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Aleksandre Kandilarov Rolf Mjelde Rolf-Birger Pedersen Bjarte Hellevang Cord Papenberg Carl-Joerg Petersen Lars Planert Ernst Flueh 《Marine Geophysical Researches》2012,33(1):55-76
The Jan Mayen microcontinent was as a result of two major North Atlantic evolutionary cornerstones—the separation of Greenland
from Norway (~54 Ma), accompanied by voluminous volcanic activity, and the jump of spreading from the Aegir to the Kolbeinsey
ridge (~33 Ma), which resulted in the separation of the microcontinent itself from Eastern Greenland (~24 Ma). The resulting
eastern and western sides of the Jan Mayen microcontinent are respectively volcanic and non-volcanic rifted margins. Until
now the northern boundary of the microcontinent was not precisely known. In order to locate this boundary, two combined refraction
and reflection seismic profiles were acquired in 2006: one trending S–N and consisting of two separate segments south and
north of the island of Jan Mayen respectively, and the second one trending SW–NE east of the island. Crustal P-wave velocity
models were derived and constrained using gravity data collected during the same expedition. North of the West Jan Mayen Fracture
Zone (WJMFZ) the models show oceanic crust that thickens from west to east. This thickening is explained by an increase in
volcanic activity expressed as a bathymetric high and most likely related to the proximity of the Mohn ridge. East of the
island and south of the WJMFZ, oceanic Layers 2 and 3 have normal seismic velocities but above normal average crustal thickness
(~11 km). The similarity of the crustal thickness and seismic velocities to those observed on the conjugate M?re margin confirm
the volcanic origin of the eastern side of the microcontinent. Thick continental crust is observed in the southern parts of
both profiles. The northern boundary of the microcontinent is a continuation of the northern lineament of the East Jan Mayen
Fracture Zone. It is thus located farther north than previously assumed. The crust in the middle parts of both models, around
Jan Mayen island, is more enigmatic as the data suggest two possible interpretations—Icelandic type of oceanic crust or thinned
and heavily intruded continental crust. We prefer the first interpretation but the latter cannot be completely ruled out.
We infer that the volcanism on Jan Mayen is related to the Icelandic plume. 相似文献
2.
Vulnerability, hazards and multiple risk assessment for Georgia 总被引：2，自引：1，他引：1
3.
Here, we address the sediment dynamics in the Black Sea based on analysis of remote sensing data from the Medium Resolution
Imaging Spectrometer and numerical simulations with Nucleus for European Modelling of the Ocean model. Boundary conditions
consist of realistic meteorological forcing, including significant wave height generated by wave prediction model. A number
of sensitivity runs was analysed with the aim to find the most suitable parameters governing sediment fluxes. The comparison
between numerical simulations and remote sensing data gives credibility to the quality of simulations. The combined effect
of wind waves and currents in the bed layer controls the sediment resuspension that appears to be the major basin-wide source
of sediment. Sensitivity experiments included or excluded different forcing terms, e.g. sediment flux from rivers enable to
determine the spatial extensions of different point sources. It is concluded that wind-wave forcing is manifested in the sediment
dynamics through episodic high energy events contributing to the increase of horizontal sediment fluxes over the northwestern
shelf. Both satellite images and numerical model simulations demonstrated that the penetration of suspended sediment into
the basin interior was governed by the dynamics of coastal and open-ocean eddies. While fine sediment at sea surface could
cross the continental slope propagating into the open ocean, coarser fractions follow the bottom and their penetration into
the open ocean is limited. The conclusion is thus that the deposition patterns correlate with the specific shape of Black
Sea topography, and the largest depositions are observed in the area of continental slope. 相似文献
4.
Crustal structure of the ultra-slow spreading Knipovich Ridge,North Atlantic,along a presumed ridge segment center 总被引：1，自引：1，他引：0
Aleksandre Kandilarov Hildegunn Landa Rolf Mjelde Rolf B. Pedersen Kyoko Okino Yoshio Murai 《Marine Geophysical Researches》2010,31(3):173-195
A combined ocean bottom seismometer, multichannel seismic reflection and gravity study has been carried out along the spreading
direction of the Knipovich Ridge over a topographic high that defines a segment center. The youngest parts of the crust in
the immediate vicinity of the ridge reveal fractured Oceanic Layer 2 and thermally expanded and possibly serpentinized Oceanic
Layer 3. The mature part of the crust has normal thickness and seismic velocities with no significant crustal thickness and
seismic velocity variations. Mature Oceanic Layer 2 is in addition broken into several rotated fault blocks. Comparison with
a profile acquired ~40 km north of the segment center reveals significant differences. Along this profile, reported earlier,
periods of slower spreading led to generation of thin crust with a high P-wave velocity (Vp), composed of a mixture of gabbro and serpentinized mantle, while periods of faster spreading led to generation of more
normal gabbroic crust. For the profile across the segment center no clear relation exists between spreading rate and crustal
thickness and seismic velocity. In this study we have found that higher magmatism may lead to generation of oceanic crust
with normal thickness even at ultra-slow spreading rates. 相似文献
5.
