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1.
A newly discovered area of mud volcanism, about 170 km south of Crete, in the central–eastern part of the Mediterranean Ridge,
was named the “United Nations Rise” (UNR). A survey of the UNR area with the deep-towed ORE tech side-scan sonar equipped
with a subbottom profiler revealed the presence of some mud volcanoes and also showed various other sea-floor features, including
slumps, escarpments and pockmark-type depressions. Several of our interpretations were ground-truthed by coring. The UNR area
appears to belong to the Inner deformation front of the Mediterranean Ridge. 相似文献
2.
The detailed seismic refraction investigation of the oceanic crust south of Shatsky Rise in the Northwestern Pacific revealed
a low velocity zone (LVZ) with an average compressional wave velocity of 6.3 km/s within layer 3. This conclusion is based
on the shadow zone for refractions on the travel time curves in their first arrivals from the M discontinuity. The LVZ may
be composed of oceanic plagiogranites because serpentinization of peridotites would probably lead to an increase in crustal
block volume with a concomitent decrease in density and thereby thickening and upwelling at the place of now “overdeepened”
ocean would be expected. 相似文献
3.
Abstract A giant submarine slump, encompassing a 91‐km by 26‐km block, occurring on the continental slope offshore Iquique, Chile, was identified during a SeaMARC II survey. Utilizing SeaMARC II side‐scan imagery, bathymetry, and seismic reflection data, five morphostructural zones of the slump were identified: the fissured zone, scar zone, tensional depression, central block, and front zone. The fissured zone was developed on the crown of the slump; the scar zone is characterized by scars with the crescent‐shaped slip surfaces and throws ranging from 200 m to 50 m. The tensional depression zone is marked by an area voided by mass slumping, while the central block morphology was formed by uplift. The front zone is comprised of both compressional and tensional subzones. The compressional subzone is characterized by a relative topographic low, on the middle slope, whereas the extensional subzone is characterized by a convex pattern of alternated ridges and hollows, which may represent the debris of the slump on the lower slope. The formation of the slump was strongly influenced by the subduction of the Nazca plate beneath the Chile continental margin, which resulted in the subsidence of the continental slope with a resultant increase in the slope gradient and pore‐water pressure in the sedimentary layers. Slump formation was further facilitated by the development of a complex fault system associated with the subduction and by the triggering effect of earthquakes in the area. 相似文献
4.
Alexander B. Rabinovich Richard E. Thomson Steven J. Bograd 《Journal of Oceanography》2002,58(5):661-671
Hydrographic surveys and satellite imaging reveal that mesoscale anticyclonic (AC) eddies are common features of the area
south of Bussol' Strait, the deepest of the Kuril straits connecting the western North Pacific and Sea of Okhotsk. To examine
the velocity structure of these eddies, we deployed groups of 15-m drogued satellite-tracked surface drifters over the Kuril-Kamchatka
Trench in the fall of 1990 and late summer of 1993. Drifters in both groups entered large AC eddies centered over the axis
of the trench seaward of Bussol' Strait and subsequently underwent a slow northeastward translation. One drifter (Drifter
1315) deployed near the center of the “Bussol' eddy” in 1990, remained in the eddy for roughly 45 days and made five loops
at successively greater distances from the eddy center. Large-amplitude (80–100 cm/s) storm-generated inertial oscillations
were observed during the first two loops. The vorticity field associated with the eddy resulted in a Doppler “red-shift” of
inertial frequency motions such that the “effective” inertial period of 21 hours was roughly 4 hours greater than the nominal
inertial period for the drifter latitude (45°N). In 1993, a second drifter (Drifter 15371) was retained in the Bussol' eddy
for about 40 days. This eddy had characteristics similar to those of the 1990 eddy but was devoid of significant high-frequency
motions until the drifter's final half loop. The observed spatial scales, persistence, and slow poleward translation of the
eddies suggests that they play an important role in the dynamics of the East Kamchatka and Oyashio current systems.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
Three ARGOS drift buoys were deployed in the Oyashio Current off the Kuril Islands near 45°N in fall, 1990, during a joint
Russia/Canada study of western boundary current dynamics in the Subarctic Pacific Ocean. We here report on one buoy deployed
within an anticyclonic warm core ring (WCR86B) which shows evidence of large amplitude inertial motions of near-diurnal frequency.
