“…Further corroborating evidence comes in the form of the sheared section in core CE11_03 that appears as though in situ layers have been locally deformed, possibly due to the lateral pressures emanating from the toe of the slide plowing through the adjacent seafloor. Different scenarios for modeling of Slide C to match the deposits as seen on the bathymetric data reveal that the best fit resulted when a Bigham rheology was adopted with either a velocity-dependent term or with basal frictional properties (Salmanidou et al, 2018).…”
Section: Styles Of Mass Transportmentioning
confidence: 99%
“…Attempts to model the flow behavior of Slides A and B, using the same approach as for slide C, demonstrated that this was not possible and the modeled deposits mapped beyond the actual ones (Salmanidou et al, 2018). This was attributed to potentially different rheological properties (Salmanidou et al, 2018).…”
Section: Styles Of Mass Transportmentioning
confidence: 99%
“…Attempts to model the flow behavior of Slides A and B, using the same approach as for slide C, demonstrated that this was not possible and the modeled deposits mapped beyond the actual ones (Salmanidou et al, 2018). This was attributed to potentially different rheological properties (Salmanidou et al, 2018). Therefore, the assumption that slide events that occur in the same area and as a result should have the same lithological characteristics, and by extension rheological characteristics, is wrong, at least for this case study, as demonstrated by Salmanidou et al (2018) and by the different deposits we find in the cores in this study.…”
One of the most challenging tasks when studying large submarine landslides is determining whether the landslide was initiated as a single large event, a chain of events closely spaced in time or multiple events separated by long periods of time as all have implications in risk assessments. In this study we combine new multichannel seismic profiles and new sediment cores with bathymetric data to test whether the Rockall Bank Slide Complex, offshore western Ireland, is the composite of multiple slope collapse events and, if so, to differentiate them. We conclude that there have been at least three voluminous episodes of slope collapse separated by long periods of slope stability, a fourth, less voluminous event, and possibly a fifth more localized event. The oldest event, Slide A (200 km 3 ), is estimated to be several hundred thousand years old. The second event, Slide B (125 km 3 ), took place at the same location as slide A, reactivating the same scar, nearly 200 ka ago, possibly through retrogression of the scarp. Slide C (400 km 3 ) took place 22 ka ago and occurred further north from the other slides. Slide D was a much smaller event that happened 10 ka ago, while the most recent event, albeit very small scale, took place within the last 1,000 years. This study highlights the need to thoroughly investigate large slide complexes to evaluate event sequencing, as seismic studies may hide multiple small-scale events. This work also reveals that the same slide scarps can be reactivated and generate slides with different flow behaviors.Plain Language Summary When studying large underwater landslides, determining whether what we see in our data was created by one large landslide event or several smaller events is very difficult due to the inaccessibility of the deep sea. But, being able to distinguish between different events and their frequency allows for more accurate risk assessments. Forty years ago, a large landslide was discovered in the northeast Atlantic, on the flank of an underwater plateau offshore of western Ireland. Studies since its discovery have interpreted it as one large event. With present-day technology and a higher resolution data set, we have discovered that it is composed of several landslides. The most recent, but very small and localized event, happened in the last 1,000 years. The one before is happened 10,000 years ago, and it was the size of 680,000 Olympic-size swimming pools. Around 22,000 years ago, a landslide 250 times bigger slid down the slope. Two more similar size events happened more than 200,000 years ago, but the further back in time we go the data resolution gets poorer. We think that the sizes of large underwater landslides found in the world's oceans and lakes may have been significantly overestimated, but their frequency may have actually been underestimated.