Crustal structure of the ultra-slow spreading Knipovich Ridge,North Atlantic,along a presumed amagmatic portion of oceanic crustal formation 总被引：4，自引：4，他引：0
Aleksandre Kandilarov Rolf Mjelde Kyoko Okino Yoshio Murai 《Marine Geophysical Researches》2008,29(2):109-134
The ultra-slow, asymmetrically-spreading Knipovich Ridge is the northernmost part of the Mid Atlantic ridge system. In the
autumn of 2002 a combined ocean-bottom seismometer multichannel seismic (OBS/MCS) and gravity survey along the spreading direction
of the Knipovich Ridge was carried out. The main objective of the study was to gain an insight into the crustal structure
and composition of what is assumed to be an amagmatic segment of oceanic crust. P-wave velocity and Vp/Vs models were built
and complemented by a gravity model. The 190 km long transect reveals a much more complex crustal structure than anticipated.
The magmatic crust is thinner than the global average of 7.1 ± 1.0 km. The young fractured portion of Oceanic Layer 2 has
low seismic velocities while the older part has normal seismic velocities and is broken into several rotated fault blocks
seen as thickness variations of Layer 2. The youngest part of Oceanic Layer 3 is also dominated by low velocities, indicative
of fracturing, seawater circulation and thermal expansion. The remaining portion of Layer 3 exhibits inverse variations in
thickness and seismic velocity. This is explained by a sequence of periods of faster spreading (estimated to be up to 8 mm/year
from interpretation of magnetic anomalies) when more normal gabbroic crust was being generated and periods of slower spreading
(5.5 mm/year) when amagmatic stretching and serpentinization of the upper mantle occurred, and crust composed of mixed gabbro
and serpentinized mantle was generated. The volumetric changes and upward fluid migration, associated with the process of
serpentinization in this part of the crust, caused disruption to the overlying sedimentary layers. 相似文献
6.
Aleksandre Kandilarov Kuvvet Atakan Jens Havskov Dragomir Gospodinov 《Bulletin of Earthquake Engineering》2009,7(1):181-198
Plovdiv is the second largest city in the Republic of Bulgaria. A large part of the city is located on Holocene alluvial sediments
and the oldest neighborhoods are situated on syenitic rock outcrops. We believe that local site effects may be an important
contributor to the destruction caused by earthquakes. The primary objective of this study was to estimate quantitatively the
local site effects in the central area of Plovdiv in terms of fundamental site frequency and amplification factor. Another
important objective was to see how these correlate with the geological structures underlying the city. Measurements of the
seismic noise at more than two hundred regularly placed points were made in the central area of the city. The H/V spectra
were then calculated and analyzed to determine the spatial distribution of the fundamental site frequency and the amplification
factor. The results exhibit very good correlation with the local geology. They were also compared with an intensity map from
the strong 1928 Plovdiv earthquake. The comparison clearly demonstrates that the local site effects were the main factor in
the destruction of buildings—the zones where the most damage was observed are also the zones where we have low fundamental
site frequencies and high amplifications. Similarly the areas with high fundamental site frequencies and low amplification
factors cover the neighborhoods where less damage has been observed. This study may form a basis for a more comprehensive
and systematic microzonation study in Plovdiv. 相似文献
7.
In this work, we address the Black Sea setup of Nucleus for European Modelling of the Ocean (NEMO), and in particular some
model enhancements associated with the most important characteristic of ocean dynamics in this semi-enclosed basin, that is
the sea-level variability and its relationship with water cycles and wind. Forcing data are presented in detail and compared
with previously used coarser-resolution data. One emphasis in this paper is on the statistical analyses of forcing data and
outputs from simulations with a focus on the sea level and its change. Numerical simulations are carried out as free run,
and alternatively, altimeter data assimilation based on displacement of water properties in the pycnocline is used. Comparisons
between the two runs identify the robustness of circulation driven by water balance and winter intensification. Problems in
the model to replicate the redistribution of water properties between the two sub-basins in free-run mode are also discussed,
which are observed during years with extreme climatic conditions. 相似文献
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