Seismic Signals: Seismic Wave & Imaging Quiz

As depth increases, the diffraction curves become wider. This is because diffraction occurs when waves encounter an obstacle or pass through a narrow opening. When the waves pass through a larger opening or encounter a larger obstacle, they spread out more, resulting in wider diffraction curves. Therefore, it is true that diffraction curves are wider as depth increases.

The statement is false because Rayleigh waves have a velocity that is slower than P-waves. Rayleigh waves are a type of surface wave that travel along the Earth's surface and cause the ground to move in an elliptical motion. They are slower than P-waves, which are the fastest seismic waves and travel through the interior of the Earth. Therefore, the given statement is incorrect.

Shear waves are a type of seismic waves that travel through solids but cannot pass through liquids. Water is a liquid, so shear waves cannot pass through it. Therefore, the given statement is true.

The statement is true because the term "zero-phase" refers to the alignment of the peaks and troughs of a signal with the reference signal. When the ultimate vibroseis signal is correlated with the reference signal, it means that the two signals are compared and matched. If the correlation is successful, it indicates that the peaks and troughs of the ultimate vibroseis signal are perfectly aligned with the reference signal, resulting in a zero-phase signal. Therefore, the statement is true.

Except for bulk modulus (which is the properties of the rock), wavenumber, frequency and velocity can be calculated from a signal waveform.

Rayleigh waves, also known as ground roll, are a type of surface wave that travels along the surface of the Earth. Unlike body waves, such as P and S waves, Rayleigh waves do not penetrate deep into the Earth's interior. Instead, they propagate along the surface, causing the ground to move in an elliptical motion. Therefore, the statement that Rayleigh waves can penetrate deep into the Earth is false.

The correct answer is P-wave > S-wave > Love wave > Rayleigh wave. This is because P-waves are primary waves that travel fastest through the Earth's interior, followed by S-waves which are slower. Love waves and Rayleigh waves are surface waves that travel slower than both P-waves and S-waves. Therefore, the correct velocity sequence from fastest to slowest is P-wave > S-wave > Love wave > Rayleigh wave.

The statement is true because when a wave front intersects with a diffraction curve, it indicates the positions of both the apparent and true image points. This intersection helps determine the locations where the wave is diffracted and forms an image.

The statement is true because shear modulus is a measure of the material's resistance to shear deformation. It describes how difficult it is to deform a cube of material when a shearing force is applied. A higher shear modulus indicates a stiffer material that is more resistant to deformation, while a lower shear modulus indicates a more easily deformable material. Therefore, the statement accurately describes the concept of shear modulus.

This statement is false. Diffraction can actually image reflector dip from 0 to 90 degrees. Diffraction is a phenomenon where waves bend around obstacles or spread out after passing through a narrow opening. It is commonly used in seismic imaging to analyze subsurface structures. The statement incorrectly limits the range of reflector dip that can be imaged using diffraction.

The explanation for the given correct answer is that the Rayleigh integral is indeed a simplified version of the Kirchhoff integral. It is derived by making certain assumptions, such as considering a spherical wavefront and assuming that the source and observer are far apart. These simplifications allow for easier calculations and analysis of acoustic fields. Therefore, the statement that the Rayleigh integral is a simplification of the Kirchhoff integral is true.

The diffraction hyperbola refers to the pattern of waves spreading out after passing through an obstacle or aperture. As the depth increases, the waves have more space to spread out, resulting in a broader diffraction hyperbola. Therefore, the correct answer is "Broader as depth increases."

A reflection seen on a seismic section can be explained through the diffraction concept because diffraction refers to the bending and spreading of waves around obstacles or through openings. When seismic waves encounter subsurface structures such as faults or boundaries between different rock layers, they can diffract or scatter, causing reflections to be observed on a seismic section. These reflections provide valuable information about the subsurface geology and can be used to map and interpret the Earth's subsurface.

