Large Water Waves Research Articles

Possible Mechanisms for Tsunami‐Like Surge Deposits Due To the Chicxulub Impact at the K‐Pg Boundary at the Tanis Site, North Dakota

AbstractAt Tanis, a unique bi‐directional sediment package occurs precisely at the Cretaceous‐Paleogene (K‐Pg) boundary, recording the first hours of the Paleogene in uncommonly fine temporal detail. The impact ejecta‐bearing sediment package was rapidly emplaced by two massive, ∼10‐m‐high, potentially impact‐triggered surges, that inundated a steep, deeply incised paleo river valley from the direction of the contemporaneous Western Interior Seaway (WIS). Intermingling of fresh‐ and salt‐water fossils at Tanis, coeval brackish water indicators in the nearby region, and historical tsunami observations, suggest that the WIS paleoshoreline was nearby Tanis at K‐Pg time. The interpreted timing for deposition (including ejecta infall) of ∼1–2‐hr immediately post‐impact precludes a direct tsunami from the Chicxulub impact site, which would have required much more than 10 hr to reach Tanis. Seismic waves from the Mw ∼ 11 Chicxulub earthquake, arriving just minutes post‐impact, might have triggered the surge, for example, via seismic excitation of large water waves in the WIS, as proposed by DePalma et al. (2019, https://doi.org/10.1073/pnas.1817407116). Here, we explore this mechanism via a simple mathematical model of seismic excitation and propagation of a water wave into a shallow river and upstream. Matching the observations implies a relatively long source process time of many minutes, such as generated by Chicxulub crater rebound processes, in order to explain sufficient upriver amplitudes and advective transport. Atmospheric waves due to the expanding Chicxulub ejecta curtain might have provided a smaller, secondary contribution during triggering. Thus, the mechanism(s) for the surges at Tanis are now better‐constrained, yet remain incompletely resolved.

Reduced-order precursors of rare events in unidirectional nonlinear water waves

We consider the problem of short-term prediction of rare, extreme water waves in irregular unidirectional fields, a critical topic for ocean structures and naval operations. One possible mechanism for the occurrence of such rare, unusually intense waves is nonlinear wave focusing. Recent results have demonstrated that random localizations of energy, induced by the linear dispersive mixing of different harmonics, can grow significantly due to modulation instability. Here we show how the interplay between (i) modulation instability properties of localized wave groups and (ii) statistical properties of wave groups that follow a given spectrum defines a critical length scale associated with the formation of extreme events. The energy that is locally concentrated over this length scale acts as the ‘trigger’ of nonlinear focusing for wave groups and the formation of subsequent rare events. We use this property to develop inexpensive, short-term predictors of large water waves, circumventing the need for solving the governing equations. Specifically, we show that by merely tracking the energy of the wave field over the critical length scale allows for the robust, inexpensive prediction of the location of intense waves with a prediction window of 25 wave periods. We demonstrate our results in numerical experiments of unidirectional water wave fields described by the modified nonlinear Schrödinger equation. The presented approach introduces a new paradigm for understanding and predicting intermittent and localized events in dynamical systems characterized by uncertainty and potentially strong nonlinear mechanisms.

Wireless Interactive Sonification of Large Water Waves to Demonstrate the Facilities of a Large-Scale Research Wave Tank

Interactive sonification can provide a platform for demonstration and education as well as for monitoring and investigation. We present a system designed to demonstrate the facilities of the UK's most advanced large-scale research wave tank. The interactive sonification of water waves in the “ocean basin” wave tank at Plymouth University consisted of a number of elements: generation of ocean waves, acquisition and sonification of ocean-wave measurement data, and gesture-controlled pitch and amplitude of sonifications. The generated water waves were linked in real time to sonic features via depth monitors and motion tracking of a floating buoy. Types of water-wave patterns, varying in shape and size, were selected and triggered using wireless motion detectors attached to the demonstrator's arms. The system was implemented on a network of five computers utilizing Max/MSP alongside specialist marine research software, and was demonstrated live in a public performance for the formal opening of the Marine Institute building.

Shallow water waves generated by subaerial solid landslides

SUMMARY Subaerial landslides are common events, which may generate very large water waves. The numerical modelling and simulation of these events are thus of primary interest for forecasting and mitigation of tsunami disasters. In this paper, we aim at describing these extreme events using a simplified shallow water model to derive relevant scaling laws. To cope with the problem,twodifferentnumericalcodesareemployed:one,SPHysics,isbasedonaLagrangian meshless approach to accurately describe the impact stage whereas the other, Gerris, based on a two-phase finite-volume method is used to study the propagation of the wave. To validate Gerris for this very particular problem, two numerical cases of the literature are reproduced: a vertical sinking box and a 2-D wedge sliding down a slope. Then, to get insights into the problem of subaerial landslide-generated tsunamis and to further validate the codes for this case of landslides, a series of experiments is conducted in a water wave tank and successfully compared with the results of both codes. Based on a simplified approach, we derive different scaling laws in excellent agreement with the experiments and numerical simulations.

