@ VBPR, Oslo | 2018-10-09
Rachel Barrett's research stay at vbpr (oslo, norway)
Rachel Barrett, ESR 1 | 27-31 August 2018
My project has significantly changed direction since this time last year; with the availability of new, very high resolution data being responsible for the shift. TGS recently collected a high resolution 3D seismic cube which covers part of the Tampen slide in the Norwegian Sea, and I was invited to work on this dataset with Benjamin Bellwald and Sverre Planke at VBPR in Oslo.
Multiple large-scale submarine landslides have been identified on the North Sea Fan; and the timing of the largest four of these slides is thought to be related to glacial-interglacial cycles, with a large slide occurring a few thousand years after the transition to an interglacial [Bryn et al., 2005; Solheim et al., 2005]. The Storegga Slide (with a volume of 3500 km3) is the most recent of these large-scale landslides on the Norwegian continental margin, having occurred ~8 ka (thousand years ago). Tampen, the penultimate slide, is purported to have occurred ~125 ka [Berg et al., 2005; Nygård et al., 2005; Solheim et al., 2005]; however, cores collected from the Aegir Ridge in 2014 indicate that this age model may need to be revised. If so, then the preconditioning and triggering mechanisms of the Tampen slide may also require further consideration.
The main goals of my week-long visit to VBPR were to familiarize myself with the new 3D seismic cube; ascertain how that cube can be correlated with other data that images the Tampen slide; and devise a work plan for this component of my project. The team at VBPR were very welcoming and supportive, and I really enjoyed being integrated into their office for the week. It was a new experience for me to be working alongside others who were (are) simultaneously studying different aspects of the same dataset, and I look forward to working with them more in the coming months!
I am also pleased to say that I learnt from my mistake earlier this year - when I had a short research stay in Malta but was too busy to explore much during the weekend I was there - and made the most of the opportunity to explore Oslo; even joining an informal city tour led by the NGI Norwegian teacher (who is also a part-time tour guide), thanks to an invite from fellow SLATE ESRs Thomas and Matthias who are based at NGI (the Norwegian Geotechnical Institute).References Berg, K., Solheim, A. and Bryn, P. (2005). The Pleistocene to recent geological development of the Ormen Lange area. Marine and Petroleum Geology, 22(1–2 SPEC. ISS.), pp. 45–56. Bryn, P. et al. (2005). Explaining the Storegga Slide. Marine and Petroleum Geology, 22(1–2), pp. 11–19. Nygård et al. (2005). The glacial North Sea Fan, southern Norwegian Margin: architecture and evolution from the upper continental slope to the deep-sea basin. Marine and Petroleum Geology, 22(1–2), pp 71-84. Solheim, A. et al. (2005). The Storegga Slide complex: repetitive large scale sliding with similar cause and development. Marine and Petroleum Geology, 22(1–2), pp. 97–107. Where?
- 27-31 August 2018
Let's get muddy! | 2018-10-09
LAKE LUCERNE FIELD TRIP - LET'S GET MUDDY!
Rachel Barrett (ESR 1) , Thomas Zengaffinen (ESR 14), Matthias Rauter (ESR 15) | @ Lake Lucerne, Switzerland (3 October 2018)
We spent our second annual workshop at EAWAG Kastanienbaum on the edge of Lake Lucerne, Switzerland (see previous posts). One component of this workshop was a field trip, where we split into three groups of five, and studied lacustrine landslides in three separate regions of Lake Lucerne. All the groups spent a day out on the lake collecting cores, 3.5 kHz seismic data and CPT data in their regions of interest, before processing the data and attempting to answer questions about slope stability (Weggis Slide), failure and flow mechanics (Zinnen Slide), the timing and lateral extent of the slide (Kastanienbaum, i.e. "SLATE Slide").
Weggis SlideThomas Zengaffinen ESR 13
In this region, our aim was to assess the sediment stability by getting shear strength profiles of unfailed sediment layers. We began by collecting 3.5 kHz seismic data in the region of interest. This data showed past landslide deposits and unfailed terraces, which could be potential future landslide sediments. After studying the seismic sections, we decided on where to characterise the sediments by taking 1m deep sediment cores and measuring shear strength at about 4m depth. The next step was to open the collected cores, and then describe and interpret the observed layering.
