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1.
The central part of the Zagros Fold-Thrust Belt is characterized by a series of right-lateral and left-lateral transverse tear fault systems, some of them being ornamented by salt diapirs of the Late Precambrian–Early Cambrian Hormuz evaporitic series. Many deep-seated extensional faults, mainly along N–S and few along NW–SE and NE–SW, were formed or reactivated during the Late Precambrian–Early Cambrian and generated horsts and grabens. The extensional faults controlled deposition, distribution and thickness of the Hormuz series. Salt walls and diapirs initiated by the Early Paleozoic especially along the extensional faults. Long-term halokinesis gave rise to thin sedimentary cover above the salt diapirs and aggregated considerable volume of salt into the salt stocks. They created weak zones in the sedimentary cover, located approximately above the former and inactive deep-seated extensional faults. The N–S to NNE–SSW direction of tectonic shortening during the Neogene Zagros folding was sub-parallel with the strikes of the salt walls and rows of diapirs. Variations in thickness of the Hormuz series prepared differences in the basal friction on both sides of the Precambrian–Cambrian extensional faults, which facilitated the Zagros deformation front to advance faster wherever the salt layer was thicker. Consequently, a series of tear fault systems developed along the rows of salt diapirs approximately above the Precambrian–Cambrian extensional faults. Therefore, the present surface expressions of the tear fault systems developed within the sedimentary cover during the Zagros orogeny. Although the direction of the Zagros shortening could also potentially reactivate the basement faults as strike-slip structures, subsurface data and majority of the moderate-large earthquakes do not support basement involvement. This suggests that the tear fault systems are detached on top of the Hormuz series from the deep-seated Precambrian–Cambrian extensional faults in the basement. 相似文献
2.
Differences in fluids origin, creation of overpressure and migration are compared for end member Neogene fold and thrust environments: the deepwater region offshore Brunei (shale detachment), and the onshore, arid Central Basin of Iran (salt detachment). Variations in overpressure mechanism arise from a) the availability of water trapped in pore-space during early burial (deepwater marine environment vs arid, continental environment), and b) the depth/temperature at which mechanical compaction becomes a secondary effect and chemical processes start to dominate overpressure development. Chemical reactions associated with smectite rich mud rocks in Iran occur shallow (∼1900 m, smectite to illite transformation) causing load-transfer related (moderate) overpressures, whereas mechanical compaction and inflationary overpressures dominate smectite poor mud rocks offshore Brunei. The basal detachment in deepwater Brunei generally lies below temperatures of about 150 °C, where chemical processes and metagenesis are inferred to drive overpressure development. Overall the deepwater Brunei system is very water rich, and multiple opportunities for overpressure generation and fluid leakage have occurred throughout the growth of the anticlines. The result is a wide variety of fluid migration pathways and structures from deep to shallow levels (particularly mud dykes, sills, laccoliths, volcanoes and pipes, fluid escape pipes, crestal normal faults, thrust faults) and widespread inflationary-type overpressure. In the Central Basin the near surface environment is water limited. Mechanical and chemical compaction led to moderate overpressure development above the Upper Red Formation evaporites. Only below thick Early Miocene evaporites have near lithostatic overpressures developed in carbonates and marls affected by a wide range of overpressure mechanisms. Fluid leakage episodes across the evaporites have either been very few or absent in most areas. Locations where leakage can episodically occur (e.g. detaching thrusts, deep normal faults, salt welds) are sparse. However, in both Iran and Brunei crestal normal faults play an important role in the transmission of fluids in the upper regions of folds. 相似文献
3.
Fold-thrust belts formed above a ductile detachment typically contain detachment folds, whereas those formed above frictional detachments contain fault-related fold complexes, such as imbricate thrust systems. Analog models, using silica sand to represent sediments and silicone gel to represent salt were conducted to study the fold geometry, fold-fault relations, and sequential development of structures formed in each setting and at the boundaries between the two settings. The results showed a relatively thinner wedge above a ductile detachment, so that the deformation front propagated farther forward than that above a frictional detachment. The thrust front connects across the two settings with a significant change in position and a resulting change in orientation. The geometry of the deformation front is strongly controlled by that of the detachment boundary, so that an oblique detachment boundary results in an oblique thrust front in the transition zone. Modifications in the taper geometry also result from the presence of a frictional belt behind a ductile belt, the width of the ductile detachment which limits the location of the deformation front, and the lateral propagation of thrust faults between the two regimes. The experimental models can be used to explain observed geometries in natural examples of fold-thrust belts marked by transitions between frictional and ductile detachments. 相似文献
4.
