Micro-bathymetric mapping of the North Alfeo strike-slip fault (offshore Catania Sicily): preliminary results from the FocusX1 expedition

2021 ◽  
Author(s):  
Arnaud Gaillot ◽  
Marc-André Gutscher ◽  
Shane Murphy ◽  
Frauke Klingelhoefer
Keyword(s):  
Fiber Optic ◽  
Video Camera ◽  
Surface Expression ◽  
Relative Displacement ◽  
Fault Scarp ◽  
Linear Feature ◽  
Navigation Data ◽  
Bathymetric Data ◽  
The North ◽  
Summit Region

<p>In October 2020, during the marine expedition FocusX1 onboard the research vessel PourquoiPas? microbathymetric mapping was performed using the ROV Victor6000. The main goal was to map the seafloor expression of the North Alfeo fault and select the best path for deployment of a 6-km long fiber optic strain cable designed to monitor movement along the fault and the deployment sites for 8 geodetic stations.</p><p>Bathymetric data were collected through a Reson Seabat 7125 multibeam echosounder (400 kHz). ROV navigation data were processed using DelphINS, resulting in an optimal merging of navigation sensors (GPS, USBL, DVL, pressure). The MBES data processing (GLOBE software) mainly consisted in estimating and correcting static angular offsets, applying actual in-situ sound speed profile, and finally performing an automatical and manual soundings filtering.</p><p>The resulting bathymetric grid spans a region of roughly 3 km x 1.5 km, with a 1m cell size, and allows  us to identify a variety of morphological features:</p><p>1 - a set of narrow, linear, E-W oriented gulleys, all parallel (not merging/branching) on a regional E dipping 5-15° slope</p><p>2 - a striking, continuous curvi-linear feature, which is interpreted as the primary surface expression of the fault.The fault morphology changes from a smooth less than 10 m depression in the NW to a up to 10-20m high scarp with slopes of 20-30°, and locally sub-vertical cliff faces.</p><p>3 - a local bathymetric plateau (mesa like feature) with a gently E-dipping summit region, showing signs of eastward sliding / rafting tectonics, indicated by N-S oriented gashes/depressions.</p><p>The 3-km long segment of the fault covered by our survey includes the mesa-like bathymetric high (at the NW extremity) interpreted as a transpressional pop-up feature and an elongated, fault bounded trough (at the SE extremity) interpreted as a transtensional pull-apart basin. Video-camera images recorded by ROV Victor6000 from the seafloor provide visual documentation of the fault scarp and seafloor morphology. Future surveys with a sub-bottom profiler and/or HR- seismics can help confirm these interpretations. The ongoing monitoring with the fiber-optic strain cable is being calibrated by a 3-4 year deployment of seafloor geodetic instruments (Canopus acoustic beacons manufactured by iXblue) which started in Oct. 2020, and will allow us to quantify relative displacement across the fault.</p>

scholarly journals The FOCUS experiment 2020 (Fiber Optic Cable Use for Seafloor studies of earthquake hazard and deformation)

2020 ◽  
Author(s):  
Marc-Andre Gutscher ◽  
Jean-Yves Royer ◽  
David Graindorge ◽  
Shane Murphy ◽  
Frauke Klingelhoefer ◽  
...  
Keyword(s):  
Fiber Optic ◽  
Earthquake Hazard ◽  
Test Site ◽  
Relative Displacement ◽  
Integrated System ◽  
Ocean Bottom ◽  
Physics Institute ◽  
The North ◽  
Wide Range ◽  
Laser Reflectometry

<p>Laser reflectometry (BOTDR), commonly used for structural health monitoring (bridges, dams, etc.), for the first time is being tested to study movements of an active fault on the seafloor, 25 km offshore Catania Sicily (an urban area of 1 million people). Under ideal conditions, this technique can measure small strains (10E-6), across very large distances (10 - 200 km) and locate these strains with a spatial resolution of 10 - 50 m. As the first experiment of the European funded FOCUS project (ERC Advanced Grant), in late April 2020 we aimed to connect and deploy a dedicated 6-km long strain cable to the TSS (Test Site South) seafloor observatory in 2100 m water depth operated by INFN-LNS (Italian National Physics Institute). The work plan for the marine expedition FocusX1 onboard the research vessel PourquoiPas? is described here. First, microbathymetric mapping and a video camera survey are performed by the ROV Victor6000. Then, several intermediate junction frames and short connector cables (umbilicals) are connected. A cable-end module and 6-km long fiber-optic strain cable (manufactured by Nexans Norway) is then connected to the new junction box. Next, we use a deep-water cable-laying system with an integrated plow (updated Deep Sea Net design Ifremer, Toulon) to bury the cable 20 cm in the soft sediments in order to increase coupling between the cable and the seafloor. The targeted track for the cable crosses the North Alfeo Fault at three locations. Laser reflectometry measurements began April 2020 and will be calibrated by a three-year deployment of seafloor geodetic instruments (Canopus acoustic beacons manufactured by iXblue) also started April 2020, to quantify relative displacement across the fault. During a future marine expedition, tentatively scheduled for 2021 (FocusX2) a passive seismological experiment is planned to record regional seismicity. This will involve deployment of a temporary network of OBS (Ocean Bottom Seismometers) on the seafloor and seismic stations on land, supplemented by INGV permanent land stations. The simultaneous use of laser reflectometry, seafloor geodetic stations as well as seismological land and sea stations will provide an integrated system for monitoring a wide range of types of slipping events along the North Alfeo Fault (e.g. - creep, slow-slip, rupture). A long-term goal is the development of dual-use telecom cables with industry partners.</p>