During its first week within the ring the buoy drifted with a mean azimuthal current speed of 0.40–0.45 m s−1 and a radius of rotation of 15–20 km. However, superimposed on the mean rotation of the ring at this time were “loops” of
near-diurnal period, radius 7–8 km and speeds exceeding 1 m s−1. During successive rotations the buoy spiraled outward, its mean period of rotation increased and the amplitude of the near-diurnal
motions decreased. The large motions are explained by inertial wave trapping and amplification within the extremely large
and weakly stratified eddy, wherein the negative vorticity of the eddy reduces the local inertial frequency to near-diurnal
frequency. We here suggest that either tidal or wind forcing may generate these high-amplitude “loop” motions.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
During the concentrated observation (April–May 1988) conducted as a part of the Ocean Mixed Layer Experiment (OMLET) in the
sea area south of Japan, a conspicuous outbreak of warm water occurred from the large-meander region of the Kuroshio toward
the southwest in the direction of the former Ocean Weather Station “T”. A series of NOAA-AVHRR infrared images clearly showed
the process of this event. A surface buoy-mooring system deployed in this experiment recorded the arrival of this outbreak
of water, in terms of the rise of sea-surface temperature (SST) of 1.5°C and the flow of warm water of 1.5kt toward the northwest
at “T”. We studied this phenomenon by combining time series of infrared SST images with the oceanographic data obtained by
two research vessels. The warm water was about 100 m deep in the section at 137°E along the edge of the Off-Shikoku Warm Water.
It was estimated that about twenty outbreaks of this kind in a year can compensate a large heat loss to the atmosphere above
this ocean region. 相似文献
7.
A proxy named “upwelling age”, defined as the ratio of wind time scale to “advection time”, was developed to quantify the
local tendency for coastal upwelling. The formulation of the “advection time” was derived from Ekman theory. A 3D numerical
model was used to validate and refine the theoretical formula by simulating a total of 30 cases of different bottom topographies
and wind stresses. The results agree reasonably well with the theoretical formulation although some modifications are necessary.
The final formulation of the “advection time” was parameterized as a function of pycnocline depth, bottom slope, and wind
stress. 相似文献
8.
E. L. Vinogradova P. N. Makkaveev Z. G. Melnikova Yu. R. Nalbandov P. A. Stunzhas P. V. Khlebopashev 《Oceanology》2011,51(5):796-803
The Volga River discharge consists of the waters transferred by fast currents through channels and the waters which are passing
through the shallow areas of the delta overgrown by cane. Using the hydrochemical data, it is possible to track distribution
of the waters modified by “biofilters” of macrophytes in the delta shallows starting from the external edge of the delta.
The main distinctive features of these waters are the high content of dissolved oxygen, the abnormally high values of the
pH, and the low content of dissolved inorganic carbon (both total and as CO2). These waters extend in the shape of 1 to 3-km-wide strips at a distance of 20–40 km from the outer border of the delta.
The analysis of the data obtained during the expeditions run by the Institute of Oceanology of the Russian Academy of Sciences
in 2003–2009, along with archived and published data, show that such “modified” waters occur almost constantly along the outer
edge of the Volga River delta. 相似文献
9.
Hurricanes David (August 29–30, 1979) and Frederick (September 2–5, 1979) caused major flooding of the Rio de La Plata in
northern Puerto Rico. A thin mud layer was deposited across the narrow insular shelf adjacent to the river mouth. Within 5
months, fair-weather shelf-winnowing processes moved the mud layer entirely from the shelf, 0.5 to 2 km to the shelf break
at the 50-m contour and beyond. The process of mud movement is termed “mud hopping.” 相似文献
10.
The underwater vocalizations of the beluga whale summering in Onega Bay (64°24′N, 35°49′E) were recorded in June–July of 2008.
The vocalizations were classified into five major whistle types, four types of pulsed tones, click series, and noise vocalizations.
