Dyke-arrest scenarios in extensional regimes: Insights from field observations and numerical models, Santorini, Greece

AbstractAn equilibrium dune-erosion model is used every six years to assess the capability of the most seaward dune row on the Dutch Wadden islands to withstand a storm with a 1 in 10,000 probability for a given year. The present-day model is the culmination of numerous laboratory experiments with an initial cross-shore profile based on the central Netherlands coast. Large parts of the dune coast of the Wadden islands have substantially different dune and cross-shore profile characteristics than found along this central coast, related to the presence of tidal channels, ebb-tidal deltas, beach-plains and strong coastal curvature. This complicated coastal setting implies that the predictions of the dune-erosion model are sometimes doubtful; accordingly, a shift towards a process-based dune-erosion model has been proposed. A number of research findings based on recent laboratory and field studies highlight only few of the many challenges that need to be faced in order to develop and test such a model. Observations of turbulence beneath breaking waves indicate the need to include breaking-wave effects in sand transport equations, while current knowledge of infragravity waves, one of the main sand transporting mechanisms during severe storm conditions, is strongly challenged by laboratory and field observations on gently sloping beaches that are so typical of the Wadden islands. We argue that in-situ and remote-sensing field observations, laboratory experiments and numerical models need to be the pillars of Earth Scientific research in the Wadden Sea area to construct a meaningful process-based dune-erosion tool.

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Numerical Simulations of the 2004 Indian Ocean Tsunami Deposits Thicknesses and Emplacements

10.5194/nhess-2018-348 ◽

2018 ◽

Author(s):

◽

Musa Al'ala ◽

Hermann M. Fritz ◽

Mirza Fahmi ◽

Teuku Mudi Hafli

Keyword(s):

Sediment Transport ◽

Indian Ocean ◽

Numerical Simulations ◽

Field Data ◽

Numerical Models ◽

Indian Ocean Tsunami ◽

Tsunami Deposit ◽

Field Observations ◽

Tsunami Deposits ◽

2004 Indian Ocean Tsunami

Abstract. After more than a decade of recurring tsunamis, identification of tsunami deposits, a part of hazard characterization, still remains a challenging task not fully understood. The lack of sufficient monitoring equipment and rare tsunami frequency are among the primary obstacles that limit our fundamental understanding of sediment transport mechanisms during a tsunami. The use of numerical simulations to study tsunami-induced sediment transport was rare in Indonesia until the 2004 Indian Ocean tsunami. This study aims to couple two hydrodynamic numerical models in order to reproduce tsunami-induced sediment deposits, i.e., their locations and thicknesses. Numerical simulations were performed using the Cornell Multi-Grid Coupled Tsunami Model (COMCOT) and Delft3D. This study reconstructed tsunami wave propagation from its source using COMCOT, which was later combined with Delft3D to map the location of the tsunami deposits and calculate their thicknesses. Two Dimensional-Horizontal (2DH) models were used as part of both simulation packages. Lhoong, in the Aceh Besar District, located approximately 60 km southwest of Banda Aceh, was selected as the study area. Field data collected in 2015 and 2016 validated the forward modeling techniques adopted in this study. However, agreements between numerical simulations and field observations were more robust using data collected in 2005, i.e., just months after the tsunami (Jaffe et al., 2006). We conducted pit (trench) tests at select locations to obtain tsunami deposit thickness and grain size distributions. The resulting numerical simulations are useful when estimating the locations and the thicknesses of the tsunami deposits. The agreement between the field data and the numerical simulations is reasonable despite a trend that overestimates the field observations.

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The Skew of Polar Crown X-ray Arcades

International Astronomical Union Colloquium ◽

10.1017/s0252921100048041 ◽

1998 ◽

Vol 167 ◽

pp. 430-433 ◽

Cited By ~ 4

Author(s):

A.H. McAllister ◽

A.J. Hundhausen ◽

D. Mackay ◽

E. Priest

Keyword(s):

Magnetic Field ◽

Differential Rotation ◽

Flux Distribution ◽

Numerical Models ◽

Relative Orientation ◽

Axial Component ◽

Field Observations ◽

X Ray ◽

One To One ◽

The One

AbstractThe one-to-one relationship between the chirality of filament channels and the skew (relative orientation) of the overlying coronal arcades can be coupled with the predictions for the axial component of polar crown filaments based on past magnetic field observations to predict the skew of polar crown arcades in the recent cycle 22. We have surveyed the actual skew as seen in the Yohkoh SXT images over the declining phase of cycle 22 and found a result opposite to that expected. The SXT arcades have been compared with numerical models to show that while some of this result can be explained by flux distribution around switchbacks, other mechanisms such as differential rotation are also needed.