A dynamite or air-gun signal is said to be in minimum phase because it has a fast onset and decays quickly. In minimum phase signals, the energy is concentrated in the initial part of the signal, and the amplitude decreases rapidly over time. This is characteristic of explosive signals like dynamite or air-gun signals, which produce a sudden burst of energy followed by a rapid decrease.

A dispersive media is characterized by its velocity function of frequency. This means that the velocity of waves in the media varies depending on the frequency of the wave. In other words, waves of different frequencies will travel at different speeds through the media. This phenomenon is observed in materials such as water or glass, where waves with higher frequencies (shorter wavelengths) tend to travel faster than waves with lower frequencies (longer wavelengths). This velocity-frequency relationship is a key characteristic of dispersive media.

Surface waves do not attenuate linearly with depth. In fact, they tend to become stronger as they propagate closer to the surface. This is because surface waves are primarily influenced by the properties of the uppermost layers of the Earth's crust, where they are generated. As they travel deeper into the Earth, they may lose some energy due to scattering and other factors, but they do not attenuate in a linear fashion.

Rayleigh waves are a type of surface wave that travel along the surface of a medium, such as the ground. The particle motion of Rayleigh waves is not in the direction of propagation, but rather in an elliptical or circular motion. This means that as the wave travels, the particles move both horizontally and vertically in a rolling motion. Therefore, the correct answer is false.

P-waves, also known as primary waves, are a type of seismic waves that are generated by earthquakes or other seismic events. They are the fastest seismic waves and can travel through both solid and liquid media. Unlike S-waves, which cannot pass through liquids, P-waves can also pass through gaseous media. This is because P-waves are compressional waves that propagate by compressing and expanding the material they pass through, and gases can be compressed and expanded. Therefore, the statement that P-waves can pass through gaseous media is true.

The figure shows a seismic activity, and the seismic events indicated in X are surface waves. Surface waves are seismic waves that travel along the Earth's surface and cause the most damage during an earthquake. They have a slower velocity compared to P-waves and S-waves, and they produce a rolling or swaying motion. Surface waves are responsible for the shaking and destruction of buildings and infrastructure during an earthquake.

The characteristics of Stoneley wave include being found at solid-solid interfaces. Stoneley waves are a type of body wave that can be derived from Rayleigh waves and have a speed close to P-wave velocity. This means that they propagate along the boundary between two solid materials.

Before migration, the apparent seismic data is located at wrong position.

The statement "Diffraction response can be evaluated using Eikonal equation" is incorrect. The Eikonal equation is used to describe the propagation of wavefronts, not specifically for evaluating diffraction response. Diffraction is a phenomenon that occurs when a wave encounters an obstacle or passes through a narrow aperture, causing it to spread out and bend around the edges. Diffraction can be analyzed using various mathematical methods such as the Huygens-Fresnel principle or the Fraunhofer diffraction equation. Therefore, the correct answer is False.

Fourier transform is a mathematical tools to convert time domain signal into frequency domain signal and vice versa.

Angular frequency is not a frequency calculated over a period of time. Instead, it is a measure of how quickly an object or system oscillates or rotates. It is defined as the rate of change of angular displacement with respect to time and is measured in radians per second. Therefore, the given statement is false.

Low frequency signal from broadband acquisition will be useful in developing low frequency model, which will be used in the full waveform inversion.

The principle of superposition states that when two or more waves meet at a point, the resultant displacement at that point is equal to the algebraic sum of the individual displacements. This principle is involved in wave field propagation in a homogeneous media. However, the other options - Rayleigh Integral, Gauss Theorem, and Green's Function - are all mathematical methods or concepts that are used in wave field propagation. Therefore, the correct answer is Principle of Superposition.

The statement "The wave field cannot be reconstructed for measurement at far-field" is the correct statement about Evanescent Wave. This means that the wave field, which represents the distribution of the wave at different points in space, cannot be accurately measured or reconstructed at far-field distances. This is because the evanescent wave decays rapidly as it propagates away from the source, making it difficult to capture and measure its properties accurately.

