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Journal articleMiljković K, Collins GS, Bland PA, 2014,
Reply to comment on: “Supportive comment on: “Morphology and population of binary asteroid impact craters”, by K. Miljković, G.S. Collins, S. Mannick and P.A. Bland – An updated assessment”
, Earth and Planetary Science Letters, Vol: 405, Pages: 285-286, ISSN: 0012-821XIn Miljković et al. (2013) we resolved the apparent contradiction that while 15% of the Near Earth Asteroid (impactor) population are binaries, only 2–4% of craters formed on Earth and Mars (target planet) are doublet craters. Using 3D hydrocode simulations to explore the physics of binary impacts, we showed that only 2% of binary asteroid impacts produced well-separated doublets, while the rest covered morphologies ranging from overlapping to elliptical or even circular. We then generated a complete classification dataset to aid in the identification of the (sometimes subtle) morphological characteristics consistent with a binary asteroid impact. We thank Schmieder et al. (2013) for providing additional detailed geochronological constraints which indicate that our lower bound of 2% doublet craters on Earth may in fact be ≤1.5%.
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Journal articleHill J, Collins GS, Avdis A, et al., 2014,
How does multiscale modelling and inclusion of realistic palaeobathymetry affect numerical simulation of the Storegga Slide tsunami?
, Ocean Modelling, Vol: 83, Pages: 11-25, ISSN: 1463-5003The ∼8.15 ka Storegga submarine slide was a large (∼3000 km3), tsunamigenic slide off the coast of Norway. The resulting tsunami had run-up heights of around 10–20 m on the Norwegian coast, over 12 m in Shetland, 3–6 m on the Scottish mainland coast and reached as far as Greenland. Accurate numerical simulations of Storegga require high spatial resolution near the coasts, particularly near tsunami run-up observations, and also in the slide region. However, as the computational domain must span the whole of the Norwegian-Greenland sea, employing uniformly high spatial resolution is computationally prohibitive. To overcome this problem, we present a multiscale numerical model of the Storegga slide-generated tsunami where spatial resolution varies from 500 m to 50 km across the entire Norwegian-Greenland sea domain to optimally resolve the slide region, important coastlines and bathymetric changes. We compare results from our multiscale model to previous results using constant-resolution models and show that accounting for changes in bathymetry since 8.15 ka, neglected in previous numerical studies of the Storegga slide-tsunami, improves the agreement between the model and inferred run-up heights in specific locations, especially in the Shetlands, where maximum run-up height increased from 8 m (modern bathymetry) to 13 m (palaeobathymetry). By tracking the Storegga tsunami as far south as the southern North sea, we also found that wave heights were high enough to inundate Doggerland, an island in the southern North Sea prior to sea level rise over the last 8 ka.
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Journal articleKontoe S, Avgerinos V, Potts DM, 2014,
Numerical validation of four analytical solutions and their use for equivalent-linear seismic analysis of circular tunnels
, Soil Dynamics and Earthquake Engineering, Vol: 66, Pages: 206-219The first part of this paper presents an extensive validation of four analytical solutions for the seismic design of circular tunnels. The validation is performed with a quasi-static Finite Element (FE) model which conforms to the assumptions of the analytical solutions. Analyses are performed for a wide range of flexibility ratios, slippage conditions at soil-lining interface, assuming both drained and undrained behaviour. Based on the numerical predictions the relative merits of the considered analytical solutions are discussed and recommendations are given for their use in design. The second part of this paper explores the use of equivalent linear soil properties in analytical solutions as an approximate way of simulating nonlinearity. The results of equivalent linear site response analyses are used as an input for the analytical solutions. The comparison of the analytical predictions with nonlinear numerical analysis results is very satisfactory. The results of this study suggest that analytical solutions can be used for preliminary design using equivalent linear properties and the corresponding compatible strain as an approximate way of accounting for nonlinear soil response.