scholarly journals Novel Bathymetry of Lake Afdera Reveals Fault Structures and Volcano-Tectonic Features of an Incipient Transform Zone (Afar, Ethiopia)

2021 ◽  
Vol 9 ◽  
Author(s):  
Jean-Charles Schaegis ◽  
Valentin Rime ◽  
Tesfaye Kidane ◽  
Jon Mosar ◽  
Ermias Filfilu Gebru ◽  
...  
Keyword(s):  
Afar Depression ◽  
Nodal Basin ◽  
Bathymetric Data ◽  
The North ◽  
Transfer Zones ◽  
Fault Structures ◽  
Bathymetric Map ◽  
Endorheic Lake ◽  
Tectonic Features ◽  
Transfer Zone

Lake Afdera is a hypersaline endorheic lake situated at 112 m below sea-level in the Danakil Depression. The Danakil Depression is located in the northern part of the Ethiopian Afar and features an advanced stage of continental rifting. The remoteness and inhospitable environment explain the limited scientific research and knowledge about this lake. Bathymetric data were acquired during 2 weeks expeditions in January/February 2016 and 2017 using an easily deployable echosounder system mounted on an inflatable motorized boat. This study presents the first complete bathymetric map of the lake Afdera. Bathymetric results show that the lake has an average depth of 20.9 m and a total volume of 2.4 km3. The maximum measured depth is 80 m, making Lake Afdera the deepest known lake in Afar and the lowest elevation of the Danakil Depression. Comparison with historical reports shows that the lake level did not fluctuate significantly during the last 50 years. Two distinct tectonic basins to the north and the south are recognized. Faults of different orientations control the morphology of the northern basin. In contrast, the southern basin is affected by volcano-tectonic processes, unveiling a large submerged caldera. Comparison between the orientation of faults throughout the lake with the regional fault pattern indicates that the lake is part of two transfer zones: the major Alayta–Afdera Transfer Zone and the smaller Erta Ale–Tat’Ali Transfer Zone. The interaction between these Transfer Zones and the rift axis forms the equivalent of a developing nodal basin which explains the lake’s position as the deepest point of the depression. This study provides evidence for the development of an incipient transform fault on the floor of the Afar depression.

Middle, Upper Jurassic and Lower Cretaceous sedimentary environments of the Djebel Nefusa region, northwestern Libya

1977 ◽  
Vol 8 ◽  
pp. 45-49
Author(s):  
Richard J. Hodgkinson ◽  
Christopher D. Walley
Keyword(s):  
Sedimentary Basin ◽  
Upper Jurassic ◽  
Fault Scarp ◽  
The West ◽  
Sedimentary Environments ◽  
The North ◽  
Clastic Sediments ◽  
Stratigraphic Nomenclature ◽  
Saharan Platform ◽  
North Western

Carbonate and clastic sediments of Jurassic and Cretaceous age are exposed along the fault-scarp of Djebel Nefusa in north-western Libya. Previous geological investigations have been mainly restricted to the eastern sector of the scarp. Recent studies by the authors in the western sector of Djebel Nefusa and on equivalent sediments in southern Tunisia have allowed the first regional interpretation of these rocks.The area studied lies geographically and geologically at the edge of the Saharan Platform, a large cratonic block, composed of rocks of Precambrian-Palaeozoic age. To the north and east lies a downfaulted sedimentary basin (Gabes-Sabratha Basin) containing a large thickness of Mesozoic sediments. The location of the sections measured along Djebel Nefusa are depicted in Fig.1.The stratigraphic nomenclature of the rock succession of Djebel Nefusa was first established in the east and continued laterally towards the west by later workers. Difficulties in the application of this nomenclature are presented by the recognition of facies changes previously overlooked by earlier investigators. However, as a framework for understanding these changes and the sedimentary processes which caused them, the stratigraphy erected by Magnier (1963) is adopted.