To determine the relationship between the behavioral activity and the underwater vocalizations, a total of fifty-one 2 minute-long
samples of the audio records were analyzed in the next six behavioral contexts: directional movements, quiet swimming, resting,
social interactions, individual hunting behavior, and the exploration of hydrophones by beluga whales. The overall vocalization
rate and the percentage of the main types of signals depend on the behavior of the belugas. We suggest that one of the whistle
types (the “stereotype whistle”) is used by belugas for long-distance communications, while other whistle types (with the
exception of “squeaks”) and three types of pulsed tones (with the exception of “vowels”) are used for short distance communication.
The percentage of “squeaks” and “vowels” was equally high in all the behavioral situations. Thus, we assume that “squeaks”
are contact signals. “Vowels” have a specific physical structure and probably play a role in identification signals. A high
rate of the click series was observed in the process of social interactions. 相似文献
11.
We analyze errors in the global bathymetry models of Smith and Sandwell that combine satellite altimetry with acoustic soundings
and shorelines to estimate depths. Versions of these models have been incorporated into Google Earth and the General Bathymetric
Chart of the Oceans (GEBCO). We use Japan Agency for Marine-Earth Science and Technology (JAMSTEC) multibeam surveys not previously
incorporated into the models as “ground truth” to compare against model versions 7.2 through 12.1, defining vertical differences
as “errors.” Overall error statistics improve over time: 50th percentile errors declined from 57 to 55 to 49 m, and 90th percentile
errors declined from 257 to 235 to 219 m, in versions 8.2, 11.1 and 12.1. This improvement is partly due to an increasing
number of soundings incorporated into successive models, and partly to improvements in the satellite gravity model. Inspection
of specific sites reveals that changes in the algorithms used to interpolate across survey gaps with altimetry have affected
some errors. Versions 9.1 through 11.1 show a bias in the scaling from gravity in milliGals to topography in meters that affected
the 15–160 km wavelength band. Regionally averaged (>160 km wavelength) depths have accumulated error over successive versions
9 through 11. These problems have been mitigated in version 12.1, which shows no systematic variation of errors with depth.
Even so, version 12.1 is in some respects not as good as version 8.2, which employed a different algorithm. 相似文献
12.
A. Baltzer B. Tessier H. Nouzé R. Bates C. Moore D. Menier 《Marine Geophysical Researches》2005,26(2-4):235-245
The presence of gas is a common feature in many seismic sections. However, the origin of the gas is often difficult to determine.
Recently acquired very high resolution seismic profiles using an IKB Seistec boomer provide useful insight to the understanding
of the gas origins in a range of environmental settings including sea lochs and coastal lagoons. The gas features are described
both from a qualitative point of view through their acoustic facies, and quantitatively through the associated seismic signal
(polarisation, amplitude). Acoustic facies include acoustic turbidity, gas “curtains” and “blankets” as well as “white fringes”
and “black shadows”. All the features encountered have been related to specific gas nature generated by different sources
(organic matter degradation in paleo-valley infillings, waste material effluent). 相似文献
13.
The processes underlying the development of the Kuroshio large meanders that occurred in 1986 and 1989 are investigated using
a satellite SST data set and hydrographic data. In both processes visible on the satellite SST images, a round-shaped, lower
SST region with a diameter of about 200 km is found to the east of the Kuroshio small “trigger” meander (Solomon, 1978) until
the region became extinguished near theEnshu Nada. The lower SST region can be interpreted as an anti cyclonic eddy, mainly because of the existence of a warm water mass in
the subsurface layer of this region. The warm water mass is characterized by a constant temperature of 18–19°C, the maximum
thickness of which is about 400 m. The satellite images show that the eddy is closely related to the Kuroshio path transforming
into a shape like the letter “S”. This means that the eddy plays an important role in the development of the Kuroshio large
meander since this, too, tends to follow an “S”-shaped path. Added to this, the subsurface layer structure of the eddy is
similar to that of the warm water mass offShikoku. This similarity, together with the eddy behavior visible on the satellite SST images, implies that the examined eddy corresponds
to the warm water mass offShikoku. In other words, the warm water mass offShikoku can be advected near to theEnshu Nada when the Kuroshio large meander occurs. 相似文献
14.
