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1.
东海莫霍面起伏与地壳减薄特征初步分析 总被引：3，自引：0，他引：3
收集、整理大量由地震剖面提供的沉积层厚度资料,得到东海沉积层等厚图。对完全布格重力异常进行沉积层重力效应改正后,得到剩余重力异常,利用地震资料揭示的莫霍面深度值来约束界面反演得到东海莫霍面埋深。结果表明,东海陆架盆地莫霍面深度在25～28 km之间平缓变化,地壳厚度为14～26 km,西厚东薄;冲绳海槽盆地莫霍面深度为16～26 km,地壳厚度为12～22 km,北厚南薄。东海陆架盆地东部与冲绳海槽盆地南部地壳减薄明显,拉张因子分别达到2.6和3。初步分析认为冲绳海槽地壳以过渡壳为主,并未形成洋壳。 相似文献
2.
南极布兰斯菲尔德海峡及周边区域是南极大陆火山、地震等新构造活动最活跃的地区,与南设得兰海沟、南设得兰群岛一同构成南极大陆边缘现存唯一的"沟-弧-盆"构造体系。本文基于"雪龙"船第28、第30航次实测数据及两个航次的国际共享资料,利用均衡改正数据处理方法获得布兰斯菲尔德海峡的莫霍面深度及其分布规律,分析深部构造-断裂的区域分布及其重力异常特征等。布兰斯菲尔德海峡内的空间重力异常呈条带状分布,走向总体与地形相近,布格重力异常则由两侧向中间升高,大致在坡折处形成异常场值为100×10-5 m/s2的分界线,在中央次海盆和东部次海盆海山处形成两个异常高值圈闭,异常值最高为150×10-5 m/s2。莫霍面深度以弧后扩张中心为最低值,向南设得兰群岛和南极半岛两个方向递增,深度从12 km递增至陆坡位置的24 km。 相似文献
3.
基于中国南极考察第28航次和第30航次所获得的实测重力数据,结合NGDC的部分资料,我们采用最小二乘算法平差处理布兰斯菲尔德海峡内470 610个有效船测重力观测值点,使航次内、航次间观测误差达到极小。针对不同航次、不同船只数据交点的分布情况,对平差方式进行不同程度的微调,完成对研究区4组数据的平差。其中,中国南极考察第28航次船测数据交点误差的标准差由平差前的5.5×10-5 m/s2降为平差后的1.78×10-5m/s2,而全部125个交点平差后标准差降为1.545×10-5 m/s2。在此基础上,绘制了研究区空间重力异常图,相比卫星重力异常数据,融合成果数据能更真实地反映海底火山等特征,从而进一步提高了数据精度。 相似文献
4.
《海洋地质与第四纪地质》2014,(5)
台湾地区空间重力异常幅值在-240~340mGal之间变化,布格重力异常幅值在-140~380mGal之间变化,重力异常及圈闭走向呈现北东、北北东向。将小波分析方法引入台湾地区的重力异常数据处理,经过分析比对,台湾地区布格重力异常小波分析三阶逼近结果代表莫霍面起伏形态,利用重力数据反演了深部界面莫霍面,研究区莫霍面深度为12~32km,莫霍面展布呈现北东走向,台湾岛区莫霍面深,在24~31km之间变化,由西北往东南为厚-薄-厚分布,台湾东部海区莫霍面深度浅,在12~17km之间变化,台湾岛属于陆壳结构,靠近菲律宾海的台湾岛外海地区,属于海洋性地壳结构。 相似文献
5.
南海北部陆缘地壳结构探测结果分析 总被引：29，自引：4，他引：29
深部地震和重力资料反演揭示了南海北部陆缘地壳结构在总体上由北部的华南沿海（厚约30km）向南部的洋盆（5──8km）逐渐减薄。南海的近SN向拉张不仅造成南北方向地壳结构的巨大变化，也造成东西向的明显变化。在南海北部陆缘的西部，局部拉张产生了一系列裂谷构造。西沙海槽作为一条狭窄的陆内裂谷向西延伸，海槽南北两侧地壳厚度超过25km，海槽中部地壳减薄至不足10km。西端的莺歌海盆地地壳厚仅5km，缺少明显的壳内反射－折射。在珠江口盆地中部，地壳厚度在下陆坡明显减薄，地壳下部存在较薄的（3──4km）高速层（地震波速7．2──7．5km·s－1）；在珠江口盆地东部，地壳底部存在约 10km厚、300km宽的高速层。在台湾地区，由于弧陆碰撞，曾经减薄的陆壳在碰撞带增厚，莫霍面深度超过30km。南海北部陆缘在裂谷拉张和海底扩张期间岩浆活动平静，表明南海北部陆缘为非火山型陆缘。 相似文献
6.