The Study of Four-Position North Seeking System under Vibration Environment

2014 ◽  
Vol 668-669 ◽  
pp. 990-993
Author(s):  
Ming Hui Zong ◽  
Deng Hua Li
Keyword(s):  
Fiber Optic ◽  
Reference Signal ◽  
Vibration Signal ◽  
Pi Controller ◽  
Angle Sensor ◽  
The North ◽  
External Reference ◽  
Tilt Sensor ◽  
The Relationship ◽  
Better Than

In order to develop north seeking system with strong anti-interference ability, the influence caused by the swaying base on the performance of north seeker was investigated. The influence of sinusoidal signal of gyros and tilt sensor's output was analyzed based on four-position north seeking system which was consisted of a single axis gyro and a tilt sensor. Fiber optic gyros and tilt sensor are interference by the same vibration signal, according to the relationship between the output signal of gyro and the angle sensor, a PI controller was designed to compensate the gyro's output error. This real time compensation can effectively improve the north seeking accuracy and speed without complicated calculation or external reference signal. The north seeking accuracy is better than 0.03o. Simulation and actual north seeking result proved that this method significantly improves the north seeking performance in vibrant environment.

The Denholm landslide, Saskatchewan. Part I: Geology

1983 ◽  
Vol 20 (2) ◽  
pp. 197-207 ◽  
Author(s):  
E. A. Christiansen
Keyword(s):  
Shear Zone ◽  
Radiocarbon Dating ◽  
Upper Cretaceous ◽  
Average Rate ◽  
Surface Expression ◽  
Recent Time ◽  
Displacement Rate ◽  
The North ◽  
Colorado Group ◽  
Judith River Formation

The Denholm landslide, whose surface is composed of scarps, ridges, and elongated depressions, is 160 m high, 2000 m wide, and up to 100 m thick. The shear zone is in silty, montomorillonitic clay of the upper part of the Lea Park Formation and Upper Colorado Group unit. The Upper Cretaceous Judith River Formation and the Quaternary Empress, Sutherland, and Saskatoon groups were affected by the landslide. Although these sediments were fractured and gravity faulted by tension when the landslide moved, they can be readily traced through the landslide, particularly the upper part. The scarps (gravity faults), ridges (horsts), and elongated depressions (grabens) are the surface expression of tension resulting from the stretching of beds during the landslide.The movement of the landslide is thought to have started when the North Saskatchewan spillway eroded to the level of the present shear zone about 11 000 years ago (established by radiocarbon dating) and is believed to have stopped in recent time. During this time, it moved about 390 m across the North Saskatchewan River alluvium at an average rate of 35 mm per year. As the landslide moved across the valley, it encountered deposition of alluvium at an average rate of about 2.4 mm per year which resulted in the curved shear zone on the alluvium. Keywords: retrogressive landslide, shale-alluvium, displacement, rate, age.

scholarly journals The North Middle Lobe of Centaurus A

2014 ◽  
Vol 10 (S313) ◽  
pp. 246-247
Author(s):  
Susan G. Neff ◽  
Jean A. Eilek ◽  
Frazer N. Owen
Keyword(s):  
Large Scale ◽  
Star Formation Rate ◽  
Formation Rate ◽  
Middle Lobe ◽  
X Ray ◽  
Linear Feature ◽  
The North ◽  
The Galaxy ◽  
Hα Emission ◽  
Centaurus A

AbstractWe present new, deep VLA 327 MHz, GALEX Far-UV, and Hα images of the inner ~50 kpc of Centaurus A. We find the structure identified by Morganti et al. 1999 as a possible “large scale jet” is part of a knotty, linear feature within a broader region of diffuse radio emission. The linear feature is coincident with a narrow ribbon of Far-UV and Hα emission that extends 6-35 kpc from the galaxy core, as well with a similar ridge of soft X-ray emission. The Far-UV image also shows that a strong starburst is occurring in the central dusty disk, with a star-formation rate of ~ 2M⊙ yr−1. We suggest that the various peculiar phenomena seen to the NE of the galaxy can be explained by a wind from the starburst disk, enhanced by energy input from the AGN.

