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1.
太平洋卫星测高重力场与地球动力学特征 总被引：6，自引：1，他引：6
通过多卫星测高数据的综合处理，获得西太平洋卫星测高重力场，进行不同尺度、深度构造动力信息的分离，探讨诸边缘海盆的地球动力学问题。测高大地水准面反映了研究区板块相互作用的特点，其高频成分可以刻画各海盆的构造特征。测高空间重力异常也可刻画陆架构造及盆地分布，由其推算出的海底地形含有大量的海底构造信息。各边缘海盆的莫霍面埋深具有往南变浅的趋势，与菲律宾海各海盆的莫霍面埋深大致相当，说明岛弧两侧的构造动力强度基本相似。大尺度地幔流应力场总体上反映了欧亚板块向东南蠕散和太平洋板块向北西扩张的特点；日本海北侧和南海巽他陆架的中尺度上地幔对流与地幔柱之间有着密切关系，西菲律宾海的上地幔对流强化了日本-琉球-台湾-菲律宾岛弧的活动强度；小尺度地幔流主要限于软流圈层内部，在各海盆分散，而在冲绳海槽和马里亚纳海槽则会聚，可与均衡重力异常类比。还讨论了大、中、小地幔流体系的特点及相互之间的关系，籍以阐明海盆及海槽演化的地球动力学过程。 相似文献
2.
以南桑威奇俯冲带为例,根据EGM2008超高阶地球重力场模型、卫星重力数据为基础,利用移去-恢复原理计算了研究区大地水准面,实现了研究区不同场源深度大地水准面异常信息的分离,根据Runcorn模型计算了研究区小尺度地幔对流应力场,并结合天然地震空间展布和前人研究成果,对俯冲带结构特征与地幔对流模式进行了探讨。结果表明:南桑威奇俯冲带具有俯冲倾角较大、地震震级较低、弧前侵蚀明显等典型的马里亚纳型俯冲带特征,俯冲带南北部俯冲深度存在明显差异,中段偏北俯冲深度可达500 km;受到软流圈与上地幔上部物质密度差异的控制,东斯科舍海脊下存在沿海脊轴向南流动强地幔流;俯冲带结构与小尺度地幔对流应力场具有很强的相关性。本研究对于搞清南桑威奇俯冲带深部构造特征,理解俯冲运动、地幔对流方向及其动力控制机制提供了新的研究思路和方法。 相似文献
3.
Daniel S. Scheirer Ken C. Macdonald Donald W. Forsyth Yang Shen 《Marine Geophysical Researches》1996,18(1):13-52
A widespread seamount province, the Rano Rahi Field, is located near the superfast spreading Southern East Pacific Rise (SEPR) between 15°–19° S. Particularly abundant volcanic edifices are found on Pacific Plate aged 0 to 6.5 Ma between 17°–19° S, an area greater than 100,000 km2. The numbers of seamounts and their volume are several times greater than those of a comparablysurveyed area near the Northern East Pacific Rise (NEPR), 8°–17° N. Most of the Rano Rahi seamounts belong to chains, which vary in length from 25 km to >240 km and which are very nearly collinear with the Pacific absolute and relative plate motion directions. Bends of 10°–15° occur along a few of the chains, and some adjacent chains converge or diverge slightly. Many seamount chains have fluctuations in volume along their length, and statistical tests suggest that some adjacent chains trade-off in volume. Several seamount chains split into two lines of volcanoes approaching the axis. In general, seamount chains composed of individual circular volcanoes are found near the axis; the chains consist of variably-overlapping edifices in the central part of the survey; to the west, volcanic ridges predominate. Near the SEPR, the volume of nearaxis seamount edifices is generally reduced near areas of deflated cross-sectional area of the axial ridge. Fresh lava flows, as imaged by sidescan sonar and sampled by dredging, exist around some seamounts throughout the entire survey area, in sharp contrast to the absence of fresh flows beyond 30 km from the NEPR. Also, the increases in seamount abundance and volume extend to much greater crustal ages than near the NEPR. Seamount magnetization analysis is also consistent with this wider zone of seamount growth, and it demonstrates the asynchronous formation of most of the seamount chains and volcanic ridges. The variety of observations of the SEPR seamounts suggests that a number of factors and mechanisms might bring about their formation, including the mantle upwelling associated with superfast spreading, off-axis mantle heterogeneities, miniplumes and local upwelling, and the vulnerability of the lithosphere to penetration by volumes of magma. In particular, we note the association of extensive, recent volcanism with intermediate wavelength gravity lineaments lows on crust aged 6 Ma. This suggests that the lineaments and some of the seamounts share a common cause which may be related to ridge-perpendicular asthenospheric convection and/or some manner of extension in the lithosphere. 相似文献
4.
