Quest for Fluid Flow along the Gloria Fault – First results of R/V Meteor expedition 162

<p>Vast areas of the deep ocean floor are still insufficiently explored with respect to tectonic processes, exchange processes between the lithosphere and the ocean, and potential deep chemosynthetic energy sources for life. Transform faults and fracture zones, which are dominant seafloor morphological features in the abyssal ocean, deserve specific attention in this regard as they provide potential pathways for fluid recycling. One of them is the Gloria Fault, a unique feature in the Central North Atlantic. It has been the source of large magnitude earthquakes (namely the 1941, M8.4, the second largest instrumental earthquake on a fracture zone) and is a special case of a plate boundary, corresponding to the transform reactivation of an old oceanic fracture zone. Seismic refraction has shown an anomalous layer between normal lower crust and uppermost mantle, possibly a 4 km thick layer of hydrated mantle. We present first results of RV Meteor cruise M162 (March-April 2020) dedicated to the groundtruthing of potential fluid emanation sites.</p>

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Crustal thickness variations between the Greenland and Ellesmere Island margins determined from seismic refraction

Canadian Journal of Earth Sciences ◽

10.1139/e94-124 ◽

1994 ◽

Vol 31 (9) ◽

pp. 1407-1418 ◽

Cited By ~ 15

Author(s):

H. Ruth Jackson ◽

I. Reid

Keyword(s):

Sedimentary Basin ◽

Seismic Refraction ◽

Plate Boundary ◽

Ellesmere Island ◽

North American Plate ◽

Ocean Bottom ◽

Transform Faults ◽

Ocean Bottom Seismometers ◽

Thickness Variations ◽

Thin Crust

Two densely sampled marine refraction lines were shot in northern Baffin Bay on the shelves of Devon and Ellesmere islands (North American plate) and Greenland (Greenland plate). A total of 11 ocean-bottom seismometers recorded the airgun signals. The processed data were analyzed by the use of ray tracing and amplitude modelling. Two-dimensional models were derived that reproduce the characteristics of the observed data. A 5 km deep sedimentary basin was identified on the south end of line 3. On both lines the crustal velocity has a range of 5.7–6.6 km/s. Midway along the line on the shelf of Devon and Ellesmere islands, the Moho shallows abruptly northward from 27 to 20 km. The thinned crust is not overlain by a sedimentary basin to compensate for the elevated Moho, suggesting this is not an extensional feature. The thickness of the crust adjacent to northwest Greenland increases from south (22 km) to north (37 km). The thickening occurs in two stages: a sharp increase in the depth to Moho northwest of the sedimentary basin followed by a gradual deepening to the end of the line. The thin crust on the shelf of Ellesmere Island is located adjacent to the thick crust of Greenland. Plate reconstructions based on regional magnetic anomalies and transform faults indicate that Greenland is a separate plate. The crustal structure revealed by seismic refraction and reflection profiles and the variations in the depth to Moho are consistent with the plate boundary occurring between the refraction lines.

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The GITEWS ocean bottom sensor packages

Natural Hazards and Earth System Science ◽

10.5194/nhess-10-1759-2010 ◽

2010 ◽

Vol 10 (8) ◽

pp. 1759-1780

Author(s):

O. Boebel ◽

M. Busack ◽

E. R. Flueh ◽

V. Gouretski ◽

H. Rohr ◽

...

Keyword(s):

Warning System ◽

Deep Ocean ◽

Indian Ocean Tsunami ◽

False Alarms ◽

Ocean Bottom ◽

Bottom Pressure ◽

Tsunami Early Warning ◽

Ocean Bottom Seismometers ◽

First Results ◽

Sensor Package

Abstract. The German-Indonesian Tsunami Early Warning System (GITEWS) aims at reducing the risks posed by events such as the 26 December 2004 Indian Ocean tsunami. To minimize the lead time for tsunami alerts, to avoid false alarms, and to accurately predict tsunami wave heights, real-time observations of ocean bottom pressure from the deep ocean are required. As part of the GITEWS infrastructure, the parallel development of two ocean bottom sensor packages, PACT (Pressure based Acoustically Coupled Tsunameter) and OBU (Ocean Bottom Unit), was initiated. The sensor package requirements included bidirectional acoustic links between the bottom sensor packages and the hosting surface buoys, which are moored nearby. Furthermore, compatibility between these sensor systems and the overall GITEWS data-flow structure and command hierarchy was mandatory. While PACT aims at providing highly reliable, long term bottom pressure data only, OBU is based on ocean bottom seismometers to concurrently record sea-floor motion, necessitating highest data rates. This paper presents the technical design of PACT, OBU and the HydroAcoustic Modem (HAM.node) which is used by both systems, along with first results from instrument deployments off Indonesia.