Characteristics of oceanic impact‐induced large water waves—Re‐evaluation of the tsunami hazard

Abstract— The potential hazard of a meteorite impact in the ocean is controversial with respect to the destructive power of generated large ocean waves (tsunamis). We used numerical modeling of hypervelocity impact to investigate the generation mechanism and the characteristics of the resulting waves up to a distance of 100–150 projectile radii. The wave signal is primarily controlled by the ratio between projectile diameter and water depth, and can be roughly classified into deep‐water and shallow‐water impacts. In the latter, the collapse of the crater rim results in a wave signal similar to solitary waves, which propagate and decay in agreement with shallow‐water wave theory. The much more likely scenario for an asteroid impact on Earth is a relatively small body (much smaller than the water depth) striking the deep sea. In this case, the collapse of the transient crater results in a significantly different and much more complex wave signal that is characterized by strong nonlinear behavior. We found that such waves decay much more rapidly than previously assumed and cannot be treated as long waves. For this reason, the shallow‐water theory is not applicable for the computation of wave propagation, and more complex models (full solution of the Boussinesq equations) are required.

Landslides into reservoirs and their impacts on banks

Mass wasting processes, like slope failures, on the margins of dam reservoirs, lakes, bays and oceans may generate large water waves that can produce disasters due to flooding over the banks, run up along the shoreline and overtopping dam crests. Therefore, the study of slope failures, the subsequent generation of impulse waves and their consequences are of paramount importance for safety. In this paper the generation and propagation of water waves in reservoirs induced by landslides and their impact on banks were investigated by means of a laboratory study carried out at University of Coimbra wave channel, in a flume measuring 12.0 m × 1.5 m × 1.0 m (L × H × W), where two banks with variable slope were placed. The study considered the sliding of calcareous blocks over a sliding slope bank into the reservoir, the generation of impulse waves, their propagation in the reservoir and their impact on the downstream bank. A number of waves were generated by different fallings of calcareous blocks, considering different volumes, sliding slopes, initial positions and reservoir depths. All fallings were recorded by video-camera and the results were processed afterwards to obtain the time history of the falling. The water surface variations due to transient waves were measured at five gauges placed between the banks. The waves overtopping and breaking on the downstream bank were also filmed using a video camera, and the hydrodynamic forces on this bank were also measured using four pressure transducers.

Comparison between Computed and Experimentally Generated Impulse Waves

Large water waves caused by massive slide impacts are a potential hazard along waterways, coastal areas and Alpine regions. Experimental research has been conducted at the Swiss Laboratory of Hydraulics to assess the risk from landslide-generated impulse waves. Analogously, the Centro Elettrotecnico Sperimentale Italiano performed numerical simulations of initial landslide and consequent impulse wave propagation using two mathematical models based on the conservative shallow-water equations. This paper presents the experimental test results and numerical predictions of impulse waves in a flume for a range of stillwater depths, landslide volumes, and impact velocities at laboratory scale. The comparison between the measured and predicted wave free surface profiles generally produced corresponding wave heights, although the initial wave peak is too steep and arrives too early. Excluding spurious random effects, the relative differences between measured and numerically computed maximum wave heights ranged wi...

Long-Period Effects of the Denali Earthquake on Water Bodies in the Puget Lowland: Observations and Modeling

Analysis of strong-motion instrument recordings in Seattle, Washington, resulting from the 2002 M w 7.9 Denali, Alaska, earthquake reveals that amplification in the 0.2- to 1.0-Hz frequency band is largely governed by the shallow sediments both inside and outside the sedimentary basins beneath the Puget Lowland. Sites above the deep sedimentary strata show additional seismic-wave amplification in the 0.04- to 0.2-Hz frequency range. Surface waves generated by the M w 7.9 Denali, Alaska, earthquake of 3 November 2002 produced pronounced water waves across Washington state. The largest water waves coincided with the area of largest seismic-wave amplification underlain by the Seattle basin. In the current work, we present reports that show Lakes Union and Washington, both located on the Seattle basin, are susceptible to large water waves generated by large local earthquakes and teleseisms. A simple model of a water body is adopted to explain the generation of waves in water basins. This model provides reasonable estimates for the water-wave amplitudes in swimming pools during the Denali earthquake but appears to underestimate the waves observed in Lake Union.