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Calibration of numerical models for small debris flows in Yosemite Valley, California, USA

Natural Hazards and Earth System Science ◽

10.5194/nhess-5-993-2005 ◽

2005 ◽

Vol 5 (6) ◽

pp. 993-1001 ◽

Cited By ~ 48

Author(s):

P. Bertolo ◽

G. F. Wieczorek

Keyword(s):

Debris Flow ◽

Debris Flows ◽

Numerical Models ◽

Slope Instability ◽

The Other ◽

Single Channels ◽

Field Observations ◽

Analysis Model ◽

M Cell ◽

Yosemite Valley

Abstract. This study compares documented debris flow runout distances with numerical simulations in the Yosemite Valley of California, USA, where about 15% of historical events of slope instability can be classified as debris flows and debris slides (Wieczorek and Snyder, 2004). To model debris flows in the Yosemite Valley, we selected six streams with evidence of historical debris flows; three of the debris flow deposits have single channels, and the other three split their pattern in the fan area into two or more channels. From field observations all of the debris flows involved coarse material, with only very small clay content. We applied the one dimensional DAN (Dynamic ANalysis) model (Hungr, 1995) and the two-dimensional FLO-2D model (O'Brien et al., 1993) to predict and compare the runout distance and the velocity of the debris flows observed in the study area. As a first step, we calibrated the parameters for the two softwares through the back analysis of three debris- flows channels using a trial-and-error procedure starting with values suggested in the literature. In the second step we applied the selected values to the other channels, in order to evaluate their predictive capabilities. After parameter calibration using three debris flows we obtained results similar to field observations We also obtained a good agreement between the two models for velocities. Both models are strongly influenced by topography: we used the 30 m cell size DTM available for the study area, that is probably not accurate enough for a highly detailed analysis, but it can be sufficient for a first screening.

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Reactivation of magma pathways: Insights from field observations, geochronology, geomechanical tests and numerical models

Journal of Geophysical Research Solid Earth ◽

10.1029/2020jb021477 ◽

2021 ◽

Author(s):

Samuel T. Thiele ◽

Alexander R. Cruden ◽

Xi Zhang ◽

Steven Micklethwaite ◽

Erin L. Matchan

Keyword(s):

Numerical Models ◽

Field Observations

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Seismic triggering of landslides. Part B: Simulation of dynamic failure processes

Natural Hazards and Earth System Science ◽

10.5194/nhess-3-663-2003 ◽

2003 ◽

Vol 3 (6) ◽

pp. 663-682 ◽

Cited By ~ 15

Author(s):

H.-B. Havenith ◽

A. Strom ◽

F. Calvetti ◽

D. Jongmans

Keyword(s):

Numerical Models ◽

Dynamic Effect ◽

Slope Instability ◽

Deformation Mechanisms ◽

Discrete Element Modelling ◽

Diffraction Reflection ◽

Field Observations ◽

Landslide Occurrence ◽

Geological Conditions ◽

Seismic Triggering

Abstract. From field observations it is possible to establish correlations between geological conditions and landslide occurrence. However, in general, it is difficult to assess the affect of individual factors on slope instability because of their mutual interaction. In addition, the dynamic effect of propagating seismic waves significantly increases the complexity of the slope stability problem. Wave diffraction, reflection and focusing effects are dependent on local geological conditions and make it difficult to analyse dynamic sliding mechanisms using field observations alone. As a consequence, in order to examine the influence of various geological and seismic factors on slope movements, it is often necessary to produce numerical models. This paper describes the results of such models as applied to two case studies in Kyrgyzstan: the Ananevo rockslide, located in granite, and the Suusamyr debris slump-flow, situated within soft sediments (see Part A: Havenith et al., 2003). Discrete element modelling (UDEC), adapted both to the discontinuous character of fractured rock and to the heterogeneity of layered mediums, was used. This permitted simulation of deformation mechanisms, including seismically induced bending, block tilting, and slip. Particular attention was paid to the interaction between deformation mechanisms, site-specific amplification effects, and subsurface structure.