Differences in fluids origin, creation of overpressure and migration are compared for end member Neogene fold and thrust environments: the deepwater region offshore Brunei (shale detachment), and the onshore, arid Central Basin of Iran (salt detachment). Variations in overpressure mechanism arise from a) the availability of water trapped in pore-space during early burial (deepwater marine environment vs arid, continental environment), and b) the depth/temperature at which mechanical compaction becomes a secondary effect and chemical processes start to dominate overpressure development. Chemical reactions associated with smectite rich mud rocks in Iran occur shallow (∼1900 m, smectite to illite transformation) causing load-transfer related (moderate) overpressures, whereas mechanical compaction and inflationary overpressures dominate smectite poor mud rocks offshore Brunei. The basal detachment in deepwater Brunei generally lies below temperatures of about 150 °C, where chemical processes and metagenesis are inferred to drive overpressure development. Overall the deepwater Brunei system is very water rich, and multiple opportunities for overpressure generation and fluid leakage have occurred throughout the growth of the anticlines. The result is a wide variety of fluid migration pathways and structures from deep to shallow levels (particularly mud dykes, sills, laccoliths, volcanoes and pipes, fluid escape pipes, crestal normal faults, thrust faults) and widespread inflationary-type overpressure. In the Central Basin the near surface environment is water limited. Mechanical and chemical compaction led to moderate overpressure development above the Upper Red Formation evaporites. Only below thick Early Miocene evaporites have near lithostatic overpressures developed in carbonates and marls affected by a wide range of overpressure mechanisms. Fluid leakage episodes across the evaporites have either been very few or absent in most areas. Locations where leakage can episodically occur (e.g. detaching thrusts, deep normal faults, salt welds) are sparse. However, in both Iran and Brunei crestal normal faults play an important role in the transmission of fluids in the upper regions of folds. 相似文献
5.
西非被动大陆边缘重力滑脱构造体系下的塑性构造 总被引：3，自引：0，他引：3
论述了西非被动大陆边缘深水环境下的重力滑脱构造体系中的塑性构造。研究发现塑性地层在整个西非被动大陆边缘都有分布,且盐岩塑性层主要分布在西非被动大陆边缘的西南部和西北部,发育层位为过渡期(J-K)构造层之内;中部尼日尔三角洲等塑性层主要为泥岩塑性层,发育层位为古近系和新近系。根据重力滑脱构造体系发育特征可划分为:以正断裂和塑性焊接构造为主的上部重力滑脱伸展构造、以底辟构造为主的中部重力滑脱底辟构造、以冲断裂、塑性褶皱和塑性冲断构造为主的下部重力滑脱冲断构造。根据塑性构造上覆地层的变形过程,塑性构造演化主要经历了后生变形期和同生变形期。塑性构造变形机制主要受基底掀斜作用和上覆地层的沉积速率控制。塑性构造中的底辟、褶皱、冲断及塑性焊接构造对油气成藏的控制作用依次减弱。 相似文献
6.
The Dezful Embayment is the most important fertile oil province of the Zagros Fold-Thrust Belt. It includes several incompetent strata as basal and intermediate décollement levels that play a significant role on the structural styles and hydrocarbon preservation. Based on the interpretation of seismic profiles, the influence of the Gachsaran Formation and the evaporitic Kalhur Member of the Asmari Formation on the geometry of deformation was investigated in different parts of the Dezful Embayment. Obtained results revealed that the thickness of the incompetent strata plays a crucial role in the formation and geometry of different types of fold structures (e.g. rounded, box, chevron, detachment fold) in the Dezful Embayment. There is a sharp difference between the geometry of surface and deep-seated structures due to the existence of thick intermediate décollements (e.g. Gachsaran and Kalhur) in the Dezful Embayment. Therefore, fault geometry and fold styles in upper and lower parts of these décollements are totally different. In addition, these incompetent strata act as a barrier level against the propagation of deep-seated faults into the overlying layers. Therefore, it seems that most of the faults exposed on the surface have originated from the upper décollement levels in the study area. 相似文献
7.