利用中国-尼日利亚国际合作航次获得的船载重力数据,分析了尼日利亚南部大陆边缘的自由空间重力异常和布格重力异常特征,并通过两条从陆架—陆坡—陆隆一直延伸到深海盆地的重力剖面拟合出地壳密度结构。研究结果表明,地壳厚度总体上从陆架、陆坡至深海平原呈现阶梯状减薄的趋势,东侧的减薄幅度大于西侧,东侧从24 km减小到10 km,西侧从21 km减小到14 km。 相似文献
7.
长昌凹陷位于琼东南盆地深水区,向东通过西沙海槽与南海西北次海盆相通,其近东西向的展布形态明显异于深水区其他凹陷的NE-NEE向形态,为了弄清其地壳结构,从而更好地分析凹陷的结构和演化机制,这里根据深反射地震资料、VSP资料和最新重力资料对长昌凹陷的地壳结构进行了综合地球物理模拟.结果显示:长昌凹陷北侧地壳厚度为22～24 km,南侧地壳厚度约20～22 km,从两侧向长昌凹陷中央地壳厚度逐渐减薄,最薄处只有2.8 km;莫霍面深度与沉积基底呈镜像关系,沉积基底最深的地方莫霍面深度最浅,最浅深度距海平面13.8 km;凹陷中央东部存在一层厚约4 km的下地壳高速层,该层在地震剖面和层速度剖面上均可识别. 相似文献
8.
南极布兰斯菲尔德海峡及邻区地壳结构反演及构造解析 总被引：1，自引：0，他引：1
南极布兰斯菲尔德海峡及邻区是南极半岛海域火山、地震等新构造运动最活跃的地区,由于前人对资料处理解释的差异,导致盆地的构造格局仍部分存疑。本文以研究区的卫星重力数据为基础,以多道反射地震和部分岩性资料为约束,采用重震联合反演方法构建了三条横跨研究区的地壳结构剖面,并进一步研究布兰斯菲尔德海峡盆地的地壳结构。研究结果表明布兰斯菲尔德海峡盆地莫霍面深度为33—38km。菲尼克斯板块俯冲消减下沉至南设得兰岛弧之下,导致南设得兰海沟的俯冲带后撤,产生3—4km厚的岩浆混染地壳,密度为2.9g/cm~3。分析认为受板块运动和弧后扩张影响,沿布兰斯菲尔德海峡盆地扩张脊分布的海底火山裂隙式喷发,并进一步导致盆地的持续性扩张。 相似文献
9.
小波分析与解析延拓方法相结合研究东海深部构造 总被引：3，自引：0，他引：3
东海是环太平洋活动构造带的重要组成部分,是探讨西太平洋边缘及边缘海形成演化的重要窗口。向上延拓主要用来削弱局部异常,突出深部异常,小波分析是重磁场位场分解的有效工具,不仅能提取深部异常,还能更好地将区域异常和局部异常分离。本文利用东海及邻域最新的布格重力异常数据资料,将小波分析与解析延拓方法相结合,分析对比向上延拓20 km的布格重力异常结果与小波分析4阶逼近布格重力异常结果,结合东海及邻域莫霍面的深度,对重力场及莫霍面深度进行初步研究。其中小波4阶逼近结果代表莫霍面形态,小波4阶细节结果代表东海及邻域凹陷凸起形态。 相似文献
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11.
Ingi Olafsson Eirik Sundvor Olav Eldholm Kjersti Grue 《Marine Geophysical Researches》1992,14(2):137-162
Analysis in both the x—t and —p domains of high-quality Expanded Spread Profiles across the Møre Margin show that many arrivals may be enhanced be selective ray tracing and velocity filtering combined with conventional data reduction techniques. In terms of crustal structure the margin can be divided into four main areas: 1) a thicker than normal oceanic crust in the eastern Norway Basin; 2) expanded crust with a Moho depth of 22 km beneath the huge extrusive complex constructed during early Tertiary breakup; 3) the Møre Basin where up to 13–14 km of sediments overlie a strongly extended outer part with a Moho depth at 20 km west of the Ona High; and 4) a region with a 25–27 km Moho depth between the high and the Norwegian coast. The velocity data restricts the continent-ocean boundary to a 15–30 km wide zone beneath the seaward dipping reflector wedges. The crust west of the landward edge of the inner flow is classified as transitional. This region as well as the adjacent oceanic crust is soled by a 7.2–7.4 km s–1 lower crustal body which may extend beneath the entire region that experienced early Tertiary crustal extension. At the landward end of the transect a 8.5 km s–1 layer near the base of the crust is recognized. A possible relationship with large positive gravity anomalies and early Tertiary alkaline intrusions is noted. 相似文献
12.
