http://www.sciencedirect.com/science/article/pii/S1674987110000356   总被引：1，自引：1，他引：0  

P. Mahesh  Bhaskar Kundu  J.K. Catherine  V.K. Gahalaut 《地学前缘(英文版)》2011,2(1):17-22

We have analyzed the July 15,2009,Fiordland earthquake(M_w 7.8),which occurred in the southwestern part of the South Island of New Zealand.This thrust-related earthquake in the southern Fiordland subduction zone is the largest New Zealand earthquake in the past 80 years.We have constrained a rupture model for this earthquake using coseismic offsets derived from the continuous geodetic network(Global Positioning System) of the New Zealand Institute of Geological and Nuclear Sciences (GNS Science).Our anal...  相似文献   

太平洋洋底高原和海山成因——重点以Shatsky海隆成因为例     

庞洁红  李三忠  戴黎明  吴婷婷  索艳慧  IODP航次科学团队 《海洋地质与第四纪地质》2011,(2):1-10

太平洋洋底虽然有大规模的洋底高原和大量大大小小的海山,但西北太平洋的Shatsky海隆不管在构造位置上,还是在理解洋底高原成因所特有的重要证据上,都是独一无二的,对研究太平洋各隆起形成的机制有重要参考价值.目前,对Shatsky海隆的形成有3种主要假说:(1)地幔柱头假说;(2)洋中脊假说;(3)陨星撞击假说.这些假说...  相似文献   

Variability of subduction rates of the subtropical North Pacific mode waters   总被引：1，自引：0，他引：1  

胡海波  刘秦玉  张媛  刘伟 《中国海洋湖沼学报》2011,29(5):1131-1141

The climatology subduction rate for the entire Pacific is known, but the mechanism of interannual to decadal variation remains unclear. In this study, we calculated the annual subduction rates of three types of North Pacific subtropical mode waters using a general circulation model (LICOM1.0) for the period of 1958-2001. The model experiments focused on interannual variations of ocean dynamical processes under daily wind forcings and seasonal heat fluxes. The mode water formation region was defined by a potential vorticity minimum at outcrop locations. The model results show that two subduction rate maxima (>100 m/a) were located in the Subtropical Mode Water (STMW) and the Central Mode Water (CMW) formation regions. These regions are consistent with a climatologically calculated value. The subduction rate in the Eastern Subtropical Mode Water (ESTMW) formation region was smaller at about 75 m/a. The subduction rate shows clear interannual and decadal variations associated with oceanic dynamic variabilities. The average subduction rate of the STMW was much smaller during the period of 1981-1990 compared with other periods, while that of the CMW had a negative anomaly before 1975 and a positive anomaly after 1978. The variability agreed with Ekman and geostrophic advections and mixed layer depths. The interannual variability of the subduction rate for the ESTMW was smallest during 1970-1990, as a result of a weak wind stress curl. This paper explores how interannual signals from the atmosphere are stored in different parts of the ocean, and thus may contribute to a better understanding of feedback mechanisms for the Pacific Decadal Oscillation (PDO) event.  相似文献   

Wavefield decomposition for passive ocean bottom seismological data   总被引：1，自引：0，他引：1  

M. Thorwart  T. Dahm 《Geophysical Journal International》2005,163(2):611-621

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P–T evolution of the Teslin suture zone and Cassiar tectonites, Yukon, Canada: evidence for A- and B-type subduction     