西非被动大陆边缘盐构造样式与成因机制 总被引：1，自引：0，他引：1
基于三维地震资料,对西非陆缘盐构造样式及分布特征进行了刻画,剖析了其形成演化机制与控制因素。西非陆缘盐上地层滑脱形成典型的薄皮构造,前缘发育挤压变形,后缘发育拉张变形,两者之间为过渡变形。拉张区发育白垩系盐筏、前盐筏、新近系盐筏等盐构造;过渡变形区以发育各种底辟构造为特征;挤压变形区主要发育侵位盐席构造。重力滑脱作用是被动陆缘盐构造发育过程中始终存在的驱动机制,重力扩展作用在大陆边缘成熟阶段作用明显,在陆缘演化早期并不突出。陆缘构造活动控制盐构造的形成,差异沉积负载作用影响着盐上地层滑移特征,而盐下底形对盐岩流动、盐上地层滑移速率及相关断裂体系的产生与沉积响应具有重要影响。 相似文献
8.
Late stage extensional character of the Samail Ophiolite, as inferred from structure within the Ibra-Dasir blocks, supports gravity-driven final emplacement for the ophiolite. This however, is not related to ‘collapse’ off ramp-related domal culminations as speculated in Late Cretaceous thrusting scenarios. Domal structures of the Oman Mountains are Tertiary structures as originally inferred by Glennie et al. (1974). Gravity-driven emplacement of the ophiolite is related to the rising NE-directed Saih Hatat fold-nappe, now preserved within the Saih Hatat window and offshore along the Batinah coast as the Saih Hatat axis. Ar-Ar geochronology indicates that the Saih Hatat antiformal fold-nappe development (76–70 Ma) was occurring at the time the ophiolite was being emplaced onto the margin between 70–80 Ma. Evidence for extension is shown by: (1) the truncation of fold structures in the ophiolite pseudostratigraphy by the approximately planar, late stage basal fault (previously referred to as the ‘Samail thrust’ and now as the Samail detachment fault), (2) faults within the ophiolite cutting down section (e.g., Jabal Dimh fault), and (3) by the presence of both high angle and low angle normal faults, particularly in the metamorphic sole rocks at Wadi Tayin. Kinematic analysis of the high angle fault pairs in the metamorphic sole at Wadi Tayin indicates N–S pull-apart. These features of the Samail Ophiolite, along with similar features in the Bay of Islands Ophiolite in New Foundland, suggest that final stages of ophiolite obduction onto continental margins must involve extensional emplacement as a thin (< 5 km) sheet. This emplacement is accompanied by further thinning of the ophiolite sheet with internal development of both low and high angle normal faults. 相似文献
9.
Controls on turbidite sand deposition during gravity-driven extension of a passive margin: examples from Miocene sediments in Block 4, Angola 总被引：1，自引：0，他引：1
In recent years, exploration of the Lower Congo Basin in Angola has focused on the Neogene turbidite sand play of the Malembo Formation. Gravity tectonics has played an important role during deposition of the Malembo Formation and has imparted a well-documented structural style to the post-rift sediments. An oceanward transition from thin-skinned extension through mobile salt and eventually to thin-skinned compressional structures characterises the post-rift sediments. There has been little discussion, however, regarding the influence of these structures on the deposition of the Malembo Formation turbidite sands. Block 4 lies at the southern margin of the Lower Congo Basin and is dominated by the thin-skinned extensional structural style. Using a multidisciplinary approach we trace the post-rift structural and stratigraphic evolution of this block to study the structural controls on Neogene turbidite sand deposition.In the Lower Congo Basin the transition from terrestrial rift basin to fully marine passive margin is recorded by late Aptian evaporites of the Loeme Formation. Extension of the overlying post-rift sequences has occurred where the Loeme Formation has been utilised as a detachment surface for extensional faults. Since the late Cretaceous, the passive margin sediments have moved down-slope on the Loeme detachment. This history of gravity-driven extension is recorded in the post-rift sediments of Block 4. Extension commenced in the Albian in the east of the block and migrated westwards with time. In the west, the extension occurred mainly in the Miocene and generated allochthonous fault blocks or “rafts”, separated by deep grabens. The Miocene extension occurred in two main phases with contrasting slip vectors; in the early Miocene the extension vector was to the west, switching