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Forecasting the propagation paths of fluid-driven fractures, particularly dikes and inclined sheets

10.5194/egusphere-egu2020-20010 ◽

2020 ◽

Author(s):

Agust Gudmundsson ◽

Kyriaki Drymoni ◽

Mohsen Bazargan ◽

Kayode Adeoye-Akinde

Keyword(s):

Numerical Models ◽

Volcanic Eruptions ◽

Pyroclastic Flows ◽

Propagation Path ◽

Normal Faults ◽

Hydraulic Fractures ◽

Pure Mode ◽

Field Observations ◽

Least Action ◽

Propagation Paths

It is of great importance in many fields to be able to forecast the likely propagation paths of fluid-driven factures. These include mineral veins, human-made hydraulic fractures, and dikes/inclined sheets. The physical principles that control the propagation of all fluid-driven fractures are the same. Here the focus is on dikes and inclined sheets where the selected path determines whether, where, and when a particular dike/sheet reaches the surface to erupt. Here we provide analytical and numerical models on dike/sheet paths in crustal segments (including volcanoes) that include layers of various types (lava flows, pyroclastic flows, tuff layers, soil layers, etc) as well as mechanically weak contacts and faults. The modelling results are then compared with, and tested on, actual data of two types. (a) Seismic data on the paths of dikes/sheets as well as human-made hydraulic fractures, and (b) field data on the actual propagation paths of dikes/sheets in layered and faulted rocksThe numerical results show that, particularly in stratovolcanoes, the paths are likely to be complex with common deflections along layer contacts, in agreement with field observations. &#160;Also, some dikes/sheets may use existing faults as parts of their paths, primarily steeply dipping and recently active normal faults. The propagation path is thus not entirely in pure mode I but rather partly in a mixed mode. The energy required to propagate the dike/sheet is mainly the surface energy needed to rupture the rock, to form two new surfaces and move them apart as the fracture propagates. The energy available to drive the fracture is the stored elastic energy in the hosting crustal segment.From its point of initiation in the magma-chamber roof, a dike/sheet can, theoretically, select any one of an infinite number of paths to follow to its point of arrest or eruption. It is shown that the eventual path selected is the one of least action, that is, the path along which the time integral of the difference between the kinetic and potential energies is an extremum (normally a minimum) relative to all other possible paths with the same endpoints. If the kinetic energy is omitted, and there are no constraints, then least action becomes the minimum potential energy, which was postulated as a basis for understanding dike propagation by Gudmundsson (1986). Here it is shown how this theoretical framework can help us make reliable forecasts of dike/sheet paths and associated volcanic eruptions.Gudmundsson, A., 1986. Formation of dykes, feeder-dykes, and the intrusion of dykes from magma chambers. Bulletin of Volcanology, 47, 537-550.Gudmundsson, A., 2020. Volcanotectonics: Understanding the Structure, Deformation, and Dynamics of Volcanoes. Cambridge University Press, Cambridge.Drymoni, K., Browning, J. Gudmundsson, A., 2020. Dyke-arrest scenarios in extensional regimes: insights from field observations and numerical models, Santorini, Greece. Journal of Volcanology and Geothermal Research (in press).&#160;

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RESONANT OSCILLATIONS IN SMALL CRAFT HARBOURS: OBSERVATIONS AND MITIGATION MODELING EXAMPLES FROM ATLANTIC CANADA

Coastal Engineering Proceedings ◽

10.9753/icce.v36.papers.62 ◽

2018 ◽

pp. 62

Author(s):

Vincent Leys ◽

Victoria Fernandez ◽

Danker Kolijn

Keyword(s):

Case Studies ◽

Analytical Methods ◽

Numerical Models ◽

Long Waves ◽

Field Observations ◽

Existing Structures ◽

Wave Forcing ◽

Infrastructure Design ◽

Small Craft ◽

External Wave

Agitation from swells and long waves can pose serious challenges for harbours, in terms of both infrastructure design and operations. Wave gauge observations from Atlantic Canadian harbours of varying sizes were used to assess how combinations of basin dimensions and external wave forcing may lead to swell agitation, resonance, and scour problems. This paper summarizes how basin resonances were investigated with field observations, analytical methods, and then phase-resolving numerical models. The case studies illustrate how resonance mitigation may require substantial (and sometimes impractical) changes in harbour layout. Swell and scour mitigation may be more readily achieved by modifications or additions to existing structures.

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