Kinematics-Based Mathematical Model for Deforming Thrust Wedges     

Matty Mookerjee  Gautam Mitra 《Mathematical Geosciences》2008,40(3):249-275

Given the wealth of data concerning the kinematics of deforming fold-thrust belts (FTBs), first-order generalizations about how the major strain components vary within a deforming thrust wedges are considered. These generally observed strain patterns are used to constrain a general, kinematics-based, FTB-wedge model. We considered five strain components within a deforming thrust sheet: (1) thrust-parallel simple shear, (2) horizontal contractional strain, (3) thrust-normal reaction strain, (4) gravitational strain, and (5) a lateral confining boundary condition. After making assumptions about how these strain components vary within a model FTB-wedge, the incremental deformation matrix can be calculated for any given point within the deforming wedge. Thus, the material path of a given marker can be determined and an initially spherical marker’s strain path can be calculated as it moves through the deforming wedge. Furthermore, by illustrating various kinematic parameters of many initially spherical markers (for example, Flinn’s k-value, incremental octahedral shear strain, transport-perpendicular stretch), we have assembled representations of the kinematic properties of the entire model wedge. By including a flat-ramp-flat fault surface geometry for the model wedge, we are able to examine the kinematic effects of this relatively common structural geometry. Within the fault ramp segment there are greater incremental strain magnitudes, out-of-the-plane motion, and flattening strains. Additionally, data from this model suggests that gravitational strains potentially have a significant effect on the strain distribution within a deforming thrust wedge. M. Mookerjee is formerly Matthew Strine.  相似文献   

Microwave Neutral Line Associated Source and a Current Sheet     

A. M. Uralov  V. V. Grechnev  G. V. Rudenko  I. G. Rudenko  H. Nakajima 《Solar physics》2008,249(2):315-335

Neutral Line associated Sources (NLSs) are quasi-stationary microwave sources projected onto vicinities of the neutral line of the photospheric magnetic field. NLSs are often precursors of powerful flares, but their nature is unclear. We endeavor to reveal the structure of an NLS and to analyze a physical connection between such a source with a site of energy release in the corona above NOAA 10488 (October/November 2003). Evolution of this AR includes emergence and collision of two bipolar magnetic structures, rise of the main magnetic separator, and the appearance of an NLS underneath. The NLS appears at a contact site of colliding sunspots, whose relative motion goes on, resulting in a large shear along a tangent. Then the nascent NLS becomes the main source of microwave fluctuations in the AR. The NLS emission at 17 GHz is dominated by either footpoints or the top of a loop-like structure, an NLS loop, which connects two colliding sunspots. During a considerable amount of time, the emission dominates over that footpoint of the NLS loop, where the magnetic field is stronger. At that time, the NLS resembles a usual sunspot–associated radio source, whose brightness center is displaced towards the periphery of a sunspot. Microwave emission of an X2.7 flare is mainly concentrated in an ascending flare loop, initially coinciding with the NLS loop. The top of this loop is located at the base of a non-uniform bar-like structure visible in soft X-rays and at 34 GHz at the flare onset. We reveal i) upward lengthening of this bar before the flare onset, ii) the motion of the top of an apparently ascending flare loop along the axis of this bar, and iii) a non-thermal microwave source, whose descent along the bar was associated with the launching of a coronal ejection. We connect the bar with a probable position of a nearly vertical diffusion region, a site of maximal energy release inside an extended pre-flare current sheet. The top of the NLS loop is located at the bottom of this region. A combination of the NLS loop and diffusion region constitutes the skeleton of a quasi-stationary microwave NLS.  相似文献   

海洋可再生资源权益资产负债表研究——以山东省海洋捕捞为例          下载免费PDF全文

姜旭朝  张灵育 《海洋开发与管理》2017,34(10):77-84

文章借鉴自然资源资产负债表的编制框架和海洋资源的统计核算等相关理论,通过确认海洋资源的产权和最大可持续产量,编制海洋可再生资源权益资产负债表。基于修正模型以及1988—2015年山东省海洋渔业相关数据,计算山东省海洋捕捞年度最大可持续产量,继而编制2015年山东省海洋渔业捕捞权益资产负债表。结果表明:山东省自1996年起出现捕捞资源超采问题,1997—2001年过度捕捞情况最为严重,2002年后在相关规定实施和资源量大减的双重压力下捕捞量有所降低但超采依旧严重。实例证明,编制海洋资源权益资产负债表可为海洋资源权益交易和综合管理提供依据,具有可行性和重要性。  相似文献   

