# Tag Info

## Hot answers tagged waves

26

It is called "antipodal focusing". See for example Antipodal focusing of seismic waves observed with the USArray. We present an analysis of the M-w = 5.3 earthquake that occurred in the Southeast Indian Ridge on 2010 February 11 using USArray data. The epicentre of this event is antipodal to the USArray, providing us with an opportunity to observe in ...

23

Ocean waves (and also in mediterranean type seas and larger lakes, but on a smaller scale) are generated by two processes: locally generated waves ("wind waves"), which follow the direction of the wind; waves generated further out in the sea (i.e. "swell waves"), which do not necessarily follow the direction of the wind. During the night, you are probably ...

22

Tsunamis and sound waves are different types of wave - one is a transverse wave and the other is a longitudinal one. Let's look at the factors that influence the speed of each one. Tsunami - transverse wave in shallow water A transverse wave is one of the type that we think of from day to day - where the direction of oscillation is perpendicular to the ...

21

In water wave physics, when we say that the wave "feels" the bottom, we mean that the water depth affects the properties of the wave. The dispersion relationship for water waves is: $$\omega^2 = gk \tanh{(kd)}$$ where $\omega$ is the wave frequency, $k$ is the wavenumber, $d$ is the mean water depth, and $g$ is gravitational acceleration. We ...

20

There are two important ways to recognize different types of waves in seismic records: Their velocity. These waves travel at different speeds: P-waves are fastest, then S-waves, then Love waves, then Rayleigh. Since seismic recordings are measures of earth displacement, particle velocity, or water pressure over elapsed time, this means the waves show up at ...

17

In simplest terms, it simply means that: if the source signal is shifted by some amount of time Δt, but otherwise unchanged, then the seismogram will also be shifted by Δt, but otherwise unchanged; and the seismogram generated by the sum of two (or more) source signals is the sum of the seismograms that would've been generated by each of the ...

17

To my knowledge, the best study looking at potential explanations for the Red Sea crossing is the one by Nof and Paldor (1992). They present a couple of plausible scenarios for the crossing. The main one is the effect of strong winds blowing along the Gulf of Suez and they find that the sea level drop could be sufficient: It is found that, even for ...

17

Feel the bottom refers to the fact that the wave-induced velocity field extends all the way from the top of the water column to the bottom of the water column. When the wave "feels the bottom" it means that there is some interaction with the bottom boundary. A very thin boundary layer develops at the bottom where vorticity is generated due to the velocity ...

17

The physical process you describe is known as wave shoaling. At the basic level, waves propagating into shallow water become shorter and higher, and consequently, steeper. In shallow water, the water particles near the crest move forward faster than those below them. Similarly, the particles near the trough move backward faster than those above them. This ...

16

P and S waves are fundamentally different, when it comes to properties of the wave. An example might be that P waves can travel through fluids while S waves cannot. However, when it comes down to wave theory, these two are just different polarizations of a mechanical wave. Seismology In seismics this concept may be puzzling as we make some very ...

14

First, inhomogeneities in the ocean are in fact quite common. There are density gradients in both horizontal and vertical directions and those gradients result in the baroclinic circulation of the ocean. The density gradients in the ocean are caused by salinity and temperature differences. Rossby waves are common in the ocean. They propagate along lines of ...

