因此,在它受张性应力场作用时,其变形和破裂分离方式也是分层进行的:上、中地壳能发生犁式断裂,产生的断块沿断面转动在地表产生一系列半地堑,并使地壳厚度减薄;如拉张应力继续作用时,上、中地壳将沿犁式断裂被拉开,从而形成上、下板块边缘,并彼此分开。下地壳则发生塑性变形,使地壳厚度减薄,并最终将其拉断。岩石圈上地幔亦可产生陡倾断裂,形成的断块沿断面转动亦使其厚度减薄,并最终沿陡倾断裂被拉断。这就是我们称之为岩石圈变形和破裂分 离时的分层变形及分层破裂分离模式。 相似文献