Evidence of recent activity in the Camorro Fault (Central Betics, Southern Spain)

2020 ◽  
Author(s):  
Jorge P. Galve ◽  
Cristina Reyes-Carmona ◽  
Antonio Jabaloy ◽  
Patricia Ruano ◽  
José Vicente Pérez-Peña ◽  
...  
Keyword(s):  
Fault Plane ◽  
Rock Avalanche ◽  
Surface Expression ◽  
World Heritage ◽  
Fault Scarp ◽  
World Heritage Site ◽  
Southern Spain ◽  
Northern Slope ◽  
Human Occupation ◽  
Heritage Site

<p>The Camorro Fault is located at the foot of the northern slope of a limestone karstic massif that is called ‘Sierra de Las Chimeneas’, in the central sector of the Betic Cordillera (Southern Spain). The fault shows a well-marked surface expression. It is a 6 km-length strike-slip with extensional component fault that forms part of the Torcal Shear Zone. This fault can be continued 7 km eastward along the foot of northern slope of the ‘Torcal de Antequera’ (Málaga), World Heritage Site since 2016. The Camorro fault plane is well-exposed in some sectors while in others, the fault plane has been either affected by karstification processes or partially covered by talus deposits.</p><p>One of the most characteristic geomorphological features of the ‘Sierra de Las Chimeneas’ area is an impressive rock avalanche deposit, covering an area of 2.2 km<sup>2</sup> and for which we estimated a volume of 0.48 Hm<sup>3</sup>. Given the characteristics of the rock avalanche deposit, we consider that it could be triggered by an earthquake on the Camorro Fault. This hypothesis is supported by other investigations that have already referred to quaternary paleoseismicity in this area. Previous archaeological research revealed a period of human occupation in a cave (‘Cueva del Toro’) located in the ‘Torcal de Antequera’ that point out evidences about the occurrence of a cataclysm in the late Copper Age (about 5000 years ago). Other studies have also suggested a possible connection between seismic events and megalith-building near Antequera. Beyond this, an archaeoseismic analysis in the megalithic site of Antequera (also World Heritage Site since 2016) found deformation structures probably linked to oscillations between the megalith orthostats during an earthquake. According to all of mentioned research, the Camorro Fault could be a good candidate to account for such prehistoric earthquake.</p><p>Further geochronological work remains to be done, specially focused on dating (e.g. by cosmogenic isotopes) the fault scarp of the Camorro Fault and the associated rock avalanche deposits. If cosmogenic and archaeological dates coincide, we could attribute all the mentioned observations to an earthquake of severe magnitude in an area where the population ignore that hazard. Thus, we could contribute not only to the history of human occupation of the World Heritage Site but also providing insights into the earthquake recurrence and seismic hazard of the region.</p>

scholarly journals What 2‐D multichannel seismic and multibeam bathymetric data tell us about the North Sumatra wedge structure and coseismic response

Tectonics ◽  
2015 ◽  
Vol 34 (9) ◽  
pp. 1910-1926 ◽  
Author(s):  
M. C. G. Frederik ◽  
S. P. S. Gulick ◽  
J. A. Austin ◽  
N. L. B. Bangs ◽  
Udrekh
Keyword(s):  
Bathymetric Data ◽  
The North ◽  
Wedge Structure ◽  
North Sumatra ◽  
Coseismic Response

The AirScope: A Novel Wireless Laparoscope

2012 ◽  
Vol 6 (4) ◽  
Author(s):  
John Lazarus
Keyword(s):  
Video Transmission ◽  
Fiber Optic ◽  
Video Camera ◽  
Video Monitor ◽  
High Definition ◽  
Experimental Prototype ◽  
Camera Systems ◽  
Wide Angle Lens ◽  
Expected Benefits

The modern laparoscope relies on Hopkins’ glass rod lenses, a fiber-optic light source, a video camera, and external cables. This paper discusses the feasibility of developing an experimental prototype of a completely wireless laparoscope by making use of the latest in electronic and optic miniaturization. Design requirements were defined to mimic a standard 10 mm adult laparoscope. An 8 mm diameter (CMOS) camera was used, which delivered standard definition TV resolution at an image refresh rate of 30 Hz. A wide-angle lens was chosen, and a focusing mechanism was designed. Instead of a fiber-optic cable, illumination was achieved using four miniature LED lights. A 2.4 GHz wireless transmission with adequate range for use in an operating theater was chosen. A wireless receiver on a standard personal computer was used to drive a video monitor using off the shelf image processing software. A built-in rechargeable battery powered the wireless laparoscope. Flicker-free in vitro wireless video transmission was achieved. The laparoscope was made waterproof with a front cover lens and can be gas or chemically sterilized. The prototype laparoscope weights 78 g as compared with 900 g for a typical 10 mm laparoscope, camera, fiber-optic, and camera cables. Drawbacks of the prototype include reduced resolution of the video image as compared to high definition (HD) TV quality available on the most recent commercial camera systems. This experimental prototype has illustrated the feasibility of wireless endoscopy systems. The expected benefits include improved ergonomic maneuverability, reduced weight, and decreased electric power requirements.

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