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Supporting Wiki-Based Knowledge Exchange Processes

10.31234/osf.io/peq96 ◽

2017 ◽

Author(s):

Sven Heimbuch

Keyword(s):

Knowledge Exchange ◽

Experimental Studies ◽

Future Research ◽

Collaboration Scripts ◽

Group Awareness ◽

Exchange Processes ◽

First Results ◽

Complex Knowledge ◽

Collaborative Knowledge ◽

Quantitative And Qualitative Methods

Complex knowledge exchange processes in collaborative knowledge building settings within wikis can be either supported by providing guidance in form of cognitive group awareness information or by explicitly guiding learners with collaboration scripts. My Ph.D. project comprises a series of three experimental studies to determine which kind of support is most beneficial for varying types of learners working with wikis. For this research different fields of CSCL are integrated and both quantitative and qualitative methods are applied to provide comprehensive analyses in order to provide opportunities for other related research. Presenting and discussing aspects of my research and first results could be beneficial for my future research.

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A comparative study for structural bedrock delineation by using conventional geophysical methods

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.17217 ◽

2001 ◽

Vol 34 (4) ◽

pp. 1301

Author(s):

Τ. Δ. ΠΑΠΑΔΟΠΟΥΛΟΣ ◽

I. A. ΑΛΕΞΟΠΟΥΛΟΣ ◽

Π. Ι. ΚΑΜΠΟΥΡΗΣ

Keyword(s):

Seismic Refraction ◽

Geophysical Methods ◽

Clear Distinction ◽

The Past ◽

Tectonic Processes ◽

Refraction Method ◽

Limestone Bedrock ◽

Modern Analysis ◽

Seismic Refraction Method ◽

Effective Design

In this paper is examined the potential and effectiveness of two conventional geophysical methods in geotechnical research. The seismic refraction method that has been successfully used in the past for subsurface bedrock delineation in foundation projects, failed to indicate clear distinction between flysch and limestone bedrock material in the area under investigation. This failure is due to the macro-anisotropy structure of the limestone that resulted from joints, tectonic processes or/and karstic phenomena and later fillings of the voids with argillaceous material. The geoelectrical method of vertical sounding, on the other hand, although provided a clear distinction for the bedrock characterization, failed to distinguish the overburden cover from the underlain flysch formation. Finally, in this paper it is shown that for a successful application of geophysical work in geotechnical research, it is required effective design, utilization of modern analysis methods and handling more than geophysical methods.

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Evolution of migrating transform faults in anisotropic oceanic crust: examples from Iceland

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2018-0260 ◽

2019 ◽

Vol 56 (12) ◽

pp. 1297-1308 ◽

Cited By ~ 1

Author(s):

Jeffrey A. Karson ◽

Bryndís Brandsdóttir ◽

Páll Einarsson ◽

Kristján Sæmundsson ◽

James A. Farrell ◽

...

Keyword(s):

Plate Boundary ◽

Fault Zones ◽

Plate Boundaries ◽

Transform Fault ◽

Eurasian Plate ◽

Transform Faults ◽

The North ◽

Rift Propagation ◽

Oriented Parallel ◽

Ocean Ridge

Major transform fault zones link extensional segments of the North American – Eurasian plate boundary as it transects the Iceland Hotspot. Changes in plate boundary geometry, involving ridge jumps, rift propagation, and related transform fault zone migration, have occurred as the boundary has moved relative to the hotspot. Reconfiguration of transform fault zones occurred at about 6 Ma in northern Iceland and began about 3 Ma in southern Iceland. These systems show a range of different types of transform fault zones, ranging from diffuse, oblique rift zones to narrower, well-defined, transform faults oriented parallel to current plate motions. Crustal deformation structures correlate with the inferred duration and magnitude of strike-slip displacements. Collectively, the different expressions of transform zones may represent different stages of development in an evolutionary sequence that may be relevant for understanding the tectonic history of plate boundaries in Iceland as well as the structure of transform fault zones on more typical parts of the mid-ocean ridge system.

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Petrology of a transform fault zone and adjacent ridge segments

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1971.0005 ◽

1971 ◽

Vol 268 (1192) ◽

pp. 423-441 ◽

Cited By ~ 122

Keyword(s):

Oceanic Crust ◽

Fault Zone ◽

Fracture Zone ◽

Volcanic Eruptions ◽

Spreading Ridge ◽

Transform Fault ◽

Transform Faults ◽

Near Surface ◽

The North ◽

Transform Fault Zone

The Verna Fracture Zone in the North Atlantic (9 to 11° N), which has been identified as a transform fault zone, contains exposures of serpentinized peridotites, while its adjacent ridge segments are floored mainly by typical abyssal ocean ridge basalts. This petrologic contrast correlates with the greater frequency of volcanic eruptions along the actively spreading ridge segments compared to the transform fault zone. Where rifting components occur across transform faults, exposures of the deeper zone of oceanic crust may result. The bathymetry of the Verna Fracture Zone suggests that some uplift parallel to the fracture zone as well as rifting led to exposures of deeper rocks. The basalts from the adjacent ridge axes contain ‘xenocrysts’ of plagioclase and olivine and more rarely of chromite. These appear to have a cognate origin, perhaps related to cooling and convection in near surface magma chambers. The basalts from the ridge axes, offset and on opposite sides of the transform fault, have similar features and compositions. The plagioclase peridotites have mineralogical features which indicate equilibration in the plagioclase pyrolite facies, suggesting maximum equilibration depths of around 30 km for a temperature of around 1200 °C. The chemical characteristics of the Vema F.Z. peridotites suggest that they may be undifferentiated mantle, emplaced as a subsolidus hot plastic intrusion or as a crystal mush. The abundance of peridotites and serpentinized peridotites is believed to reflect their abundance in seismic layer three of the oceanic crust.