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SoftwarePiggott MD, 2014,
Fluidity
Fluidity is an open source, general purpose, multi-phase computational fluid dynamics code capable of numerically solving the Navier-Stokes equation and accompanying field equations on arbitrary unstructured finite element meshes in one, two and three dimensions.It is used in a number of different scientific areas including geophysical fluid dynamics, computational fluid dynamics, ocean modelling and mantle convection. It uses a finite element/control volume method which allows arbitrary movement of the mesh with time dependent problems, allowing mesh resolution to increase or decrease locally according to the current simulated state. It has a wide range of element choices including mixed formulations.Fluidity is parallelised using MPI and is capable of scaling to many thousands of processors. Other innovative and novel features are a user-friendly GUI and a python interface which can be used to calculate diagnostic fields, set prescribed fields or set user-defined boundary conditions.
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Journal articleJacobs CT, Avdis A, Gorman GJ, et al., 2014,
PyRDM: A Python-based Library for Automating the Management and Online Publication of Scientific Software and Data
, Journal of Open Research Software, Vol: 2, ISSN: 2049-9647 -
Journal articleMannie AS, Jackson CA-L, Hampson GJ, 2014,
Shallow-marine reservoir development in extensional diapir-collapse minibasins: An integrated subsurface case study from the Upper Jurassic of the Cod terrace, Norwegian North Sea
, AAPG BULLETIN, Vol: 98, Pages: 2019-2055, ISSN: 0149-1423- Author Web Link
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- Citations: 12
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Journal articleRotevatn A, Jackson CA, 2014,
3D structure and evolution of folds during normal fault dip linkage
, Journal of the Geological Society, Vol: 171, Pages: 821-829Understanding the 3D geometry and evolution of extension-related folds is important because they may document the geometry and evolution of the associated faults, influence sediment routing and accommodation development, and may represent targets for hydrocarbon exploration or CO2 storage. Previous work on extension-related folds has largely been restricted to a 2D plane of observation; in this study we use 3D seismic reflection data from the Gulf of Suez, Egypt to determine the 3D geometry and evolution of fault-parallel folds during dip linkage of a vertically segmented extensional fault array that is locally decoupled across a salt-bearing interval. The 3D geometry of individual faults in the array and adjacent hanging-wall folds varies along strike; rollover structures occur above listric faults, whereas fault-bend folds occur above faults that have a ramp–flat–ramp geometry. Quantitative analysis of fault–fold attributes (e.g. fold amplitude) and the growth history of the fault array indicate that fault shape is controlled by the style of dip linkage, which in turn is controlled by the lateral separation of sub- and supra-salt segments prior to linkage. Small lateral separation yields a relatively subtle change in the overall convexity of the listric fault, whereas larger lateral separation results in a ramp–flat–ramp fault geometry, with the layer-parallel detachment lying within the salt. This study provides a link between fault spacing, style of dip linkage, final fault shape and, ultimately, the style of hanging-wall folding in mechanically layered stratigraphy. Our study indicates that 3D seismic reflection data have the ability to provide us with new 3D insights into the variability of, and controls on, the geometry and evolution of fault-related folds.
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Conference paperGhail RC, Skipper J, Mason PJ, 2014,
Identification of Ground Engineering Hazards in London Through the Use of Predictive 4D Geomodelling Tools
, Switzerland, Engineering Geology for Society and Territory, Publisher: Springer International Publishing, Pages: 907-911Unexpected ground conditions are responsible for a number of engineering problems and hazards across London. A major reason for the unexpected nature of these events is the historical proprietary approach to site investigation, which has restricted knowledge transfer and inhibited the development of a London-wide geological context. Recent changes mean that much of these data are now accessible in the public domain for site investigation and useful in predicting the engineering hazards resulting from complex and variable geology. We advocate applying predictive 4D modelling to better constrain geological structures, facies, fissures and groundwater flow, and adopting an iterative approach that both informs local site models and updates the regional context. Reverse normal faulting, indicative of basin inversion, pull-apart structures and periglacial scour/pingo features are identified in a pilot study regional model. Applying this model to a small site investigation predicted otherwise unexpected faulting, generating horizontal fissuring that causes water to flow along the length of the fault system. Widely adopting this approach in London and other urban areas may substantially reduce the risk of unexpected ground hazards.