V. L. HANSEN 《Journal of Metamorphic Geology》1992,10(2):239-263

Mineral composition and quantitative thermobarometric studies indicate that the Teslin-Taylor Mountain and Nisutlin terranes within the Teslin suture zone (TSZ), Yukon, record widespread high-P/T metamorphic conditions consistent with subduction zone dynamothermal metamorphism. The highest P–T conditions (575–750° C and 9–17 kbar) are preserved in tectonites formed during normal dip-slip ductile shear. Dextral strike-slip tectonites record lower P–T conditions (400–550° C and 5–8 kbar), and tectonites which show reverse shear have peak temperatures of c. 420° C and a minimum peak pressure of 3 kbar. Dynamothermal metamorphism took place in a west-dipping B-type subduction zone outboard of western North America in Permo-Triassic time. TSZ tectonites were underplated against the hangingwall plate of the subduction zone. Following subduction of the ocean basin which separated North America from the hangingwall plate, TSZ tectonites were overthrust eastward as a coherent structural package as a result of A-type subduction of Cassiar strata in early Jurassic time. (Par)autochthonous Cassiar tectonites, which comprised the leading edge of the western North American margin, record prograde moderate-P, high-T metamorphism (550–750° C and 7–13 kbar) synchronous with top-to-the-east ductile shear. Metamorphism occurred as a result of subduction of the North American margin into the TSZ subduction zone in early Jurassic time. Following metamorphism Cassiar tectonites cooled slowly from 500 to 300° C during the period middle Jurassic to middle Cretaceous. TSZ and Cassiar tectonites were deformed during changing P–T conditions. Data from each of these tectonite packages indicate that grain-scale strain partitioning may have allowed local recrystallization of individual minerals by the addition of mechanical energy. The composition of the new grains reflects the P–T conditions under which that particular grain was deformed.  相似文献   

The origin and P–T evolution of peridotites and serpentinites of NE New Caledonia: prograde interaction between continental margin and the mantle wedge     

J. A. Fitzherbert  G. L. Clarke  B. Marmo  R. Powell 《Journal of Metamorphic Geology》2004,22(4):327-344

The Pouébo and Diahot terranes of NE New Caledonia mostly comprise eclogite to blueschist facies metabasite and metasedimentary rocks that experienced c. 40 Ma metamorphism. This Eocene high‐P event has been linked with the SW‐directed obduction of the New Caledonian Ophiolite, an extensive ultramafic nappe that dominates outcrop in the south of the island. In the north, ultramafic lithologies are found only as sheets or discrete lenticular masses interleaved with, but separated from, the eclogites and blueschists by foliated talc–chlorite–serpentine–carbonate‐bearing rocks. The base of the largest and best‐preserved ultramafic body at Yambé is marked by a distinctive (2 m thick) layer of high‐P mylonite that preserves evidence for early blueschist facies conditions (S1) as inclusions in eclogite facies minerals. Textural evidence preserved in olivine‐bearing serpentinites and their bounding mafic mylonites suggest that the ultramafic bodies were emplaced within the structurally highest levels of the high‐P terrane as serpentinite tectonites sourced from hydrated mantle, formerly in the hangingwall of the Eocene subduction zone. Serpentinite emplacement accompanied burial of the NE New Caledonian margin at T<500 °C and P<16 kbar. The ultramafic fragments were buried to depths of 50–60 km in the subduction zone, where olivine was stable and coarse‐grained garnet–omphacite‐rich assemblages developed in low strain domains within enclosing mylonites. Host metabasic and metasedimentary rocks from the structurally highest portions of the high‐P belt have a prograde record identical to that of the ultramafic tectonites. The early emplacement and similar P–T history of host rocks and ultramafic masses suggest that NE New Caledonia preserves a fossil slab/mantle–wedge boundary reactivated during exhumation.  相似文献   

Experimental dehydration kinetics of serpentinite using pore volumometry     

S. LLANA-FÚNEZ  K. H. BRODIE  E. H. RUTTER  J. C. ARKWRIGHT 《Journal of Metamorphic Geology》2007,25(4):423-438

A series of dehydration experiments was carried out on both intact rock and cold-pressed powdered samples of serpentinite at temperatures in the range 535–610 °C, 100–170 °C above the onset of the breakdown temperature of 435 °C. Pore water pressures near 120 MPa were servo-controlled using a pore volumometer that also allowed dehydration reaction progress to be monitored through measurement of the amount of evolved water. Effective hydrostatic confining pressures were varied between 0 and 113 MPa. The reaction rate of intact specimens of initially near-zero porosity was constant up to 50–80% reaction progress at any given temperature, but decreased progressively as transformation approached completion. Water expulsion rates were not substantially affected by elevation of effective pressures that remained insufficient to cause major pore collapse. An Arrhenius relation links reaction rate to temperature with an activation enthalpy of 429 ± 201 and 521 ± 52 kJ mol⁻¹ for powdered and intact specimens, respectively. Microstructural study of intact specimens showed extensive nucleation beginning at pre-existing cracks, veins and grain boundaries, and progressing into the interior of the lizardite grains. Extrapolation of these data towards equilibrium temperature provides an upper bound on the kinetics of this reaction in nature.  相似文献   