Dziak Robert P. Fox Christopher G. Embley Robert W. Nabelek John L. Braunmiller Jochen Koski Randolph A. 《Marine Geophysical Researches》2000,21(5):423-450
Bathymetric, hydro-acoustic, seismic, submersible, and gravity data are used to investigate the active tectonics of the eastern Blanco Transform Fault Zone (BTFZ). The eastern BTFZ is dominated by the 150 km long transform-parallel Blanco Ridge (BR) which is a right-lateral strike-slip fault bordered to the east and west by the Gorda and Cascadia Depressions. Acoustic locations, fault-parameter information, and slip vector estimates of 43 earthquakes (M
w3.8) that occurred along the eastern BTFZ over the last 5 years reveal that the Blanco Ridge is a high-angle right-lateral strike-slip fault, with a small component of dip-slip motion, where the Juan de Fuca plate is the hanging wall relative to the Pacific plate. Furthermore, the Cascadia and Gorda basins are undergoing normal faulting with extension predominantly oblique to the transform trend. Seafloor submersible observations agree with previous hypotheses that the active transform fault trace is the elongate basin that runs the length of the BR summit. Brecciated and undeformed basalt, diabase, and gabbro samples were collected at the four submersible survey sites along the Blanco Ridge. These petrologic samples indicate the Blanco Ridge is composed of an ocean crustal sequence that has been uplifted and highly fractured. The petrologic samples also appear to show an increase in elevation of the crustal section from east to west along the Blanco Ridge, with gabbros exposed at a shallower depth farther west along the southern (Pacific plate side) BR ridge flank. Further supporting evidence for BR uplift exists in the seismic reflection profiles across the BR showing uplift of turbidite sequences along the north and south ridge base, and gravity and magnetics profiles that indicate possible basement uplift and a low-density zone centered on the ridge's Pacific plate side. The BR formation mechanism preferred here is first, uplift achieved partially through strike-slip motion (with a small dip-slip component). Second, seawater penetration along the fault into the lower crust upper mantle, which then enhanced formation and intrusion of a mantle-derived serpentinized-peridotite diapir into the shallow ocean crust, causing further uplift along the fault. 相似文献
5.
东海陆架区中北部前第三系基底综合地球物理研究 总被引：6，自引：0，他引：6
从地震、钻井资料出发,结合周边地质特征,推断东海陆架区中北部存在中生界和古生界地层。结合地震资料,正演消除了海底和新生界密度不均匀在重力场上的影响,定量反演重、磁力异常并求取了重力基底和磁性基底。重力基底的特征在东西分带的大背景下表现出“靠陆侧南北分块,靠洋侧东西分带”的特点。西湖凹陷区的磁性基底与重力基底埋深大致相同,不一致地方可能是受岩体的影响。西湖凹陷以西地区,包括海礁凸起等单元,总体出现磁性基底埋深比重力基底埋深深2km左右,初步解释为古生界地层的反映。中生界地层厚度的分布也具有东西分带和南北分块特点。西湖凹陷西缘的中生界地层厚度大,其中带中生界虽然含有一定的火山岩或火山碎屑岩,但沉积岩更多,这对下一步的油气勘探有利。 相似文献
6.