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Journal articleITOI T, STAFFORD PJ, KANEKO M, et al., 2014,
21146 Stochastic Ground Motion Simulation for Probabilistic Seismic Risk Assessment
, Summaries of technical papers of annual meeting, Vol: 2014, Pages: 291-292, ISSN: 1883-9363 -
Journal articleParkinson SD, Hill J, Piggott MD, et al., 2014,
Direct numerical simulations of particle-laden density currents with adaptive, discontinuous finite elements
, GEOSCIENTIFIC MODEL DEVELOPMENT, Vol: 7, Pages: 1945-1960, ISSN: 1991-959X -
Journal articleWu M-C, Liu J, Cosgrove J, et al., 2014,
Modelling of Yingxiu-Seichuan fault zone based on refined DInSAR data of 2008 Wenchuan earthquake
, TECTONOPHYSICS, Vol: 630, Pages: 193-207, ISSN: 0040-1951- Author Web Link
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- Citations: 5
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Conference paperCamara A, Nguyen K, Ruiz-Teran AM, et al., 2014,
Comfort in Slender Bridges Subjected to Traffic Loading and Hammering Effects
, 37th International IABSE Symposium -
Journal articleBierman PR, Coppersmith R, Hanson K, et al., 2014,
A cosmogenic view of erosion, relief generation, and the age of faulting in southern Africa
, GSA Today, Vol: 24, Pages: 4-11, ISSN: 1052-5173Southernmost Africa, with extensive upland geomorphic surfaces, deep canyons, and numerous faults, has long interested geoscientists. A paucity of dates and low rates of background seismicity make it challenging to quantify the pace of landscape change and determine the likelihood and timing of fault movement that could raise and lower parts of the landscape and create associated geohazards. To infer regional rates of denudation, we measured10Be in river sediment samples and found that south-central South Africa is eroding ∼5 m m.y.-1, a slow erosion rate consistent with those measured in other non-tectonically active areas, including much of southern Africa. To estimate the rate at which extensive, fossil, upland, silcrete-mantled pediment surfaces erode, we measured10Be and26Al in exposed quartzite samples. Undeformed upland surfaces are little changed since the Pliocene; some have minimum exposure ages exceeding 2.5 m.y. (median, 1.3 m.y.) and maximum erosion rates of <0.2 m m.y.-1(median, 0.34 m m.y.-1), consistent with no Quaternary movement on faults that displace the underlying quartzite but not the silcrete cover. We directly dated a recent displacement event on the only recognized Quaternary-active fault in South Africa, a fault that displaces both silcrete and the underlying quartzite. The concentrations of10Be in exposed fault scarp samples are consistent with a 1.5 m displacement occurring ca. 25 ka. Samples from this offset upland surface have lower minimum limiting exposure ages and higher maximum erosion rates than those from undeformed pediment surfaces, consistent with Pleistocene earthquakes and deformation reducing overall landscape stability proximal to the fault zone. Rates of landscape change on the extensive, stable, silcretized, upland pediment surfaces are an order of magnitude lower than basin-average erosion rates. As isostatic response to regional denudation uplifts the entire landscape at several meters per million years, valleys
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Conference paperMilbury C, Johnson BC, Melosh HJ, et al., 2014,
THE EFFECT OF POROSITY AND DILATANCY ON THE GRAVITY SIGNATURE OF CRATERS ON THE MOON.