Some seismic refraction observations undertaken during the IGY are reported here together with a summary of other refraction studies carried out within the Transkei Basin, the Mozambique Ridge and the South African continental shelf area.A 2.5 km section of Cretaceous and younger rocks is associated with profiles observed on the continental shelf; directly below this group are rocks with velocities in the range 4.0–5.5 km s-1, probably representatives of the Karroo and Cape supergroups. The basement material velocity variations were from 5.3 to 6.5 with an average of 5.9 km s-1, and is correlated with granite or Malmesbury Formation plus granite. This crustal structure is similar to that found on the eastern continental shelf of southern South America.The profiles in the Transkei Basin show a thick layer of sediment with velocity range 1.50 to 3.50 km s-1, underlain by a refracting layer in which the average velocity is 4.5 km s-1. The velocity of 6.6 km s-1 obtained for the oceanic layer is similar to the velocities of the crustal layer measured in the Argentine Basin. The mantle velocity (8.1 km s-1) is consistent with the average mantle velocity for the Indian Ocean but significantly lower than the Pacific Ocean average of 8.20 km s-1. The depth to Moho is about 12.0 km and the crustal section is typical oceanic. A plate tectonic model of the early opening of the South Atlantic is used to describe the evolution of the Transkei Basin.On the Mozambique Ridge the thin sediments (0.7 km) are underlain by rocks with velocities averaging 5.6 km s-1. This is more than 1.0 km s-1 faster than the velocity for layer 2 from the Transkei Basin and the Agulhas Plateau, indicating rocks of a younger age or of a different type. Moreover the crustal section of the Ridge has a thickness in excess of 22 km and is in isostatic equilibrium when compared with the adjacent Transkei Basin and Agulhas Plateau. DSDP site 249, situated on the Ridge, penetrated basalt at a depth of 0.4 km. Whether this is continental or oceanic basalt is not known; when this site 249 basalt was compared to the cored basalts of the adjacent Mozambique Basin, inconclusive results were obtained. The essential constitution of the Mozambique Ridge remains an enigma, but solution of this problem is vital for the proper understanding of the Mesozoic history of this oceanic region. 相似文献
13.
Hiroshi Ichikawa Hirohiko Nakamura Ayako Nishina Masataka Higashi 《Journal of Oceanography》2004,60(2):351-363
To better understand the mechanism underlying the variation of the Kuroshio south of central Japan, we have examined the variability
of current structure in its upstream region, southeast of Amami-Ohshima Island in the northern Ryukyu Islands. By combined
use of ship-mounted Acoustic Doppler Current Profiler (ADCP) and the TOPEX/POSEIDON satellite altimeter data on Path 214,
the sea surface absolute geostrophic currents were estimated every ten days from January 1998 to July 2002. The 4.5-year mean
surface current was found to flow northeastward north of 26.8°N with a maximum speed of 14 cm s−1 over the shelf slope at 3000 m depth. The moored current-meter observations at three or four mooring stations from Dec. 1998
to Oct. 2002 suggested the existence of a northeastward undercurrent with a maximum core velocity of 23 cm s−1 at 600 m depth over the shelf slope at 1600 m depth. The mean volume transport in the top 1500 m between 27.9°N and 26.7°N
is estimated to be 16 × 106 m3s−1 northeastward, including the subsurface core current related component of 4 × 106 m3s−1.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Based on the surface drifters that moved out from the Sea of Okhotsk to the Pacific, the surface velocity fields of mean,
eddy, and tidal components in the Oyashio region are examined for the period September 1999 to August 2000. Along the southern
Kuril Island Chain, the Oyashio Current, having a width of ∼100 km, exists with velocities of 0.2–0.4 m s−1. From 40°N to 43°N, the Subarctic Current flows east- or northeastward with velocities of 0.1–0.3 m s−1, accompanied by a meandering Oyashio or Subarctic front. Between the Oyashio and Subarctic current regions, an eddy-dominant
region exists with both cyclonic and anticyclonic eddies. The existence of an eastward flow just south of Bussol' Strait is
suggested. The 2000 anticyclonic warmcore ring located south of Hokkaido was found to have a nearly symmetric velocity structure
with a maximum velocity of ∼0.7 m s−1 at 70 km from the eddy center. Diurnal tidal currents with a clockwise tidal ellipse are amplified over the shelf and slope
off Urup and Iturup Islands, suggesting the presence of diurnal shelf waves. From Lagrangian statistics, the single-particle
diffusivity is estimated to be ∼10 × 107 cm2s−1. 相似文献
16.