Takeshi Matsumoto 《Marine Geophysical Researches》1996,18(2-4):147-161
The thickness anomaly of lithosphere in the North Fiji Basin, Lau Basin and the surrounding area was obtained from gravity data derived by satellite altimetry, using crustal thickness determined by available seismic refraction studies. It was revealed that the North Fiji Basin is an isolated asthenospheric dome and that the lithospheric thickness is about 50km less than that of the surrounding area. Such a lithospheric structure and surface topographic feature suggest a plume-like mantle upwelling beneath these basins. The result of numerical simulation shows the possibility of opening of the back-are area and change of subduction polarity which occurred at the first stage of the evolution of the North Fiji Basin. As the lifetime of the southwestern Pacific marginal basins is limited to some 10 million years in most cases, the heat source (plume) which initiates these marginal basins might be sporadic, and their expansion will end when the heat source is wholly consumed. 相似文献
7.
南海西北部与红河地区地球物理场及其地壳深部结构特征 总被引：10，自引：0，他引：10
分析了南海西北部与红河地区地球物理场特征，计算了研究区重、磁资料的一阶小波细节变换、四阶小波逼近变换。根据重力场资料以及南海北部盆地钻井取样的测试结果，同时参考在研究区进行的地震勘探结果，对研究区的地壳结构进行了反演计算。结果表明，研究区域地壳结构较为复杂，地壳厚度在17—38km之间，总的趋势由陆向洋地壳厚度逐渐减薄，反映出该区域地壳具有陆壳、过渡壳的性质，同时存在上地幔隆起区及凹陷区。用地震层折成像结果与重力资料计算出的地壳分布趋势进行了对比验证。根据地幔对流结果探讨了研究区深部地球动力学特征及其与深部地壳结构的关系。 相似文献
8.
Spectral analysis techniques have been applied to data sets of gravity and topography selected across fracture zones with large offset in the Equatorial and Central Atlantic Ocean and processed independently for each fracture zone. Three simple compensation models, two in local isostatic equilibrium (Airy I and II) and one in regional equilibrium (Plate model) have been tested. It is found that the free-air anomalies are primarily controlled by the topography and its isostatic response. For short wavelengths, admittance can be explained either by the effect of uncompensated sea floor topography with high density basement or by the effect of uncompensated sea floor topography with normal oceanic basement density but accompanied by a crust of constant thickness. For intermediate wavelengths, admittance for the Romanche fracture zone agrees best with a local isostatic model in which compensation is achieved by a less dense material in the upper mantle. No such evidence exists for the Vema and Chain fracture zones for which topography could just as well be regionally supported by an elastic plate 3 to 10 km thick. For longer wavelengths, the admittances computed for the three fracture zones are compatible with a thermal compensation of the topography. 相似文献
9.
Gravity and multichannel seismic reflection constraints on the lithospheric structure of the Canary Swell 总被引：1，自引：0，他引：1
Deep penetrating multichannel seismic reflection and gravity data have been used to study the lithospheric structure of the Canary Swell. The seismic reflection data show the transition from undisturbed Jurassic oceanic crust, away from the Canary Islands, to an area of ocean crust strongly modified by the Canary volcanism (ACV). Outside the ACV the seismic records image a well layered sedimentary cover, underlined by a bright reflection from the top of the igneous basement and also relatively continuous reflections from the base of the crust. In the ACV the definition of the boundary between sedimentary cover and igneous basement and the crust-mantle boundary remains very loose. Two-dimensional gravity modelling in the area outside the influence of the Canary volcanism, where the reflection data constrain the structure of the ocean crust, suggests a thinning of the lithosphere. The base of the lithosphere rises from 100 km, about 400 km west of the ACV, to 80 km at the outer limit of the ACV. In addition, depth conversion of the seismic reflection data and unloading of the sediments indicate the presence of a regional depth anomaly of an extension similar to the lithospheric thinning inferred from gravity modelling. The depth anomaly associated with the swell, after correction for sediment weight, is about 500 m. We interpret the lithospheric thinning as an indication of reheating of old Mesozoic lithosphere beneath the Canary Basin and along with the depth anomaly as indicating a thermal rejuvenation of the lithosphere. We suggest that the most likely origin for the Canary Islands is a hot spot. 相似文献
10.