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The significance and tectonic evolution of Huatung basin

10.5194/egusphere-egu2020-4608 ◽

2020 ◽

Author(s):

Minghui Zhao ◽

Jean-Claude Sibuet ◽

Jonny Wu ◽

Longtao Sun ◽

Jiazheng Zhang

Keyword(s):

Seismic Refraction ◽

Plate Boundary ◽

Philippine Sea Plate ◽

Plate Boundaries ◽

Manila Trench ◽

Shear Plate ◽

Second Fracture ◽

Tectonically Active ◽

Seismic Refraction Survey ◽

Early Cenozoic

<p>The Huatung basin (HB), located between the Philippine Sea plate (PSP) and the South China Sea (SCS), has likely existed near tectonically-active plate boundaries since the early Cenozoic. It may record SCS evolution from the SCS rifting phase to today, and is a key region to understand the broad geodynamic interactions between the SCS and PSP. A left-lateral shear plate boundary between the SCS and PSP followed the Gagua ridge and was active before 56 Ma. A slight compressive component along the Gagua ridge might have occurred from 40 to 30 Ma, giving rise to the topographic uplift of Gagua ridge and adjacent ridges with possibly some underthrusting of the PSP below the HB. A significant compressive episode also occurred along a second fracture zone around 23 Ma ago. The Manila trench inception occurred along the PSP-SCS plate boundary before the end of SCS spreading, involving the subduction of the younger SCS beneath the older HB. Later the intra-oceanic Luzon arc formed and collided in a sub-parallel fashion with the Eurasian continent around 5-6 Ma ago to form Taiwan. The PSP/EU motion was oblique with respect to this plate boundary during SCS opening. However, we have no direct evidence of the HB age (early Cenozoic or early Cretaceous) and if the PSP underthrusted below the HB. We propose to carry a deep seismic refraction survey and dredge sampling of basement units to clarify this problem. This work is supported by the Chinese National Natural Science Foundation (contracts 91958212, 41730532, 41576070 and 41676043).</p>

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The Oceanographer fracture zone -- I. Crustal structure from seismic refraction studies

Geophysical Journal International ◽

10.1111/j.1365-246x.1983.tb05007.x ◽

1983 ◽

Vol 75 (3) ◽

pp. 713-736 ◽

Cited By ~ 95

Author(s):

M. C. Sinha ◽

K. E. Louden

Keyword(s):

Crustal Structure ◽

Fracture Zone ◽

Seismic Refraction

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FIRST RESULTS FROM ELECTRICAL AND SEISMIC STUDIES OF LOW‐RESISTIVITY, LOW‐VELOCITY MATERIAL BENEATH EASTERN COLORADO

Geophysics ◽

10.1190/1.1440748 ◽

1977 ◽

Vol 42 (4) ◽

pp. 804-810 ◽

Cited By ~ 3

Author(s):

M. Landisman ◽

W. Chaipayungpun

Keyword(s):

Seismic Refraction ◽

Impedance Tensor ◽

High Plains ◽

Low Velocity ◽

Low Resistivity ◽

Field Recordings ◽

Pierre Shale ◽

West Texas ◽

First Results ◽

Local Water

First results are reported for magnetotelluric (MT) observed apparent resistivities and phases, corresponding to both off‐diagonal components of the 2 by 2 electromagnetic impedance tensor, derived from E and H field recordings near Anton, in the High Plains of eastern Colorado. The data were recorded by a gain ranged, multichannel, multirate digital field system. The results, which span a frequency range of roughly [Formula: see text], extend from about 0.05 sec (20 Hz) to several thousand seconds. Corresponding sets of tightly clustered, practically continuous MT apparent resistivities and phases are virtually identical, constituting strong evidence for lateral homogeneity and isotropy of the electrical conductivity near this site. The derived one‐dimensional resistivity‐depth model is concordant with the depth and thickness of the local water table, with resistivities and depths for the Pierre shale derived from nearby well logs, with reconnaissance audiomagnetotelluric (AMT) data, and with ultra‐long period apparent resistivities derived from regional Deep Geomagnetic Sounding observations. The derived resistivity depth distribution also compares well with the depth to the crystalline basement from the neighboring U.S.G.S. Lamar‐Sterling, Colorado, seismic refraction profile. The concordance, between depths interpreted for a mid‐crustal seismic low‐velocity zone and a corresponding low‐resistivity zone at this site, parallels similar results previously reported for west Texas‐eastern New Mexico, and various sites in the U.S.S.R.

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