to southwest-directed extension in the late Miocene. Early Miocene faults and half-grabens trend north–south whereas late Miocene structures trend northwest–southeast. The contrast in slip vectors between these two phases emphasises the differences in driving mechanisms: the early Miocene faulting was driven by basinward tilting of the passive margin, but gravity loading due to sedimentary progradation is considered the main driver for the late Miocene extension. The geological evolution of the late Miocene grabens is consistent with southwest-directed extension due to southwest progradation of the Congo fan.High-resolution biostratigraphic data identifies the turbidite sands in Block 4 as early Miocene (17.5–15.5 Ma) and late Miocene (10.5–5.5 Ma) in age. Deposition of these sands occurred during the two main phases of gravity-driven extension. Conditions of low sedimentation rates relative to high fault displacement rates were prevalent in the early Miocene. Seafloor depressions were generated in the hangingwalls of the main extensional faults, ultimately leading to capture of the turbidity currents. Lower Miocene turbidite sand bodies therefore trend north–south, parallel to the active faults. Cross-faults and relay ramps created local topographic highs capable of deflecting turbidite flows within the half grabens. Flow-stripping of turbidity currents across these features caused preferential deposition of sands across, and adjacent to, the highs. Turbidite sands deposited in the early part of the late Miocene were influenced by both the old north–south fault trends and by the new northwest–southeast fault trends. By latest Miocene times turbidite channels crosscut the active northwest–southeast-trending faults. These latest Miocene faults had limited potential to capture turbidity currents because the associated hangingwall grabens were rapidly filled as pro-delta sediments of the Congo fan prograded across the area from the northeast. 相似文献
10.
GLORIA and SeaMARC II sea-floor images of offshore Western Samoa reveal large-scale mass movements, volcanism, and structural modification. These processes are driven by hot-spot mantle diapirism and nearby plate subduction. Debris avalanche deposits extend from the island slope onto the adjacent abyssal plains, covering at least 20,000 km2. Sediment flows occur in sheets up to 30 km wide; slump structures are common on steep slopes. Volcanic cones and lava sheets are evident on lower slopes and abyssal plains. Major volcanic rift zones on the island of Savaii continue offshore. Subduction-induced flexure has produced intense tensional fracturing on the outer wall of the Tonga Trench. 相似文献
11.
琼东南盆地断裂构造与成因机制 总被引：24，自引：0，他引：24
琼东南盆地断裂较为发育,主要发育NE、近EW和NW向的三组断裂,其中NE向和近EW向断裂是主要的控盆断裂。盆地早期发育主要受基底先存断裂的控制,形成了众多裂陷构造;晚期主要受热沉降作用控制,断裂不太发育,对沉积的控制作用较弱,从而使盆地具有典型的裂陷盆地和双层结构特征。琼东南盆地受到太平洋俯冲后撤、印藏碰撞和南海张开等多期构造的作用,盆地的裂陷期可以分为两阶段:始新世—早渐新世的整体强张裂期,晚渐新世—早中新世的弱张裂期。 相似文献
12.
Stuart Hardy 《Marine and Petroleum Geology》2011,28(5):966-972
A discrete element model is used to investigate progressive cover deformation above a steep (70°), basement normal fault. The cover materials are homogenous with frictional material behavior. In the model shown here both normal and reverse faults in the cover accommodate displacement on the underlying basement fault. The earliest faults are curved, reverse faults which propagate upwards from the basement fault tip into the proto hanging wall. These are replaced, progressively towards the footwall, by subvertical to steep normal faults and finally by a normal fault which dips at an angle predicted by Mohr-Coulomb theory. Thus, most early, secondary structures are located in the hanging-wall of the final, through-going, fault. This structural evolution produces an asymmetric, triangular zone of deformation above the basement fault tip which superficially resembles that associated with trishear; however, its progressive development is quite different. Results also emphasize that the occurrence of reverse faults in extensional settings is not diagnostic of inversion. 相似文献
13.
