Acoustic Seafloor Geodesy: Strain measurement across the North Anatolian Fault in the Sea of Marmara

Over 70 % of Earth’s surface is covered by water and inaccessible to standard methods of satellite geodesy. The emerging field of seafloor geodesy aims to provide methods to resolve seafloor deformation with high accuracy. In this thesis data from the first GEOMAR Helmholtz Centre for Ocean Research Kiel acoustic network deployment across the North Anatolian Fault in the Sea of Marmara will be analyzed and discussed. The dextral strike-slip fault system has produced a series of large devastating earthquakes over the last century such as the Izmit (Mw 7.6) earthquake in 1999. However, the Istanbul-Silivri fault segment in the Marmara Sea has not ruptured since 1766 and remains in the interseismic phase. The acoustic seafloor geodetic network is designed to measure strain between transponders on the seafloor. The network consists of six autonomous transponders installed on the seafloor and measures sound velocity, tilt, temperature, pressure and time of flight between the transponders. The sound speed sensors show a long term drift resulting in apparent o sets in baselines. Therefore, an approach is developed which uses constant salinity values for the estimation of sound speed. The resolution of a baseline measurements is defined as the standard deviation over time and increases linearly to ranging distance up to 1 km. Synthetic baselines are estimated in order to compare the di erence of baselines calculated using a water column of constant sound velocity gradient with the measured data including spatial heterogeneity along the ray path. About 65 % of the baseline fluctuations are suggested to originate from spatial heterogeneity along the ray path. Time series of 18 months reveal the absence of deformation estimates beneath the geodetic array within the resolution of 5 mm/a. The slip estimate from far field geodetic land stations as well as the absence of deformation from the acoustic geodetic seafloor data indicate that the North Anatolian Fault is highly locked and accumulating strain. The single baseline located in the nework’s west is showing deformation at a rate of 7 mm/a corresponding to the movement of a potential normal fault imaged by AUV Bathymetry

Vorrichtung zur lösbaren Verbindung eines Drahtes und Verfahren zum Ausbringen des Gerätes in ein Gewässer mit der Vorrichtung

Die Erfindung betrifft eine Vorrichtung zur lösbaren Verbindung eines Drahtes, insbesondere eines Tiefseedrahtes (1), mit einem Gerät, insbesondere Tiefseegerät (9), wobei eine Auslöseeinheit (11) zwischen dem Draht (1) und dem Gerät (9) vorgesehen ist, die zum bedarfsweisen Lösen der Verbindung des Drahts (1) mit dem Gerät (9) unter Wasser ausgebildet ist. Erfindungsgemäß sind zumindest ein erster und ein zweiter Transponder (4, 8) vorgesehen, die zwischen dem Draht (1) und der Auslöseeinheit (11) angeordnet sind, wobei der Draht (1) über eine Verbindung mit der Auslöseeinheit (11) verbunden ist und die Verbindung eine definierte Länge aufweist. Des Weiteren betrifft die Erfindung ein Verfahren zum Ausbringen des Gerätes (9) in ein Gewässer, insbesondere in Meerwasser, vorzugsweise in die Tiefsee, mit dieser Vorrichtung

Monitoring submarine fault deformation using direct-path ranging

The seafloor stores crucial information on sub-seafloor processes, including stress, elastic strain, and earthquakes. This information may be extracted through the nascent scientific field of seafloor geodesy. The GeoSEA (Geodetic Earthquake Observatory on the SEAfloor) array uses acoustic signals for direct-path ranging and relative positioning at mm-scale resolution for a period of up to 3.5 years. The transponders also include high-precision pressure sensors to monitor vertical movements and dual-axis inclinometers in order to measure their altitude as well as any change in submarine fault zones and characterizing their behavior (locked or aseismically creeping). A further component of the network is GeoSURF, a self-steering autonomous surface vehicle (Wave Glider), which monitors system health and is able to upload the seafloor data to the sea surface and to transfer it via satellite. Seafloor transponders are currently installed across a dextral strike-slip fault to measure the instability of the eastern flank of Mt Etna in Sicily, along the North Anatolian Fault offshore Istanbul to measure the strain build-up along the fault in a seismic gap. In addition, three arrays are currently deployed on the marine forearc and outer rise of the South American subduction system around 21°S. This segment of the Nazca-South American plate boundary has last ruptured in an earthquake in 1877 and was identified as a seismic gap prior to the 2014 Iquique earthquake (Mw 8.1). The southern portion of the segment remains unbroken by a recent earthquake. The first 12 month of all geodetic installations were analyzed and we discuss baselines with precision less 5 mm for ranges up to 2000 m of distance and compare them to synthetics baselines. The North Anatolian across-fault baseline changes remains within the resolution and preclude fault-displacement rates larger a few millimeters-per-year, which suggests a locked fault zone