Structure of the basins of the White Sea rift systems 总被引：1，自引：0，他引：1
For the first time, the structure of the sedimentary basins of the Late Proterozoic rift system in the White Sea is characterized based on a set of new marine geological geophysical data such as the results of the common depth point seismic method, gravity and magnetic data, and seismoacoustics. The main tectonic structures in the topography of the heterogeneous basement within the basin of the White Sea are distinguished and described. A structural tectonic scheme of the basement surface is presented. The thicknesses of the sediments are estimated and the stratigraphic confinement of the seismic units recognized is done. 相似文献
11.
12.
台湾海峡及其邻区岩石圈层下地幔流应力场 总被引：3，自引：0，他引：3
本文应用卫星测到的2～30阶球谐函数系数(GEM8) 计算了台湾海峡及邻近地区的岩石圈层下地幔流应力场。在比较了该区域的构造地质以后,发现应力场的方向,尤其是在板块收敛区域的甚高阶场(26～30阶)的方向与在菲律宾海和南海等区域的板块运动方向一致。 相似文献
13.
Marie-Helene Cormier Daniel S. Scheirer Ken C. Macdonald 《Marine Geophysical Researches》1996,18(1):53-84
Nearly complete side-scan, bathymetry and magnetic coverage documents the evolution of the geometry of the East Pacific Rise (EPR) between 16° and 19° S since 5 Ma. Lineaments visible in SeaMARC II, H-MR1 and Sea Beam 2000 side-scan data correspond dominantly to normal fault scarps which have developed in the axial region perpendicular to the least compressive stress. Except near overlapping spreading centers (OSCs), the lineament orientations are taken to represent the perpendicular to the instantaneous Pacific-Nazca spreading direction. Their dominant orientation in the axial region is 012°, in good agreement with the prediction of the current model of relative plate motion (DeMets et al., 1994). However, the variations of the lineament azimuths with age show that there has been a small (3°–5°) clockwise change in the Nazca-Pacific relative motion since 5 Ma. There is also a distinct population of lineaments which strike counterclockwise to the ambient orientation. These discordant lineaments form somewhat coherent patterns on the seafloor and represent the past migration tracks of several left-stepping OSCs. Concurrent analysis of these discordant zones and the magnetic anomalies, reveals that up to 1 Ma, the EPR was offset by a few large, left-stepping OSCs. These OSCs were bisected into smaller OSCs by new spreading segments forming within their overlap basins. The smaller OSCs proceeded to migrate rapidly and were further bisected by newly spawned ridge segments until the present staircase of small, left-stepping OSCs was achieved. By transferring lithosphere from one plate to the other, these migration events account remarkably well for the variable spreading asymmetry in the area. Between 16° and 19° S, the present EPR is magmatically very robust, as evidenced by its inflated morphology, the profuse volcanic and hydrothermal activity observed from submerisbles and towed cameras, the geochemistry of axial basalts, and seismic and gravity data. Since 1 Ma, all the OSCs have migrated away from the shallowest, most robust section of the ridge between 17° and 17°30 S, which was previously offset by a large OSC. We propose that the switch from a presumed starved magmatic regime typically associated with large OSCs to the presently robust magmatic regime occurred when the EPR overrode a melt anomaly during its westward migration relative to the asthenosphere. The resulting increase in melt supply at 17°–17°30 S has fed the migration of axial discontinuities for this section of the southern EPR since 1 Ma. 相似文献
14.
试论东海陆架盆地的基底构造演化和盆地形成机制 总被引：4，自引：0，他引：4
本文主要根据东海陆架盆地和周边的地质、地球物理资料,分析盆地的基底岩性特征、结构特征。认为东海陆架盆地的基底除元古界片麻岩外,还分布有一定范围的中生界及古生界。基底构造特征是纵向上多层次,横向上不均一,南北有别,东西分带。构造演化上经历了张、合、压、扭等复杂过程。 相似文献
15.
