Energy Ratio Plotter
You will need to have the Java runtime environment (JRE) installed on your computer in order to use this software. As of Java Version 7 Update 51, you will also need to add https://www.crewes.org to the Java Exception Site List. This has been tested in Windows 10 using Microsoft Internet Explorer, Microsoft Edge and Mozilla Firefox.
To start the Energy Ratio Plotter click on the 'Launch' button above.
- To use the plotter, select whether the incident wave is P or S, and whether it originates in the upper or lower level. These choices may be changed at any time.
- Also select which components you wish to have plotted. These may also be changed at any time. Only those for one type of incident wave may be displayed simultaneously.
The Energy Ratio Plotter was created at CREWES in March 2002 by Chuck Ursenbach.
- The plot shows how the energy component ratios change with angle of incidence. To see how they change with properties of each medium, use the six scroll bars in the control panel to change the density and velocities of each layer. These may be fixed to particular values in the text fields, or interactively scanned over a range of values using the slider bars. Only four of these six variables are independent, one for the densities and three for the velocities. Accordingly one can use the drop down menus to select up to four density and velocity ratios as well. The slider bars generate ratios between 0 and 2, but other values can be accessed through the text fields. Note that you are not prevented from selecting properties corresponding to a negative Poisson's ratio.
- The location of critical angles is indicated by vertical lines, which may be annotated with the value of the critical angle, and the relevant velocity conditions.
- The scales may be adjusted using the control panel. Angles may only be adjusted to integer numbers of degrees, and the incident angle must be between 0 and 90.
Comments on the Energy Ratios
The energy ratios show what fraction of an incident wave’s energy is carried away from the interface by various types of waves. Because of energy conservation, the energy ratios for all waves corresponding to one of the three possible incident wave types (P, SV, or SH) sum to unity. The energy ratios do not describe however the partitioning of energy flux parallel to the interface. Thus, after a critical point, the energy ratio of one wave will always drop to zero, even though that wave will continue to have a non-zero Zoeppritz coefficient. This indicates an evanescent wave that travels along the interface, but decays exponentially away from it.
- Aki & Richards, 1980, "Quantitative Seismology", vol. I, sec. 5.2.
- Bortfeld, R., 1961, "Approximations to the reflection and transmission coefficients of plane longitudinal and transverse waves," Geophys. Prosp., 9, 485-502.
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