莱州湾凹陷位于渤海南部海域,为中生界基底之上发育的新生代半地堑.郯庐断裂带分东西两支穿过莱州湾凹陷东部,在新生代盖层中表现出渤海最复杂最典型的为NNE向的右旋走滑断裂特征.其中东支断裂在渐新世以后活动强烈,发育多条NNE向走滑断层及NE向伴生断层组成的复杂断裂带.走滑断裂带内断层展布符合右旋单剪作用下的脆性走滑剪切模式,地震方差切片存在右旋运动拖拽断裂证据.通过对主断裂活动期次分析表明,研究区主要有三期大的构造活动,同时形成了三期构造反转.应力分布的局域性导致了形变特征的差异性,产生了褶皱、挤压反转、掀斜断块、花状构造等典型的构造类型.研究区首次利用三维地震资料对本区构造特征进行了分析,研究认为走滑活动形成了良好的构造背景、优越的油源及运移等成藏条件,具有较大的油气勘探潜力. 相似文献
14.
A discrete-element model is used to investigate the manner in which deformation and fault activity change in space and time during the development of a doubly vergent thrust wedge in the upper crust. Deformation is a result of shortening at a subduction slot in the base of the model, a configuration which produces a dynamic backstop within the cohesionless, frictional cover material. A series of experiments with differing basal (decollement) friction are performed. The distinct manners in which thrust wedges grow, and the variability of fault development and activity in space and time, are then examined. Both predicted large-scale wedge geometries and individual fault-fold structures are similar to those observed in sandbox models, and show the complex manner in which shortening is accommodated and localized during the development of the thrust wedge. When compared to a sandbox model with similar boundary conditions, model results are strikingly similar. In all cases, deformation initiates above the subduction slot with the formation of an axial zone; the wedge is then developed by displacement on a retro-wedge thrust and propagation of deformation into the pro-wedge region. Models with low coefficients of basal friction typically develop wide, shallow wedges with distributed, spaced deformation and rather symmetric, box-like structures; whereas those with high coefficients of basal friction develop narrower, steeper wedges, consisting of a series of stacked, pro-wedge thrust sheets, and a high-displacement retro-wedge thrust. In general, fault initiation and linkage is extremely complex in our models, with several smaller faults operating until linkage occurs to form a major through-going structure. Of particular interest is the observation that many of the faults do not develop at the basal decollement and propagate upwards through the cover but rather initiate at high levels in the cover and propagate/link downwards with other, deeper structures. Results also indicate the utility of the discrete-element approach in modelling large-displacement, complex deformation of geological materials. 相似文献
15.
The SW Iberian margin developed as a passive margin during Mesozoic times and was later inverted during the mainly Cenozoic Alpine orogeny. The initial syn-rift deposits include a Lower Jurassic evaporite unit of variable thickness. In the onshore, this unit is observed to thicken basinward (i.e., southward), in fault-controlled depocenters, and salt-related structures are only present in areas of thick initial evaporites. In the offshore, multiple salt-structures cored by the Lower Jurassic evaporites are interpreted on seismic reflection data and from exploratory drilling. Offshore salt structures include the allochthonous Esperança Salt Nappe, which extends over an area roughly 40 × 60 km. The abundance of salt-related structures and their geometry is observed to be controlled by the distribution of evaporite facies, which is in turn controlled by the structure of rift-related faulting. This paper presents a comprehensive study of salt tectonics over the entire onshore and offshore SW Iberian passive margin (southern Portugal and Gulf of Cadiz), covering all aspects from initial evaporite composition and thickness to the evolution of salt-related structures through Mesozoic extension and Cenozoic basin inversion. 相似文献
16.
丽水—椒江凹陷是一个中新生代断陷盆地,断裂构造组成了盆地内的主要构造样式。通过对区域断层剖面组合和平面展布特征的研究,识别出8种类型的断层剖面组合形式,在平面上划分了12个断裂系统区。总体来说本区构造具有东西分带、南北分块的特征,即断裂系统沿北东—南西方向成条带状分布,凹陷南部以地堑式组合为主,北部以地垒式为主。区域断裂系统的演变显示凹陷南北基底基岩存在差异,而且基底发育北西—南东向的断层,从而导致凹陷南部构造活动较北部强。 相似文献
17.