利用径向基函数多尺度分析方法,将GOCO05S模型海洋大地水准面分解为3个尺度,并进行详细的分析统计。分解后重构的大地水准面精度达到了±0.02m,表明了径向基函数出色的多尺度分析能力。对不同深度层面上大地水准面异常的分布及成因做了深入探讨。浅层上地幔大地水准面异常主要分布于板块边缘,呈条状,与火山热点源分布类似;深层上地幔大地水准面异常和大洋中脊所在位置部分吻合,主要呈带状或块状,与上地幔的对流有关;中间层上地幔的大地水准面异常形态介于上述两者之间,主要受火山热点源和地幔对流的综合影响。 相似文献
16.
侏罗纪洋壳为现存最古老的海洋地壳, 残留在地球表面上很少, 目前对于侏罗纪洋壳的断裂特征和构造变形了解很少。本文利用高分辨率的反射地震剖面精细解释了位于西太平洋的侏罗纪洋壳基底、沉积地层和断裂结构, 发现在研究区存在基底断层、沉积断层和垮塌断层三种类型的断裂构造, 并对其走向、倾角、断距等几何参数与变形特征进行了推测和定量研究。研究还发现, 基底断层是洋壳受到板块伸展拉张而产生的, 在后期海底沉积过程中持续发育并错断上覆沉积物, 在海底形成明显的断层陡坎。沉积断层是沉积地层自身重力作用的产物,受到沉积地层岩石性质的控制。垮塌断层是岩浆侵出或者侵入形成海山, 导致洋壳及其上覆沉积局部抬升并向两侧推移, 引起先存的基底断层和沉积断层重新错动产生的。研究区内切断洋壳基底和上覆沉积的活动断层的推测走向大体符合侏罗纪洋壳基底面起伏、重力异常骤变界面以及地磁异常条带等的走向, 表明这些断裂从侏罗纪洋中脊的海底扩张中演变而来, 并且持续活动至今。这些发育在古老洋壳上的断层能够长时间让水进入岩石圈并进入俯冲带及地球内部, 从而促进地球水循环。尽管目前尚未发现这些断裂产生大地震, 但这些断层可能随着板块俯冲而演变成俯冲带地震大断裂, 今后研究应该关注这类断层在靠近海沟之前的演化规律和潜在地震风险。 相似文献
17.
18.
Geology of the Continental Margin of Enderby and Mac. Robertson Lands, East Antarctica: Insights from a Regional Data Set 总被引：1，自引：0，他引：1
H. M. J. Stagg J. B. Colwel N. G. Direen P. E. O’Brien G. Bernardel I. Borissova B. J. Brown T. Ishirara 《Marine Geophysical Researches》2004,25(3-4):183-219
In 2001 and 2002, Australia acquired an integrated geophysical data set over the deep-water continental margin of East Antarctica
from west of Enderby Land to offshore from Prydz Bay. The data include approximately 7700 km of high-quality, deep-seismic
data with coincident gravity, magnetic and bathymetry data, and 37 non-reversed refraction stations using expendable sonobuoys.
Integration of these data with similar quality data recorded by Japan in 1999 allows a new regional interpretation of this
sector of the Antarctic margin.
This part of the Antarctic continental margin formed during the breakup of the eastern margin of India and East Antarctica,
which culminated with the onset of seafloor spreading in the Valanginian. The geology of the Antarctic margin and the adjacent
oceanic crust can be divided into distinct east and west sectors by an interpreted crustal boundary at approximately 58° E.
Across this boundary, the continent–ocean boundary (COB), defined as the inboard edge of unequivocal oceanic crust, steps
outboard from west to east by about 100 km.
Structure in the sector west of 58° E is largely controlled by the mixed rift-transform setting. The edge of the onshore Archaean–Proterozoic
Napier Complex is downfaulted oceanwards near the shelf edge by at least 6 km and these rocks are interpreted to underlie
a rift basin beneath the continental slope. The thickness of rift and pre-rift rocks cannot be accurately determined with
the available data, but they appear to be relatively thin. The margin is overlain by a blanket of post-rift sedimentary rocks
that are up to 6 km thick beneath the lower continental slope.