The petrophysical properties of sediment drill core samples recovered from the Sardinian margin and the abyssal plain of the
Southern Tyrrhenian Basin were used to estimate the downhole change in porosity and rates of deposition and mass accumulation.
We calculated how the deposited material has changed its thickness as a function of depth, and corrected the thickness for
the compaction. The corresponding porosity variation with depth for terrigenous and pelagic sediments and evaporites was modelled
according to an exponential law. The mass accumulation rate for the Plio-Quaternary is on average 4.8×104 kg m−2 my−1 on the Sardinian margin and for the Pliocene in the abyssal plain. In the latter area, the Quaternary attains its greatest
thickness and a mass accumulation rate of 11–40×104 kg m−2 my−1. The basement response to sediment loading was calculated with Airy-type backstripping. On the lower part of the Sardinian
margin, the basement subsidence rate due to sediment loading has decreased from a value of 300 m my−1 in the Tortonian and during the Messinian salinity crisis (7.0–5.33 Ma) to about 5 m my−1 in the Plio-Quaternary. In contrast, on the abyssal plain this rate has changed from 8–50 m my−1 during the period 3.6–0.46 Ma, to 95–130 m my−1 since 0.46 Ma, with the largest values in the Marsili Basin. The correlation between age and the depth to the basement corrected
for the loading of the sediment in the ocean domain of the Tyrrhenian Basin argues for a young age of basin formation. 相似文献
17.
The circulation of intermediate and deep waters in the Philippine Sea west of the Izu-Ogasawara-Mariana-Yap Ridge is estimated
with use of an inverse model applied to the World Ocean Circulation Experiment (WOCE) Hydrographic Program data set. Above
1500 m depth, the subtropical gyre is dominant, but the circulation is split in small cells below the thermocline, causing
multiple zonal inflows of intermediate waters toward the western boundary. The inflows along 20°N and 26°N carry the North
Pacific Intermediate Water (NPIW) of 11 × 109 kg s−1 in total, at the density range of 26.5σθ–36.7σ2 (approximately 500–1500 m depths), 8 × 109 kg s−1 of the NPIW circulate within the subtropical gyre, whereas the rest is conveyed to the tropics and the South China Sea. The
inflow south of 15°N carries the Tropical Salinity Minimum water of 35 × 109 kg s−1, nearly half of which return to the east through a narrow undercurrent at 15–17°N, and the rest is transported into the lower
part of the North Equatorial Countercurrent. Below 1500 m depth, the deep circulation regime is anti-cyclonic. At the density
range of 36.7σ2, – 45.845σ4 (approximately 1500–3500 m depths), deep waters of 17 × 109 kg s−1 flow northward, and three quarters of them return to the east at 16–24°N. The remainder flows further north of 24°N, then
turns eastward out of the Philippine Sea, together with a small amount of subarctic-origin North Pacific Deep Water (NPDW)
which enters the Philippine Sea through the gap between the Izu Ridge and Ogasawara Ridge. The full-depth structure and transportation
of the Kuroshio in total and net are also examined. It is suggested that low potential vorticity of the Subtropical Mode Water
is useful for distinguishing the net Kuroshio flow from recirculation flows.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
Pan Jiayi Wang Junqin Wang Yanfeng Zhang Xinmei Yuan Yeli Zheng Quan''an 《海洋学报(英文版)》1999,18(4):523-533
INTRODUCTIONThegeoidistheiargeopotentials~econfidingmostlywiththemeanseasurfaceandisdenotedastheheightrelativetotheidealelliPSes~eoftheearth.Thegeoidundulationsinglobalaceareupto100m.TheunevenstructureOftheearthgivesrisetotheunevenfeatureofthecitysot... 相似文献