13

Yes. Spectral wave models cannot model storm surge because the wave energy balance equation that they integrate does not describe the physical processes associated with storm surge. Wave models solve the wave energy balance equation: $$\dfrac{\partial E}{\partial t} + \dfrac{\partial (c_gE)}{\partial x} + \dfrac{\partial (\dot{k}E)}{\partial k} + \dfrac{... 12 This is a very good question, not just important to seismic inversion, but also modeling in general. Lets set this problem up differently. Lets say point's A and D are nodes. Each node represents a system of equations, and these equations are only calculated on these points. Therefore, the model can only exist on the points in which they are calculated. ... 12 To add to the excellent answer by aretxabaleta: This is what happens for eastward flow over a step change in depth. Note that the wavy pattern is seen from above, and it veers right due to the step and the conservation of potential vorticity (and the fact it is in the Northern Hemisphere). Similar to a particle displaced from its equilibrium in a buoyancy ... 12 There are few known mechanisms that lead to the generation of Rogue waves, such as the ones you mentioned, but essentially all Rogue waves are the due to the nonlinear wave dispersion characteristics of large groups of waves. I can imagine one approach to predicting the emergence of such waves is to simulate the evolution of initial wave states with Navier-... 12 As SimonW points out strong tidal currents will modify the wave shape and significant height. The Wolf & Prandle (1999) study provides a neat summary description of the effects of currents (of any kind) on waves: (i) Wave generation by wind—the effective wind is that relative to the surface current, and the wave age (cp/U*) and effective surface ... 12 The stability correction factor ASF is related to the effects of atmospheric stability (function of buoyancy and shear) on wave growth, and has been implemented in Wavewatch3 in the Tolman and Chalikov 1996 input source term. The code where the correction happens can be found in w3updtmd.ftn: ! 5. Stability correction ( !/STAB2 ) ! Original settings : !... 10 I think the best option for sediment transport modeling is the Community Sediment Transport Modeling System (CSTMS) package that was developed for ROMS. CSTMS was created by a group of sediment transport modelers lead by the USGS. One of the many benefits is that it is open-source and, thus, free. The model was designed for realistic simulations of processes ... 10 Whitecapping refers to the steepness-induced wave dissipation in deep water during which some air is entrained into the near-surface water, forming an emulsion of water and air bubbles (foam) that appears white. It occurs when the velocity of individual water particles near the wave crest exceed the phase speed of the wave, causing the front face of the wave ... 10 These are rotor clouds, and are manifestations of "Lee Waves", a particular kind of internal "gravity wave" (better defined as "buoyancy effect"). Forced convection helps form these clouds as warm, moist air is forced upward by both wind from behind and the mountain barrier in front. The upward movement forces cooling and condensation of vapor into clouds. ... 9 Yes, wave variance or energy spectrum, direcional or non-directional is positive-definite as @aretxabaleta said in the comment. In linear water-wave theory, the surface elevation is described as a linear superposition of sinusoids:$$ \eta(t) = \sum_{i-1}^{N}a_i \sin(f_i t + \phi_i) $$where a_i, f_i and \phi_i are the amplitude, frequency and ... 9 Two-way time to depth calibration is a vertical problem. How you handle deviated wells probably depends a bit on how you are tying the wells. Here are two things to watch out for: You should be tying to true vertical depth (TVD) anyway — make sure you're not using measured depth somehow. I expect you are using TVD — so the deviated section will be ... 9 The only open and ongoing data source for in-situ ocean wave measurements I am aware of is the National Data Buoy Center. Though NDBC manages data service from plenty of moored buoys in the Gulf of Mexico and the Atlantic and Pacific coasts of North America, unfortunately there isn't much in your region of interest. The only buoys I have found that are ... 8 One thing that I would add is a discussion of a physical parameter that is a simple measure of whether a wave is going to topple or not. The Froude number is defined as the ratio of the maximum absolute fluid velocity, U, and the wavespeed, c: F = U/c Because of the mechanism explained by IRO-bot, In shallow water, the water particles near the ... 8 You can automatically detect the P and S waves for an event but I don't know of a way to automatically extract the Rayleigh and Love waves directly from the seismograms. As @kwinkunks points out things are complicated in the real world. Understanding an event is an iterative bootstrapping process that is best done by looking at recordings from several ... 8 Coastal trapped Kelvin waves are important processes contributing to variability in the sea surface height and temperature near the coast. Field studies have measured large temperature fluctuations mainly made up of low-frequency internal Kelvin waves mostly of semi-diurnal tidal period at the continental shelf on the great barrier reef (Wolanski, 1983). ... 8 In the picture above we see an internal wave propagating in the direction of the wavenumber vector$$\mathbf{K} = k \mathbf{e_x} + m \mathbf{e_z} which (in 2D) is given by the vector sum of its components. $\mathbf{e_x}$ and $\mathbf{e_z}$ are unit vectors in the horizontal and vertical directions, respectively. The continuity condition implies that \$\...

7

Seismic, but... There are lots of ways of estimating wavelets. None of them rely on well logs alone, because they don't contain any information about the wavelet. Some methods are purely statistical, some use the seismic data, and some of them use seismic and well logs. Background I recommend reading what you can about wavelet extraction. Especially these ...

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Large parts of Delft3D - including, I think, the sediment transport module - are available in an open source form. The GUI is not currently open source, but (a) Deltares have been offering licences for this for free for academic use; (b) if they are no longer doing this, it is entirely possible to use the software without the GUI. FVCOM also has a sediment ...

7

To supplement the current and very good answers , we can look at a seismogram: from (http://www.bgs.ac.uk/discoveringGeology/hazards/earthquakes/images/dia_seismogram.jpg) As you can see, we know that P-waves(compressional) will generally arrives before S-waves(shear). Also, in general, S-waves will arrive before the much stronger in response body waves. ...

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