不同类型俯冲带地震水平向地震动阻尼修正系数对比研究          下载免费PDF全文

康莉莉    刘名吉  张洪博  杨青松 《世界地震工程》2021,(2):183-191

基于日本KiK-Net、K-Net地震台网和太平洋地震工程中心（PEER）的14 713条地震动记录,比较了俯冲带地区浅壳上地幔地震、板内地震和板间地震的水平向地震动加速度反应谱阻尼修正系数（DMF）和位移反应谱阻尼修正系数（DMF）的差异,并进行了5%置信水平下的假设检验,探究了俯冲带地区不同地震类型对DMF的影响。结果显示:在大多数谱周期,不同地震类型的DMF存在统计意义上的显著差异;在低阻尼比中短周期时,加速度谱DMF和位移谱DMF基本相同;在高阻尼比长周期时,不同地震类型的加速度谱DMF差异大于位移谱DMF差异。研究表明:俯冲带地震水平向地震动DMF需要考虑不同地震类型的影响。  相似文献   

中国地壳运动观测网络基准站重力场变化的海潮负荷信号改正问题   总被引：7，自引：0，他引：7  

孙和平  周江存 《地球科学进展》2002,17(1):39-43

利用最新的全球海潮模型（Csr3．0，Fes95．2，Tpxo2和Csr4．0）和原有的Schwiderski海潮模型以及中国近海海潮数据和标准地球模型负荷格林函数，采用直接褶积积分方法研究了中国地壳运动观测网络25个基准站重力固体潮观测中的海潮负荷效应问题，计算了 8个主要潮汐波的负荷振幅和相位，构制了北京和上海等10个台站重力负荷随时间变化函数。  相似文献   

Delamination and ultra‐deep subduction of continental crust: constraints from elastic wave velocity and density measurement in ultrahigh‐pressure metamorphic rocks     

Z. ZHAO  Y. NIU  N. I. CHRISTENSEN  W. ZHOU  Q. HOU  Z. M. ZHANG  H. XIE  Z. C. ZHANG  J. LIU 《Journal of Metamorphic Geology》2011,29(7):781-801

Thirty‐three samples, including 22 eclogites, collected from the Dabie ultrahigh‐pressure (UHP) metamorphic belt in eastern China, have been studied for seismic properties. Compressional (V_p) and shear wave (V_s) velocities in three mutually perpendicular directions under hydrostatic pressures up to 1.0 GPa were measured for each sample. At 1.0 GPa, V_p (7.5–8.4 km s^?1), V_s (4.2–4.8 km s^?1), and densities (3.2–3.6 g cm^?3) in the UHP eclogites are higher than those of UHP orthopyroxenite (7.3–7.5 km s^?1, 4.1–4.3 km s^?1, 3.2–3.3 g cm^?3, respectively) and HP eclogites (7.1–7.9 km s^?1, 4.0–4.5 km s^?1, 3.1–3.5 g cm^?3, respectively). Kyanitites (with 99.5% kyanite) show extremely high velocities and density (9.37 km s^?1, 5.437 km s^?1, 3.581 g cm^?3, respectively). The eclogites show variation of V_p‐ and V_s‐anisotropy up to 9.70% and 9.17%, respectively. Poisson’s ratio (σ) ranges from 0.218 to 0.278 (with a mean of 0.255) for eclogites, 0.281–0.298 for granulites and 0.248 to 0.255 for amphibolites. The σ values for serpentinite (0.341) and marble (0.321) are higher than for other lithologies. The elastic moduli K, G, E of kyanitite were obtained as 163, 102 and 253 GPa, respectively. The V_p and density of representative UHP metamorphic rocks (eclogite & kyanitite) were extrapolated to mantle depth (15 GPa) following a reasonable geotherm, and compared to the one dimension mantle velocity and density model. The comparison shows that V_p and density in eclogite and kyanitite are greater than those of the ambient mantle, with differences of up to ΔV_p > 0.3 km s^?1 and Δρ > 0.3–0.4 g cm^?3, respectively. This result favours the density‐induced delamination model and also provides evidence in support of distinguishing subducted high velocity materials in the upper mantle by means of seismic tomography. Such ultra‐deep subduction and delamination processes have been recognized by seismic tomography and geochemical tracing in the postcollisional magmatism in the Dabie region.  相似文献