Table of Contents
How is reflection absorption and refraction related to seismic discontinuity?
A seismic refraction or seismic reflection line is a set of seismographs usually lined up along the earth’s surface to record seismic waves generated by an explosion for the purpose of recording reflections and refractions of these waves from velocity discontinuities within the earth.
Why reflection seismic method are relatively more used than refractive techniques?
The second reason is that the seismic reflection method uses high-frequency (20–50 Hz) seismic energy that resolves features as thin as 50–100 m. While dependent on an accurate velocity model for the data processing, seismic reflection has the potential to image the crust with much more resolution than with refraction.
What is the difference between seismic reflection and seismic refraction in the earth?
In this sense, reflection method is a very sophisticated version of the echosounding used in submarines, ships, and radar systems. Whereas, in seismic refraction method, principal portion of the wave-path is along the interface between the two layers and hence approximately horizontal.
What is seismic reflectivity?
Reflection seismology (or seismic reflection) is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth’s subsurface from reflected seismic waves.
Do P waves reflect or refract?
When P waves pass from solid to liquid, then from liquid to solid, there are sudden changes in direction – they are reflected and refracted . Seismic waves are also reflected and refracted as they pass into different rock types.
What is the difference between diffraction and refraction give an example of each?
If we use water waves as an example, waves hitting shallower water at an angle will slow down and change direction slightly. That is refraction. Waves hitting an island will bend and eventually close in on the “shadow” of the island. That is diffraction.
How seismic reflection and refraction show the presence of layers with in earth?
When seismic waves encounter a rock of a different density, it may reflect off of that layer, or bend as it travels across the boundary. By noting these patterns of reflection and refraction, one can determine the presence and depth of layers within Earth. 2.
Can seismic waves be reflected?
A seismic reflection occurs when a wave impinges on a change in rock type (which usually is accompanied by a change in seismic wave speed).
What is seismic wave refraction?
Refraction is (1) the deflection, or bending, of the ray path of a seismic wave caused by its passage from one material to another having different elastic properties. (2) bending of a tsunami wave front owing to variations in the water depth along a coastline. (Image courtesy Charles Ammon, Penn State)
What is the difference between reflectance and reflectivity?
Another way to interpret this is that the reflectance is the fraction of electromagnetic power reflected from a specific sample, while reflectivity is a property of the material itself, which would be measured on a perfect machine if the material filled half of all space.
Why seismic refraction method is used?
The seismic refraction method utilizes the refraction of seismic waves by rock or soil layers to characterize the subsurface geologic conditions and geologic structure.
Why does seismic refraction important?
Seismic refraction is commonly used to map depth to bedrock and is able to look as deep as 40m below grade. Variations in material density and acoustic velocity of the subsurface, together referred to as acoustic impedance, enable the mapping of earth layering, and an interpretation of material type.
Can S waves be reflected?
S waves cannot pass through the liquid outer core, but P waves can. When P waves pass from solid to liquid, then from liquid to solid, there are sudden changes in direction – they are reflected and refracted . Seismic waves are also reflected and refracted as they pass into different rock types.
What are the similarities between reflection and refraction?
Reflection and refraction are both behaviors of waves , such as light and sound waves. When bouncing off of such surfaces, light reflects in the same angle as it hit the surface. Shiny, rough surfaces cause light to reflect in all directions.
What experiments can you do to show reflection and refraction?
Set up a ray box,slit and lens so that a narrow ray of light is produced.
What is the seismic reflection method?
Seismic reflection is a method of exploration geophysics that provides information about the sub-surface structure of the seafloor. The general principle involves sending artificially generated acoustic waves down the water column and into the seafloor, where the different structures and objects within the Earth’s crust reflect this energy back according to their acoustic impedance.
What are examples of reflection and refraction?
– Display different types of objects that reflect and refract. – Instruct students to shine light through the different objects and have them record on their lab sheet whether the light is refracted or reflected. – Students should look at the Swift GH and then look through the optic tube.