, 77th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A283-A283, ISSN: 1086-9379 -
Journal articleReeve MT, Bell RE, Jackson CA-L, 2014,
Origin and significance of intra-basement seismic reflections offshore western Norway (vol 171, pg 1, 2014)
, JOURNAL OF THE GEOLOGICAL SOCIETY, Vol: 171, Pages: 737-737, ISSN: 0016-7649 -
Journal articleLeinov E, Jackson MD, 2014,
Experimental measurements of the SP response to concentration and temperature gradients in sandstones with application to subsurface geophysical monitoring
, JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Vol: 119, Pages: 6855-6876, ISSN: 2169-9313- Author Web Link
- Open Access Link
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- Citations: 22
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Journal articleJacobs CT, Piggott MD, 2014,
Firedrake-Fluids v0.1: numerical modelling of shallow water flows using a performance-portable automated solution framework
, Geoscientific Model Development Discussions, Vol: 7, Pages: 5699-5738, ISSN: 1991-9611 -
Journal articleMolkenthin C, Scherbaum F, Griewank A, et al., 2014,
A Study of the Sensitivity of Response Spectral Amplitudes on Seismological Parameters Using Algorithmic Differentiation
, Bulletin of the Seismological Society of America, Vol: 104, Pages: 2240-2252, ISSN: 0037-1106Response spectra are of fundamental importance in earthquake engineeringand represent a standard measure in seismic design for the assessment of structuralperformance. However, unlike Fourier spectral amplitudes, the relationship of responsespectral amplitudes to seismological source, path, and site characteristics is notimmediately obvious and might even be considered counterintuitive for high oscillatorfrequencies. The understanding of this relationship is nevertheless important forseismic-hazard analysis. The purpose of the present study is to comprehensively characterizethe variation of response spectral amplitudes due to perturbations of the causativeseismological parameters. This is done by calculating the absolute parametersensitivities (sensitivity coefficients) defined as the partial derivatives of the modeloutput with respect to its input parameters. To derive sensitivities, we apply algorithmicdifferentiation (AD). This powerful approach is extensively used for sensitivity analysisof complex models in meteorology or aerodynamics. To the best of our knowledge, ADhas not been explored yet in the seismic-hazard context. Within the present study, ADwas successfully implemented for a proven and extensively applied simulation programfor response spectra (Stochastic Method SIMulation [SMSIM]) using the TAPENADEAD tool. We assess the effects and importance of input parameter perturbations on theshape of response spectra for different regional stochastic models in a quantitative way.Additionally, we perform sensitivity analysis regarding adjustment issues of groundmotionprediction equations.
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Journal articleGreve S, Paulssen H, Goes S, et al., 2014,
Shear-velocity structure of the Tyrrhenian Sea: Tectonics, volcanism and mantle (de)hydration of a back-arc basin
, EARTH AND PLANETARY SCIENCE LETTERS, Vol: 400, Pages: 45-53, ISSN: 0012-821X- Author Web Link
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- Citations: 17
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Journal articleWinsor K, Carlson AE, Rood DH, 2014,
<sup>10</sup>Be dating of the Narsarsuaq moraine in southernmost Greenland: Evidence for a late-Holocene ice advance exceeding the Little Ice Age maximum
, Quaternary Science Reviews, Vol: 98, Pages: 135-143, ISSN: 0277-3791In southernmost Greenland near Narsarsuaq, the terminal Narsarsuaq moraine was deposited well outside of a historical Little Ice Age (LIA) moraine adjacent to the modern ice margin. Using 10Be surface exposure dating, we determine Narsarsuaq moraine abandonment at 1.51±0.11ka. A second set of 10Be ages from a more ice-proximal position shows that ice has been within or at its historical (i.e., LIA) extent since 1.34±0.15ka. Notably, Narsarsuaq moraine abandonment was coincident with climate amelioration in southern Greenland. Southern Greenland warming at ~1.5ka was also concurrent with the end of the Roman Warm Period as climate along the northern North Atlantic sector of Europe cooled into the Dark Ages. The warming of southern Greenland and retreat of ice from the Narsarsuaq moraine is consistent with studies suggesting possible anti-phase centennial-scale climate variability between northwestern Europe and southern Greenland. Other southernmost Greenland ice-margin records do not preclude a pre-LIA ice-margin maximum, potentially concurrent with a Narsarsuaq advance prior to ~1.51ka, but also lack sufficient ice-margin control to confirm such a correlation. We conclude that there is a clear need to further determine whether a late-Holocene pre-LIA maximum was a local phenomenon or a regional southern Greenland ice maximum, and if this advance and retreat reflects a regional fluctuation in climate. © 2014.
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