The statement is false because the reflection coefficient as a function of angle for a plane wave impinging on a plane reflector does not obey Newton's Law. Newton's Law refers to the laws of motion and does not directly apply to the reflection of waves. The reflection coefficient is determined by the properties of the reflecting surface and the angle of incidence, and is not related to Newton's Law.

The Fresnel zone is not a function of the angle of incidence. The Fresnel zone is a region around a line of sight where radio waves can be diffracted and interfere with each other. It is determined by the distance between the transmitter and receiver, and is independent of the angle of incidence. Therefore, the given statement is false.

When seismic waves propagate through a medium, they can experience absorption, which refers to the energy loss of the waves as they travel. This absorption leads to a delay in the phase of the seismic signal. In other words, the arrival time of the seismic signal is delayed due to the energy being absorbed by the medium. This delay in phase can affect the accuracy of seismic data interpretation and analysis.

Geometrical spreading is the most probable factor that influences the shot record in the right figure. Geometrical spreading refers to the phenomenon where seismic waves spread out as they propagate through the subsurface. This spreading causes the amplitude of the waves to decrease with increasing distance from the source. In the right figure, the shot record appears differently due to the effect of geometrical spreading, which causes the amplitudes of the seismic waves to decrease as they travel away from the source.

Huygens' Principle states that every point on a wavefront acts as a source of secondary wavelets, which propagate in all directions. These secondary wavelets have the same amplitude and phase as the primary wavefront. The superposition of these secondary wavefronts creates a new wavefront. Therefore, the statement "Amplitude & phase in secondary wavefront is same as the primary wavefront" is incorrect according to Huygens' Principle.

Wave can be diffracted, therefore answer 1 & 2 is wrong. The wave movement is based on the energy transfer, not the heat transfer.

Seismic data acquisition with a higher fold number leads to a better signal-to-noise ratio. This means that the desired seismic signals are stronger and more distinguishable from the background noise. As a result, the seismic image produced will have clearer and more reliable data, improving the overall quality of the image.

The diffraction response for a homogeneous single velocity media is characterized by the amplitude decaying exponentially from the apex. This means that as the diffraction wave propagates away from the source, its amplitude decreases rapidly. This is a common behavior observed in diffraction phenomena, where the energy of the wave is dispersed over a larger area as it spreads out. The other options mentioned in the question, such as non-hyperbolic response, asymmetrical phase, and frequency attenuation with depth, are not applicable to the diffraction response in this scenario.

Surface wave is a different type of wave, and not produced from P or S-wave

Lower full fold data refers to having fewer seismic traces or data points per unit area. This means that there are fewer measurements to analyze and interpret, which can result in a lower resolution of the seismic data. With lower full fold data, there may be gaps or uncertainties in the seismic image, making it more difficult to accurately identify and locate subsurface features or formations. Therefore, the statement that lower full fold data may affect the resolution of the seismic data is true.

The statement is false because evanescent waves do exist in real seismic data acquisition. Evanescent waves are a type of wave that occurs when a seismic wave encounters a change in medium or a boundary. These waves are characterized by their decay in amplitude as they propagate away from the boundary. In seismic data acquisition, evanescent waves play a crucial role in imaging subsurface structures and can provide valuable information about the geology of an area. Therefore, it is incorrect to say that evanescent waves do not exist in real seismic data acquisition.

In order to derive a ray tracing signal from an acoustic wave equation, a high frequency approximation to the wave equation is used. This approximation allows for simplification of the equation and focuses on the high frequency components of the wave. By neglecting lower frequency components, the ray tracing signal can be obtained, which provides information about the propagation of the wave and its interaction with the medium it travels through.

Only dispersion equation cannot be derived from wave equation. It is derived from NMO equation.