Tsunami Run-up—A Hydraulic Perspective

On December 26, 2004, an intense earthquake located in front of the Island of Sumatra generated a massive tsunami that severely impacted the shores of the Indian Ocean, particularly from Indonesia to Sri Lanka. It damaged the coastal infrastructure and caused great loss among the population. The disaster had a twofold origin, namely, an earthquake of intensity 8.9 on the Richter scale and a tsunami that washed away complete reaches of the coast. The wave celerity in the sea was typically 200 m/s and reduced to some 10 m/s on the original shoreline. Fig. 1 a shows the run-up of the tsunami in Khao Lak, Thailand, dwarfing a person trying to run across the sand to safety. There, the maximum recorded wave height amounted to 8.7 m. Fig. 1 b highlights the massive air entrainment in the bore developing along the shore of Phi Phi Island, Thailand. Prior to the December 26 disaster, only specialists knew what a tsunami was: The Japanese word means “harbor wave.” Because tsunamis are essentially shallow-water waves, their development may be recorded at the bottom of the water body, even thousands of meters below the free surface. Even large tsunamis may hardly be detected with satellites because their wave height is limited to some 10 m along with a wave length of more than 100 km. The destructiveness of tsunamis develops during the run-up on shores as the enormous forces originating from the generation process are dissipated. Tsunami run-up is a complicated phenomenon because of the complex nonlinear wave pattern along with the air entrainment and the sediment transport, resulting in a three-phase flow. Natural disasters such as the tsunami described can hardly be human-controlled. However, must the populace face its destiny so helplessly? People living close to a coast should realize that earthquakes normally are accompanied by large water waves, and the spontaneous reaction should be retreating to slightly higher elevations. Further, buildings should be designed and constructed massive enough to withstand both earthquakes and tsunamis. Living in a country without ocean border, these statements may be irrelevant, yet Switzerland faces similar dangers of a different origin. Mega-tsunamis are defined as waves of which the wave height is typically above 100 m. They originate from a huge mass displacement of earth, rock, snow, or glacier into or below a large water body. An impulse wave in an ocean generated by underwater landslides, earthquakes, or asteroid impacts is referred to as a tsunami. The highest observed impulse wave occurred in the

Computer simulations of tsunamis due to sector collapse at Stromboli, Italy

Stromboli is an island volcano of the Aeolian Volcanic Arc, characterised by persistent activity. The cone rises about 2500–3000 m from its submarine base with very steep slopes; its summit at 924 m above the sea level. The subaerial growth of Stromboli, occurred in the last 100 ka, has been marked by repeated episodes of large gravitational collapses especially affecting the NW flank of the island in the last 13 ka. The last one occurred less than 5000 years ago forming the deep depression on the NW seaward flank, named Sciara del Fuoco (SdF), and it produced very likely large water waves. This paper envisages a scenario where a huge mass of volcanic material collapses into the sea in the same sector in which the SdF collapse took place in Holocenic times and it computes possible tsunami evolutions assuming the present-day bathymetry. Numerical simulations are performed by means of two distinct models; one for the mass collapse and one for the tsunami. Slope failure dynamics are calculated with the aid of a Lagrangian model: the landslide is subdivided into blocks, and the motion of each constituent block is calculated by applying the basic principle of mechanical momentum conservation, with block–block and block–ambient interactions being taken into account. Water waves are computed by solving a system of shallow-water equations including a forcing term dependent on the sliding mass motion. The finite-element (FE) technique is employed since it permits the use of non-uniform grids, which are adequate to account for marine basins with irregular coastlines. In addition to the sensitivity analysis concerning the main parameters governing the slide motion, two main cases are explored, differing in the slide path followed by the mass. The resulting tsunami is very large, with giant waves as high as several meters (tens of meters in the worst cases) impinging the coast. Due to the strong wave refraction induced by bathymetry, waves travel around the island, affecting even the island coast opposite the source.

Numerical Simulations of Large Water Waves due to Landslides

A mathematical model based on the hydrodynamic shallow water equations is developed for numerical simulation of slide generated waves in fjords. The equations are solved numerically by a finite difference technique. To examine the performance of the numerical model we have simulated the slide catastrophe in Tafjord, western Norway, 1934. The predicted runup heights are in good agreement with measured runup heights. The effects of wave amplification are estimated in runup zones with gentle beach slopes. The model results reveal wave energy trapping due to the fjord geometry. This causes standing wave oscillations in accordance with the observations.