“…Further corroborating evidence comes in the form of the sheared section in core CE11_03 that appears as though in situ layers have been locally deformed, possibly due to the lateral pressures emanating from the toe of the slide plowing through the adjacent seafloor. Different scenarios for modeling of Slide C to match the deposits as seen on the bathymetric data reveal that the best fit resulted when a Bigham rheology was adopted with either a velocity-dependent term or with basal frictional properties (Salmanidou et al, 2018).…”
Section: Styles Of Mass Transportmentioning
confidence: 99%
“…Attempts to model the flow behavior of Slides A and B, using the same approach as for slide C, demonstrated that this was not possible and the modeled deposits mapped beyond the actual ones (Salmanidou et al, 2018). This was attributed to potentially different rheological properties (Salmanidou et al, 2018).…”
Section: Styles Of Mass Transportmentioning
confidence: 99%
“…Attempts to model the flow behavior of Slides A and B, using the same approach as for slide C, demonstrated that this was not possible and the modeled deposits mapped beyond the actual ones (Salmanidou et al, 2018). This was attributed to potentially different rheological properties (Salmanidou et al, 2018). Therefore, the assumption that slide events that occur in the same area and as a result should have the same lithological characteristics, and by extension rheological characteristics, is wrong, at least for this case study, as demonstrated by Salmanidou et al (2018) and by the different deposits we find in the cores in this study.…”
One of the most challenging tasks when studying large submarine landslides is determining whether the landslide was initiated as a single large event, a chain of events closely spaced in time or multiple events separated by long periods of time as all have implications in risk assessments. In this study we combine new multichannel seismic profiles and new sediment cores with bathymetric data to test whether the Rockall Bank Slide Complex, offshore western Ireland, is the composite of multiple slope collapse events and, if so, to differentiate them. We conclude that there have been at least three voluminous episodes of slope collapse separated by long periods of slope stability, a fourth, less voluminous event, and possibly a fifth more localized event. The oldest event, Slide A (200 km 3 ), is estimated to be several hundred thousand years old. The second event, Slide B (125 km 3 ), took place at the same location as slide A, reactivating the same scar, nearly 200 ka ago, possibly through retrogression of the scarp. Slide C (400 km 3 ) took place 22 ka ago and occurred further north from the other slides. Slide D was a much smaller event that happened 10 ka ago, while the most recent event, albeit very small scale, took place within the last 1,000 years. This study highlights the need to thoroughly investigate large slide complexes to evaluate event sequencing, as seismic studies may hide multiple small-scale events. This work also reveals that the same slide scarps can be reactivated and generate slides with different flow behaviors.Plain Language Summary When studying large underwater landslides, determining whether what we see in our data was created by one large landslide event or several smaller events is very difficult due to the inaccessibility of the deep sea. But, being able to distinguish between different events and their frequency allows for more accurate risk assessments. Forty years ago, a large landslide was discovered in the northeast Atlantic, on the flank of an underwater plateau offshore of western Ireland. Studies since its discovery have interpreted it as one large event. With present-day technology and a higher resolution data set, we have discovered that it is composed of several landslides. The most recent, but very small and localized event, happened in the last 1,000 years. The one before is happened 10,000 years ago, and it was the size of 680,000 Olympic-size swimming pools. Around 22,000 years ago, a landslide 250 times bigger slid down the slope. Two more similar size events happened more than 200,000 years ago, but the further back in time we go the data resolution gets poorer. We think that the sizes of large underwater landslides found in the world's oceans and lakes may have been significantly overestimated, but their frequency may have actually been underestimated.
“…The tsunami simulations have a duration of 2 h and Δ t =0.1 s. To measure the free surface elevation, we introduce 80 gauges in the domain, almost half of which are located offshore and the rest of them onshore, close to the coastline (figure 3). We concentrate the vast majority of the gauges in the area around Belmullet in Co. Mayo (figure 3 b ), as it is expected to be the first and probably most inundated area by the propagating tsunami waves [45]. Figure 3.( a ) The computational domain (source: EMODnet and GEBCO-08) and the virtual gauges used to measure the free surface elevation.…”
Section: Numerical Simulations and Posterior Distributionsmentioning
Statistical methods constitute a useful approach to understand and quantify the uncertainty that governs complex tsunami mechanisms. Numerical experiments may often have a high computational cost. This forms a limiting factor for performing uncertainty and sensitivity analyses, where numerous simulations are required. Statistical emulators, as surrogates of these simulators, can provide predictions of the physical process in a much faster and computationally inexpensive way. They can form a prominent solution to explore thousands of scenarios that would be otherwise numerically expensive and difficult to achieve. In this work, we build a statistical emulator of the deterministic codes used to simulate submarine sliding and tsunami generation at the Rockall Bank, NE Atlantic Ocean, in two stages. First we calibrate, against observations of the landslide deposits, the parameters used in the landslide simulations. This calibration is performed under a Bayesian framework using Gaussian Process (GP) emulators to approximate the landslide model, and the discrepancy function between model and observations. Distributions of the calibrated input parameters are obtained as a result of the calibration. In a second step, a GP emulator is built to mimic the coupled landslide-tsunami numerical process. The emulator propagates the uncertainties in the distributions of the calibrated input parameters inferred from the first step to the outputs. As a result, a quantification of the uncertainty of the maximum free surface elevation at specified locations is obtained.
“…The vertical component u z (x, t) of the seabed deformation is calculated depending on the physics of tsunami generation, e.g. via co-seismic displacement for finite fault segmentations by Gopinathan et al (2017), submarine sliding by Salmanidou et al (2017Salmanidou et al ( , 2018 etc. The time-dependency in u z (x, t) enables the tsunami to be actively generated (Dutykh and Dias (2009)).…”
Abstract. In this paper, we present the VOLNA-OP2 tsunami model and implementation; a finite volume non-linear shallow water equations (NSWE) solver built on the OP2 domain specific language for unstructured mesh computations. VOLNA-OP2 is unique among tsunami solvers in its support for several high performance computing platforms: CPUs, the Intel Xeon Phi, and GPUs. This is achieved in a way that the scientific code is kept separate from various parallel implementations, enabling easy maintainability. It has already been used in production for several years, here we discuss how it can be integrated into 5 various workflows, such as a statistical emulator. The scalability of the code is demonstrated on three supercomputers, built with classical Xeon CPUs, the Intel Xeon Phi, and NVIDIA P100 GPUs. VOLNA-OP2 shows an ability to deliver productivity to its users, as well as performance and portability on a number of platforms.
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