In addition, we did Cone Penetration Tests (CPTs) at regular increments of a few centimeters along the core; the results of which could be converted into measurements of shear strength. This procedure resulted in shear strength profiles of the lake subsurface sediments at our decided spots.
This kind of analysing landslide sediments is not part of my daily work in Oslo. What I am working on in Oslo is simulating the landslide rather than working with sediments itself. Nevertheless, it was a qualitative experience that added to my modelling project. I got a feeling of how the mass of my simulated landslide may look like and how measurements of the slide mass are taken. All in all, this field trip gave me a new point of view of landslides. Working with sediment cores and assessing slope stabilities is a complementary discipline to my modelling project. I now have a broader understanding of my own project, and of the entire SLATE project.
Zinnen SlideMatthias Rauter ESR 14
My group investigated a slope a short distance west of the Weggis slide. The bathymetry of the slope shows multiple slides, presumably dating back to the earthquake of 1601. The slide scars are interrupted by stripes of unfailed sediment, giving the slope the look of battlements/towers (German: Zinnen) in the bathymetry. This particular feature makes the slope very interesting for our investigations. The unfailed areas allow us to investigate the pre-failure situation, layering and, to some extent, shear strength. The failed areas, on the other hand, allow insights into failure mechanisms and flow dynamics. The combination of both unfailed and failed slope areas gives a comprehensive recording of the 1601 landslide event. Furthermore, this slope provides us with valuable information for model validation, as the situation both before and after the event can be reconstructed from sediments.
We took seismic profiles, extracted core samples and performed CPTs in the slide deposit region and also in undisturbed sediments nearby. The results of this survey amazed me, as a model developer who has never been involved in field work; the data gave us a detailed view of undisturbed, compressed and sheared sediments, as well as debris flow and turbidity current deposits. I would never have expected to find such a detailed history of a landslide event in 400 year old sediments.
This experience changed my view on experimental geology substantially and I look forward to recalculate this or a similar event with models that we will develop over the next few years.
SLATE SlideRachel Barrett ESR 1
Our project was structured a little differently to the other two groups, due to only having two surveying vessels available. Consequently, we began the field work component of this workshop with half a day of project planning, before acquiring 3.5 kHz seismic profiles, cores and CPTs, and then processing and analyzing the data.
Our study area was just 300 m offshore from EAWAG at Kastanienbaum. A landslide headwall was evident in the multibeam data (see Figure), but few seismic profiles and no cores or CPT data had been acquired in the area, so the landslide (dubbed "SLATE slide" by our team) was relatively unsurveyed. Our aims were to determine the lateral extent and volume of the slide, find out information about the nature of the basal glide plane, and try to constrain the timing of the slide. With this in mind, we constructed a survey plan for the two half days of data collection.
For me, being involved in the project from the initial planning stage was a really valuable experience. We had identify what our key priorities were, and then had to keep coming back to those while surveying, so as to optimize the time spent collecting data. This was especially important when we began to run out of time while collecting 3.5 kHz data due to over-ambitious planning, and was a great exercise in flexible thinking.
Integrating multiple types of data and approaches is critical to getting the full story in any geological area; and so working with core and CPT data was also a helpful learning exercise for me, because, as for Thomas and Matthias, working with these data is not a regular occurrence.
Designing a survey to investigate a landslide, acquiring data, and processing/analyzing that data in such a short time (only two days when we could have easily used one or two weeks) was definitely an ambitious project; however, I think it is safe to say that all fifteen of us learnt something new or developed a skill/skills, and also enjoyed ourselves during the field work exercise.
Related blog posts from the 'Lake Lucerne Workshop' blog seriesLocation
- EAWAG Kastanienbaum (Lake Lucerne)
@ Victoria, Canada (7-9 May 2018) | 2018-05-28
Review of the 8th International Symposium on Submarine Mass Movements and Their Consequences (ISSMMTC)
Rachel Barrett (ESR1), Tugdual Gauchery (ESR3), Maddalena Sammartini (ESR15) | @ Victoria, Canada (7-9 May 2018)
The 8th International Symposium on Submarine Mass Movements and Their Consequences (ISSMMTC) was hosted in Victoria, Canada this year. This bi-/triannual conference is a great opportunity for scientists who are studying mass wasting events to come together and discuss the latest in this growing field of research, and the small size of the conference (about 100 delegates) makes it easy for students to get involved and get good feedback on their work.