Contact geometry modification of friction-welded semi-finished products to improve the bonding of hybrid components

To improve the bond strength of hybrid components when joined by friction welding, specimens with various front end surface geometries were evaluated. Rods made of aluminum AA6082 (AlSi1MgMn/EN AW-6082) and the case-hardening steel 20MnCr5 (AISI 5120) with adapted joining surface geometries were investigated to create both a form-locked and material-bonded joint. Eight different geometries were selected and tested. Subsequently, the joined components were metallographically examined to analyze the bonding and the resulting microstructures. The mechanical properties were tested by means of tensile tests and hardness measurements. Three geometrical variants with different locking types were identified as the most promising for further processing in a forming process chain due to the observed material bond and tensile strengths above 220 MPa. The hardness tests revealed an increase in the steel’s hardness and a softening of the aluminum near the transition area. Apparent intermetallic phases in the joining zone were analyzed by scanning electron microscopy (SEM) and an accumulation of silicon in the joining zone was detected by energy-dispersive X-ray spectroscopy (EDS). © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Neurological outcome after emergency radiotherapy in MSCC of patients with non-small cell lung cancer - a prospective trial

Background: The aim of this trial was to investigate neurological outcome after emergency RT in MSCC of NSCLC patients with acute neurological deficit. Methods This pilot trial was prospective, non-randomized, and monocentre, ten patients were treated from July 2012 until June 2013. After onset of neurological symptoms RT was started within 12 hours. The neurological outcome was assessed at baseline, and six weeks after RT using the ASIA Impairment Scale (AIS). Results: The results showed an improved neurological outcome in one patient (10%), one patient (10%) had a decreased, and five patients (50%) a constant outcome after six weeks. Three patients (30%) died within the first six weeks following RT, additional 4 patients (40%) died within 4 month due to tumor progression. Conclusion: In this group of NSCLC patients we were able to show that emergency RT in MSCC with acute neurological deficit had no considerable benefit in neurological outcome. Therefore, short-course regime or best supportive care due to poor survival should be considered for these patients with additional distant metastases. Patients with favorable prognosis may be candidates for long-course RT. Trial Registration: Clinical trial identifier http://www.clinicaltrials.gov

Salinity and time can alter epibacterial communities of an invasive seaweed

The establishment of epibacterial communities is fundamental to seaweed health, and fitness, in modulating ecological interactions and may also facilitate adaptation to new environments. Few recent studies have investigated the influence of abiotic factors like light, temperature as drivers of epibacterial community composition on seaweeds. Although salinity can determine bacterial abundance, growth and community composition, influence of salinity as a driver of epibacterial community composition (until species level) has not been investigated for seaweeds and especially under long time scales. We also do not know how abiotic stressors may influence the ‘core’ bacterial species of seaweeds. Following an initial (immediately after field collection, T0) sampling of epibacterial community of an invasive red seaweed Agarophyton vermicullophylum, we conducted a long term mesocosm experiment for 5 months, to examine the influence of three different salinities (low, medium and high) at two different time points (T1, T2) on the epibacterial community richness and composition of Agarophyton. Metagenomic sequencing showed that epibacterial communities changed significantly according to salinity and time points sampled. Epibacterial richness was significantly different between low and high salinities at both time points. Epibacterial richness also varied significantly among T1 and T2 within low, medium and high salinity level. Irrespective of salinity levels and time points sampled 727 taxa consistently appeared in all Agarophyton samples hinting at the presence of core bacterial species on the surface of the alga. Our results indicate that both salinity and time can be major driving forces in structuring epibacterial communities of seaweeds with respect to richness and β diversity. We highlight the necessity of conducting long term experiments allowing us to detect and understand epibacterial succession over time on seaweeds