The sedimentary infill of the Bay of Biscay off Ireland, UK, France and Spain took place in four phases. The last one (35 Ma to present) is characterised by gravitational, pelagic, contouritic and glacigenic processes leading to the setup of three deep sea systems. To the North, the Celtic and Armorican fans are fed by a “canyon-dominated” margin and its connection with the “Manche” palaeoriver, which drained a large area of western Europe. To the South, the Cap-Ferret fan results from the evolution of a “tectonic-dominated” margin and the erosion of the Pyrenee mountains. 相似文献
15.
This study applies modern seismic geomorphology techniques to deep-water collapse features in the Orange Basin (Namibian margin, Southwest Africa) in order to provide unprecedented insights into the segmentation and degradation processes of gravity-driven linked systems. The seismic analysis was carried out using a high-quality, depth-migrated 3D volume that images the Upper Cretaceous post-rift succession of the basin, where two buried collapse features with strongly contrasting seismic expression are observed. The lower Megaslide Complex is a typical margin-scale, extensional-contractional gravity-driven linked system that deformed at least 2 km of post-rift section. The complex is laterally segmented into scoop-shaped megaslides up to 20 km wide that extend downdip for distances in excess of 30 km. The megaslides comprise extensional headwall fault systems with associated 3D rollover structures and thrust imbricates at their toes. Lateral segmentation occurs along sidewall fault systems which, in the proximal part of the megaslides, exhibit oblique extensional motion and define horst structures up to 6 km wide between individual megaslides. In the toe areas, reverse slip along these same sidewall faults, creates lateral ramps with hanging wall thrust-related folds up to 2 km wide. Headwall rollover anticlines, sidewall horsts and ramp anticlines may represent novel traps for hydrocarbon exploration on the Namibian margin.The Megaslide Complex is unconformably overlain by few hundreds of metres of highly contorted strata which define an upper Slump Complex. Combined seismic attributes and detailed seismic facies analysis allowed mapping of headscarps, thrust imbrications and longitudinal shear zones within the Slump Complex that indicate a dominantly downslope movement of a number of coalesced collapse systems. Spatial and stratal relationships between these shallow failures and the underlying megaslides suggest that the Slump Complex was likely triggered by the development of topography created by the activation of the main structural elements of the lower Megaslide Complex.This study reveals that gravity-driven linked systems undergo lateral segmentation during their evolution, and that their upper section can become unstable, favouring the initiation of a number of shallow failures that produce widespread degradation of the underlying megaslide structures. Gravity-driven linked systems along other margins are likely to share similar processes of segmentation and degradation, implying that the megaslide-related, hydrocarbon trapping structures discovered in the Namibian margin may be common elsewhere, making megaslides an attractive element of deep-water exploration along other gravitationally unstable margins. 相似文献
16.