SLATE was well represented with PhD candidates (Rachel Barrett, Tugdual Gauchery, Kate Heerema, Maarten Heijnen and Maddalena Sammartini), Principal Investigators (Sebastian Krastel, Michael Clare and Angelo Camerlenghi), SLATE Project Manager (Jannis Kuhlmann), and SLATE-GEOMAR Project Partner (Morelia Urlaub) all presenting their work.
Here, three of our PhD students discuss their experience at the conference:Rachel Barrett (ESR1)
I presented a poster on my recent work entitled “Towards Semi-Automatic Delineation of Submarine Landslides”, borne out of work that began during my research stay with Aaron Micallef in Malta in January. In the poster, I presented preliminary results for the semi-automatic extraction of the headscarps of the Tuaheni and Valdes landslides (active and passive margin, respectively), using values of curvature and slope. A key goal in semi-automatically delineating submarine landslides is to reduce the visual bias (and consequently, range in the value of subsequently calculated parameters such as runout length and volume) that is innately present when their extent is manually defined.
Presentations and conversations I had during the conference helped to highlight research priorities for the next couple of months, and I left the conference with a clearer understanding of what has already been tested in this field (both successfully and unsuccessfully), as well as with possibilities of future collaborations. Overall, I found the 8th ISSMMTC to be a fantastic learning opportunity, and look forward to the next one in 2020.Tugdual Gauchery (ESR 3)
In May 2018 the 8th ISSMMTC was held in Victoria (BC). After presenting a poster at the EGU in April, the focus on mass wasting and the decrease in the number of participants made this symposium even more interesting and it was also easier to get in contact with other scientists.
The poster I presented “Triggering factors and stratigraphic reconstruction of multi-stage failures in the southeastern slope of the Gela Basin in the Strait of Sicily (Central Mediterranean Sea)”, was the next step of my research project for my PhD conducted at ISMAR-CNR in Bologna (Italy). This conference was a great way to show my work to experts and get to know more people from the offshore mass wasting research community.
It was also a chance to visit this beautiful country and discover new places by participating in field trips organised by the conference. They showed us the best places to see in terms of nature (Saanich inlet; Cathedral Grove, Cypress Mountain, …) and geology (tsunami records in Port Alberni, spits, coastal erosion, Squamish geohazards and emergency planning, mass movements, flood mitigation and marine infrastructure). I also got the chance to hear R. Craig Shipp, who is the principal technical expert in geohazards assessment at Shell International Exploration and Development Company, for the course “Introduction to Geohazards Assessment: An Energy Industry Perspective” organized by the conference and which lasted 2 days. The different types of geohazards, the drilling operations, the seismic data, the geohazards interpretation, the standards, and monitoring were reviewed, analyzed with examples and with the leader’s experience.Maddalena Sammartini (ESR 15)
In May 2018 I participated in the 8th ISSMMTC, the first conference since the start of my PhD in Innsbruck. Since I was presenting both a poster and a paper, it was a challenging but very positive experience.
The paper I presented, “Open-slope, translational submarine landslide in a tectonically active continental margin: the Licosa submarine landslide (South-eastern Tyrrhenian Sea)” (Sammartini et al., This conference), is the result of the internship I completed at the OGS in Trieste, Italy, under the supervision of Dr. Angelo Camerlenghi. In my 15-minute talk I presented the interpretation of bathymetric, seismic and core data of Licosa landslide, which occurred on a very gentle and apparently stable slope approximately 11 ka BP. Our research was aimed at identifying evidence in the regional geological structure for potential slope-failure preconditioning factors and triggering factors.
The poster I presented showed some preliminary results of my PhD, which focuses on building a catalogue of lacustrine landslides worldwide. I applied, in a lacustrine environment, the consistent quantitative-description method outlined by Clare et al. (This conference), showing two outstanding examples from Lake Zurich.