Growth faults in gravity-driven extensional provinces are dominated by coast-parallel trends, but coast-perpendicular (transverse) trends are far less documented. The Clemente–Tomas fault in the inner Texas shelf has corrugations that are transverse to the fault and that plunge downdip. A large (8500 km2), high-quality, 3D seismic survey allows a uniquely encompassing perspective into hanging-wall deformation above this corrugated fault surface. Synextensional strata in the hanging wall are folded into alternating transverse ridges and synclines, typically spaced 10 km apart. Forward modelling in dip profiles of an extensional fault having three ramps produces ramp basin-rollover pairs that compare with the seismically revealed ridges and synclines. As they translated down the undulose fault plane, ramp basins and rollovers were juxtaposed along strike, forming the hanging-wall ridges and synclines observed offshore Texas. Fault-surface corrugations correlate broadly with footwall structure. We infer that corrugations on the Clemente–Tomas fault formed by evacuation of an allochthonous salt canopy emplaced in the late Eocene to early Oligocene. Early salt evacuation (Oligocene) created an undulose topography that influenced incipient Clemente-Tomas fault segments as they merged to form an inherently undulose fault. Late salt evacuation (early Miocene) further deformed this fault surface. 相似文献
18.
伶仃洋南部断裂构造特征 总被引：2，自引：0，他引：2
利用综合地球物理调查资料研究了伶仃洋南部断裂构造的位置、延伸方向和产状特征。结果表明,在伶仃洋南部的断裂是陆域断裂在海域的延伸,以基岩断裂为主,少数断裂影响到第四系沉积物,并表现出分段活动性。海域NE—ENE向断裂与两侧陆域的NE—ENE向断裂连接在一起,构成一条完整的NE—ENE向断裂构造体系。NW向断裂活动时代晚于NE—ENE向断裂,其右行走滑运动将NE—ENE向断裂截切和错移。形成这一构造格局的主要动力来自新生代以来南海的拉张作用以及澳洲板块南北向的推挤作用。 相似文献
19.
Integrated tectono-stratigraphic interpretation at MC-118 using 3D seismic, well logs and biostratigraphy reveals an area dominated by allochthonous salt and its related structures. OCS-Block MC-118 is located 130 km southeast of New Orleans on the Gulf of Mexico middle slope in ∼2600 ft of water.The area is divided into three domains based on their structural styles: (1) a western domain consisting of a basinward-dipping normal fault family and associated strata; (2) a central domain composed of a landward-plunging diapiric salt tongue canopy and associated salt welds, two flanking NE–SW trending salt-withdrawal mini-basins, and a crestal fault family; and (3) an eastern domain comprised of basinward/landward-dipping normal and listric normal fault families with their associated rollovers. These structural domains are genetically-and-kinematically related to the salt structure and extend beyond MC-118 boundaries. The salt structure is postulated to have evolved mostly passive, with punctuated active episodes, and by lateral spreading. This is part of a larger regional structure, eastern Gulf of Mexico, which involves some amalgamation between small-scale salt canopies and salt diapirs although collectively they appear mostly disconnected.A Pliocene (3.13–4.95 Ma) third-order genetic stratigraphic sequence, the focus of this study, is as much as ∼3600 ft thick within the mini-basins and contains: muddy mass transport complexes; sandy slope fans; muddy turbidites and condensed sections; and transitional facies flanking the salt structure that collectively have ponded and wedged external geometries. Mass transport complexes and muddy turbidites and condensed sections make most of the studied genetic sequence in a mud-dominated deltaic setting eastern Gulf of Mexico.Facies kinematic indicators and a matching number of genetic sequences accounted on the sea level chart support a eustatically driven mini-basin sedimentation. Nonetheless salt still plays a role in sedimentation (secondary/minor) by slumping generated during passive/active salt diapiric evolution. 相似文献
20.
Salt rollers are low-amplitude deflections of the upper surface of a salt layer which occur below zones of normal faulting in the overlying sediments. They are widely recognised in association with tilted blocks or listric fault rollover systems. Laboratory experiments on brittle ductile models made of sand and silicone putty are used to study the modes of development, the external shape and the internal structures of these salt rollers. Firstly, flow and strain patterns within décollement zones are described. Finite strain combines layer-perpendicular shortening and layer-parallel shear. Additional flow cells within rollers perturb the laminar flow of the décollement, inducing a passive folding of planar markers. The same type of flow and strain patterns occur in all types of rollers, ranging from those occurring below tilted blocks to those associated with growth faults. Finally, an analysis of roller shapes through the measurement of aspect ratios and asymmetry ratios shows that the shapes of tilted blocks rollers and growth fault rollers—which differ at initiation tend to converge with increasing deformation. 相似文献