Index and Composites of the Kuroshio Meander South of Japan 总被引:1,自引:0,他引:1
Nikolai Maximenko 《Journal of Oceanography》2002,58(5):639-649
Using the merged NOAA National Oceanographic Data Center (NODC)/Japan Oceanographic Data Center (JODC)/Marine Information
Research Center (MIRC) historical hydrographic dataset, a new Kuroshio large meander (LM) index is introduced. This index
helps to distinguish between the LM events and other types of Kuroshio Current (KC) variability south of Japan. Observations,
re-systematized according to the index, provide composite patterns of typical formation and decay of the LM. The patterns
reveal a remarkable similarity between individual LMs and support the deterministic rather than the stochastic model of LM
evolution on a time-scale of one year. A “trigger” meander (TM) occurs on composite maps six months prior to the LM formation
as a 1° latitude southward shift of the KC axis south of Kyushu. When propagating eastward along the coast of Japan, TM gradually
increases in area. In principal the emergence of LM takes only one month. East of TM and LM a remarkable onshore shift of
the KC is noticed, supplying the coastal region with warm water. Other warm anomalies are found on the warm side of KC next
to the propagating TM and in the larger warm eddy area southeast of Kyushu. Different LMs survive for different times and
decay in some months after KC “jumps” across the Izu Ridge. Changes of water properties on isopycnals in the interior of LM
can be roughly described by two-layer kinematics with an interface at σθ = 27 which suggests a strong inflow of deep Kuroshio waters into the LM core during the formation of the latter.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
A. K. Ambrosimov D. A. Ambrosimov P. N. Makkaveev Yu. R. Nalbandov L. E. Skibinskii P. V. Hlebopashev 《Oceanology》2009,49(5):630-642
Characteristics of different types of river drainage were obtained during studies of a polygon in the near-mouth part of the
Volga River in 2000–2003: “fast” (flowing through deep channels) and “slow” (that which passes through the littoral parts
of the delta (1–2 m)). The low current velocities (lower than in the channel waters by a factor of ten), the abundance of
water vegetation, and the strong heating of the waters lead to the high intensity of the biochemical processes. Therefore,
the chemical composition of the waters is subjected to significant transformation with intensity so high that it allows comparing
these regions with some sort of “bioreactor.” These changes influence the dissolved oxygen and various forms of carbon content. 相似文献
18.
Douglas N. Lambert Peter A. Rona Richard H. Bennett John W. Kofoed 《Geo-Marine Letters》1981,1(1):69-72
Two pendulum-type inclinometers, providing accurate direct measurements of seafloor gradient from a submersible, were developed
and field tested. A manipulator-held inclinometer was used in Great Abaco Canyon to measure the angle of repose of taluslike
carbonate deposits on the canyon wall. A submersiblemounted inclinometer continuously measured, and a camera recorded, variations
in seafloor gradient on the lower continental slope off Cape Hatteras. This area has been previously identified seismically
as containing rotational slump blocks. Slump deposits were found to have slopes of up to 10° while their associated slump
scarps had gradients between 30 and 50°. 相似文献
19.
Bathymetry enhancement by altimetry-derived gravity anomalies in the East Sea (Sea of Japan) 总被引:1,自引:0,他引:1
Kwang Bae Kim Yu-Shen Hsiao Jeong Woo Kim Bang Yong Lee Yi Kyun Kwon Chang Hwan Kim 《Marine Geophysical Researches》2010,31(4):285-298
The gravity-geologic method (GGM) was used to enhance the bathymetry of the East Sea (Sea of Japan) with satellite altimetry-derived
free-air gravity anomalies and shipborne depth measurements. By comparison with the bathymetry model of Smith and Sandwell’s
(SAS) approach (1994), GGM was found to have an advantage with short wavelength (≤12 km) components, while SAS better predicts
longer wavelength (≥25 km) components, despite its dependency on density contrast. To mitigate this limitation, a tuning density
contrast of 10.25 g/cm3 between seawater and the seafloor was primarily estimated by the downward continuation method and then validated by the check
points method with GGM. Similarly, SAS is limited by the “A” value in low-pass part of the Wiener filter, which defines the effective range of the wavelength components on bathymetry.
As a final result, we present an enhanced GGM bathymetry model by integrating all available data. 相似文献
20.
A. S. Samodurov V. Z. Dykman V. A. Barabash O. I. Efremov A. G. Zubov O. I. Pavlenko A. M. Chukharev 《Physical Oceanography》2005,15(5):311-322
We describe a new measuring complex aimed at the investigation of small-scale processes in the upper active layer of the sea.
The necessity of creation of a complex of this sort is justified and a circle of problems that can be solved with the help
of this complex is described. The scales of resolution of horizontal and vertical inhomogeneities in measuring in the mode
of vertical probing are theoretically estimated. The basic technical characteristics of the complex are presented. We also
present the results of laboratory and field tests, which confirm the agreement between the calculated and actual technical
possibilities of the complex. The structural features of various versions of the “Sigma-1” measuring complex (the “Sigma-1P”
point-to-point-operation version and the “Sigma-1Z” probing version) are described.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 5, pp. 60–71, September–October, 2005. 相似文献