The Neoproterozoic continental rift magmatism of the eastern Jiangnan orogen: new evidence from the mafic sheets in northern Zhejiang Province,South China     

Xiao-Xiong Ma  Chao Zhou  Qing Lv  Hong-Yan Gu  Wei-Wei Wu 《International Geology Review》2017,59(7):829-844

Massive mafic sheets were recently recognized intruding the Neoproterozoic strata in Fuyang area, eastern Jiangnan orogen. Geochronological, geochemical, and isotopic studies were carried out to understand their mantle source, crust–mantle interaction, and tectonic setting. LA-ICP-MS U-Pb zircon data indicate that the sheets were generated at 808 ± 7 Ma. The mafic sheets consist of two groups: high Ti and low Ti. They are enriched in light rare earth elements (LREE; 3.3–5.3 ppm) and show negligible Eu anomalies (δEu = 0.77–1.12). They also have strong large-ion lithophile element (LILE; Sr, K, Rb, Ba) enrichment, moderately strong high-field-strength element (HFSE) enrichment (except for Nb-Ta depletion), and positive εNd(t) (5.1–9.1). Geochemical and isotopic data indicate that the mafic sheets were generated from a depleted asthenospheric mantle source. The high-Ti mafic sheets have higher HFSE contents and less Nb-Ta depletion than the low Ti series, indicating a lower degree of partial melting and crustal contamination. The mafic sheets grew in a within-plate setting, concurrent with the ~820–750 Ma rifting events in the eastern Jiangnan orogen. They are likely related to the breakup of the Rodinia supercontinent.  相似文献   

川西龙门山前上三叠统小塘子组沉积环境、构造含意与含气远景   总被引：1，自引：0，他引：1  

赵霞飞  刘树根  彭靖淞  董顺利  张银德 《地质学报》2018,92(3):604-617

在实测绵竹汉旺和广元何家湾小塘子组(T_3t)地层剖面的基础上,详细研究了它们的沉积相。何家湾T_3t属浅水环境:滨面砂坝、陆架泥、潮坪和浪控三角洲。汉旺T_3t则以显著的深水相为特征:滨面砂坝,海湾泥、中缓坡水道与滑塌席、三角洲前缘沉积。对汉旺剖面所含黄铁矿结核作了初步研究。T_3t总的说符合富砂泥缓坡的沉积模式。指出汉旺剖面中部的半深水泥岩标志着龙门山活跃的逆冲构造运动,而以上的HST以至须二段下部厚砂体才是构造活动平静期的产物。认为小塘子组底部滨面砂体极具天然气勘探远景。  相似文献   

RECONSTRUCTION OF PALAEO-ICE SHEETS: THE USE OF GEOMORPHOLOGICAL DATA     

JOHAN KLEMAN  INGMAR BORGSTR M 《地球表面变化过程与地形》1996,21(10):893-909

The article discusses the nature of the glacial inversion problem, which is defined as the extraction of time-slice ice-sheet flow patterns from the patchy and partly overprinted landform record present in former ice-sheet areas. A coherent inversion model for derivation of flow patterns and interior ice-sheet configuration from geomorphological data is presented. Glacial landscapes are classified according to the three criteria of internal age gradients, presence or absence of meltwater traces aligned to flow traces, and basal condition (frozen bed/thawed bed) inferred from morphology. The inversion model uses landscapes classified accordingly, spatially delineated into fans, as input data. Relative chronologies at fan intersections are used to sort fans in a relative-age stack that can be linked to stratigraphic (dating) information.  相似文献   

Reconciling Storegga tsunami sedimentation patterns with modelled wave heights: A discussion from the Shetland Isles field laboratory     

Alastair G. Dawson  Sue Dawson  Stein Bondevik  Pedro J. M. Costa  Jon Hill  Iain Stewart 《Sedimentology》2020,67(3):1344-1353

  相似文献