The COB in this sector is interpreted from the seismic reflection data and potential field modelling to coincide with the
base of a basement depression at 8.0–8.5 s two-way time, approximately 170 km oceanwards of the shelf-edge bounding fault
system. Oceanic crust in this sector is highly variable in character, from rugged with a relief of more than 1 km over distances
of 10–20 km, to rugose with low-amplitude relief set on a long-wavelength undulating basement. The crustal velocity profile
appears unusual, with velocities of 7.6–7.95 km s−1 being recorded at several stations at a depth that gives a thickness of crust of only 4 km. If these velocities are from
mantle, then the thin crust may be due to the presence of fracture zones. Alternatively, the velocities may be coming from
a lower crust that has been heavily altered by the intrusion of mantle rocks.
The sector east of 58° E has formed in a normal rifted margin setting, with complexities in the east from the underlying structure
of the N–S trending Palaeozoic Lambert Graben. The Napier Complex is downfaulted to depths of 8–10 km beneath the upper continental
slope, and the margin rift basin is more than 300 km wide. As in the western sector, the rift-stage rocks are probably relatively
thin. This part of the margin is blanketed by post-rift sediments that are up to about 8 km thick.
The interpreted COB in the eastern sector is the most prominent boundary in deep water, and typically coincides with a prominent
oceanwards step-up in the basement level of up to 1 km. As in the west, the interpretation of this boundary is supported by
potential field modelling. The oceanic crust adjacent to the COB in this sector has a highly distinctive character, commonly
with (1) a smooth upper surface underlain by short, seaward-dipping flows; (2) a transparent upper crustal layer; (3) a lower
crust dominated by dipping high-amplitude reflections that probably reflect intruded or altered shears; (4) a strong reflection
Moho, confirmed by seismic refraction modelling; and (5) prominent landward-dipping upper mantle reflections on several adjacent
lines. A similar style of oceanic crust is also found in contemporaneous ocean basins that developed between Greater India
and Australia–Antarctica west of Bruce Rise on the Antarctic margin, and along the Cuvier margin of northwest Australia. 相似文献
19.
H. L. Davies E. Honza D. L. Tiffin J. Lock Y. Okuda J. B. Keene F. Murakami K. Kisimoto 《Geo-Marine Letters》1987,7(3):153-160
The western Solomon Sea is bounded by the Paleogene collision complex of the Papuan Peninsula to the south, and land masses constructed by Cainozoic volcanism to the north and cast. Oblique collision of two trenches in the western Solomon Sea, and concomitant collision of upper plates, have produced structural complexities that may include the local doubling of crustal thickness, coincident with a strong negative gravity anomaly west of 149°E. Lateral flexing of the subducted plate in the New Britain Trench may have caused flexure of the upper plate; this flexure is expressed in the gravity field, faults, dip-slopes, exposure of basement, and alignment of volcanoes. 相似文献
20.
We present previously unreported depth anomalies in the Arabian Basin, northwest Indian Ocean, to provide constraints on the
evolution of the oceanic lithosphere of that basin. The depth anomaly reported in this study was calculated as the difference
between the observed depth to oceanic basement (corrected for sediment load) and the calculated depth to oceanic basement
of the same age. The results indicate an anomalous depth to basement of oceanic crust in the Arabian Basin in the age bracket
of 63–42 Ma, suggesting that subsidence in this basin does not follow the age–depth relationship of normal oceanic crust.
The depth anomalies in the basin vary from +501 to −905 m. A negative depth anomaly zone, mapped in the eastern part of the
basin near the Laccadive Ridge, indicates that here the basement depth is shallower than predicted. By contrast, a positive
depth anomaly zone, mapped in the western part of the basin, indicates a deeper basement depth than expected. We propose that
the excess subsidence of basement of the western part of the basin is probably caused by a relatively cold mantle, compared
to the nearby eastern part of the basin which is affected by the intense thermal field of the former Reunion hotspot. Here,
the rise in oceanic basement is caused by the vertical upwelling of oceanic crust due to convection, followed by a lateral
across-axis flow facilitated by the Reunion hotspot at the time of spreading in early Tertiary times. This interpretation
is in good agreement with spreading-ridge propagation and ridge-hotspot interaction reported earlier for the basin. 相似文献