The symposium has been a great occasion to “officially” enter into marine geology research, as well as to meet international colleagues. Furthermore, the interaction with other scientists provided me with a list of other lakes to add to my catalogue of lakes where landslide-related research has been carried out.Location
- Victoria, BC, Canada
- R. Barrett, ESR1 [Poster]
- T. Gauchery, ESR3 [Poster]
- K. Heerema, ESR5 [Poster]
- M. Heijnen, ESR10 [Talk]
- M. Sammartini, ESR15 [Poster]
- M. Sammartini, ESR15 [Talk]
- S. Krastel, PI of ESR1 [Talk]
- M. Clare, PI of ESR10 [Talk]
- J. Kuhlmann, Project Manager [Talk]
- M. Urlaub, Project Partner [Talk]
@ University of Malta (UM), Malta | 2018-04-18
Report on research secondment at the Marine Geology and Seafloor Surveying group of the University of Malta
Rachel Barrett, ESR 1 | 14-27/01/2018
I am a doctoral student within the project SLATE and am based at Christian-Albrechts-University in Kiel, Germany. My research is primarily centred on the quantitative description and analysis of submarine landslides using geophysical and hydroacoustic data. Compared to their terrestrial counterparts, submarine landslides are poorly studied; this is a direct consequence of lower (and more variable) data resolution compared to terrestrial data, and artefacts related to the overlying water column. These factors make quantitative analysis of submarine landslides challenging, and so the majority of studies rely on a qualitative approach. This makes comparison of landslides that are of differing sizes, in different settings or formed by different processes challenging as there is an inherent subjectivity involved in a qualitative approach. Studies have recognized the need for a unifying quantitative framework for the analysis of submarine landslides, with one recent study (Clare et al., 2018) laying out quantitative parameters that should be calculated for submarine landslides. However, if the extent of the landslide is visually delineated, calculation of these quantitative parameters remains non-unique. One goal of my project is to create a routine (using python or GIS software) for the semi-automatic delineation of submarine landslides. This will enable the calculation of a suite of geomorphic parameters (such as displaced volume, runout length, and width) in an objective manner, allowing for easy comparison of landslides of different ages and in varying settings.
Geomorphometric parameters such as slope gradient, profile curvature, aspect and surface roughness are routinely used to describe landforms both onshore and in the marine realm; however the suite of geomorphometric parameters that is used in a marine setting is greatly reduced compared to that utilised onshore. This is a consequence of data resolution and availability, as well as a distinct variation in the geomorphology of the seafloor compared to terrestrial landscapes. A second objective of my research is to explore whether there are additional geomorphometric parameters that are applied in terrestrial settings that could help to provide more information about submarine landslides.
Aaron Micallef is a lecturer at the University of Malta and leads their Marine Geology and Seafloor Surveying group. His research on the Storegga Slide offshore of Norway (e.g. Micallef et al., 2007; 2008) has contributed significantly to the application of geomorphometric parameters for the quantitative description of submarine landslides. The focus of my research stay was to learn from Aaron and to better understand where the gaps in knowledge in the field of quantitative parameterisation of submarine landslides lie. During the two weeks I spent in Malta, we worked on setting up a framework for the duration of my project: considering what questions we hope to answer and how my research can fit in with and complement other, on-going research. We also considered and began work on the task of semi-automatic delineation of submarine landslides. The two weeks in Malta were incredibly useful for refining the direction of my research and I look forward to ongoing collaborations with Aaron.
Clare et al. (2018). A consistent global approach for the morphometric characterization of subaqueous landslides. Geological Society of London, Special Publications, 477, doi: 10.1144/SP477.15
Micallef, A., Berndt, C., Masson, D. G., & Stow, D. A. V. (2007). A technique for the morphological characterization of submarine landscapes as exemplified by debris flows of the Storegga Slide. J. Geophys. Res., 112, 1-15, doi: 10.1029/2006JF000505
Micallef, A., Berndt, C., Masson, D. G., & Stow, D. A. V. (2008). Scale invariant characteristics of the Storegga Slide and implications for large-scale submarine mass movements. Marine Geology, 247, 46-60, doi: 10.1016/j.margeo.2007.08.003Where?