Glossary

Title Definition Acceleration The rate of change of the velocity of an object defined as acceleration. Acoustic The branch of physics that deals with the study of mechanical waves in solids, gases, and liquids including topics such as vibration, sound, ultrasound, and infrasound. Amplitude

The maximum distance/displacement moved by a particle/point from its equilibrium position on a vibrating body or wave measured.

Anisotropic The mechanical properties of the material are not the same in different directions at an arbitrary point during its rotation of axes at a point. Attenuation

The loss/reduction of energy of something over the propagation of it in the medium.

Convolution Convolution is a mathematical integral operation on two functions (f and g) that produces a third function (h) to expresses how the shape of one is modified or overlapped or shifted by the other. Critical angle The critical angle is the angle of incidence, for which the angle of refraction is 90°; i.e., It is an incident angle above which the total internal reflection occurs when light enters a denser medium from a comparatively rarer medium. Data The known direct measurements made by the observer from the real world with a specific objective. Discretization By which the computational domain is divided into so-called sub-domains or elements and their intersection points are defined as nodes. Displacement

Displacement is the measurement of a straight path between two positions/objects, irrespective of the path travelled from one position/object to another. It is always a vector quantity.

Distance Distance is the measurement of a path travelled between two positions/objects. It is always scalar quantity. See figure in Displacement definition. Domain In general, the domain refers to the set of all inputs given to a function. In seismics, we parameterize the subsurface to process the inputs signal in either time/frequency forms, and these are characterized as domains in which we do further processes based on mathematical relations. Elasticity The deformations of the body are completely reversible, once the external forces or load is removed from the body. Error Error is defined as the measure of the estimated difference between the calculated value of a function and its true value. Force Force is an external influence that can change the motion of the body or the state of the rest position. It is a vector quantity. Forward problem

The problem by which we can calculate the theoretical response for a particular model from a numerical representation.

Global maxima In Optimization problems, the function exhibits many extrema (minima/maxima) for the range of input, among those, the point at which the function having the largest value is termed as global maxima. See figure in global minima. Global minima

In Optimization problems, the function exhibits many extrema (minima/maxima) for the range of input, among those, the point at which the function having the smallest value is termed as global minima.

Ground roll Ground roll is a type of seismic coherent noise caused by surface waves. It is characterized with high amplitudes and low frequency and low velocity in seismic records. Homogeneous Material property doesn't change during its translation.; i.e., at every point the material properties are invariant. Heterogeneous Material properties will change during their translation; i.e., the material properties vary from point to point. Interpolation Estimation or prediction of new data points from the range of available known data points is referred to as interpolation. Inverse problem

The problem by which we can calculate the model parameter estimates of a particular model, which caused for observations from inverse theory. Note that the role of inverse theory is to provide information about unknown numerical parameters that go into the model, not to provide the model itself.

Isotropic The mechanical properties of the material are the same in all directions at an arbitrary point during its axel rotation at a point. First break/Direct The earliest refracted arrival energy propagated from source to receiver associated with the weathering layer often constitutes a direct/first arrival on seismic shot gather. These are very useful in making statical corrections in the seismic data processing sequence. Frequency The number of repeated events occurring per unit of time is called the frequency. Local Maxima In Optimization problems, the function exhibits many extrema (minima/maxima) for the range of input, among those, the point at which the function having the maximum value is termed as maxima/local maxima. See figure in global minima. Seismic Migration The process to create an accurate image of the subsurface by geometrically re-locating the seismic events in either space or time to the actual location occurred in the subsurface rather than the location that it was recorded at the surface. Local Minima In Optimization problems, the function exhibits many extrema (minima/maxima) for the range of input, among those, the point at which the function having the minimum value is termed as minima/local minima. See figure in global minima. Model The defined relationship between the data and parameters is referred to as the model. It is used for calculating the unknown properties from the known measurements. Multiples The seismic events that undergo more than one reflection through the subsurface is characterized as multiples in seismic records. Seismic Noise The unwanted or un-interpretable components of seismic signal from recorded seismic data are characterized as seismic noise. Numerical method The method/tools used for solving the numerical problems. Some of the examples of popular numerical methods for geophysical applications are finite-difference and finite element methods. Parameter The unknowns that we want to answer in terms of numerical values of the specific properties of the world. Time Period The time taken for one cycle length is called the time period. The unit of time period is second. Quality factor The seismic energy dissipated over the time in various ways. The dissipated energy or attenuation of the energy measured in terms of dimensionless seismic quality factor (Q) stored in one cycle. Ray

It is a perpendicular line drawn on a wavefront at any point in the direction of the wave propagation.

Receiver The instruments used for recording the seismic signal is called the receiver. When used for acquisition in water, it is called the hydrophone, and when it is used for land seismic survey, it is called the geophone. Resolution Resolution measures of how large an object needs to be in order to be seen. It can be measured in two ways: in vertical and horizontal directions. Scalar The physical quantity used for measuring only the magnitude. Ex: Density, mass, time and volume. Seismology It is a branch of geophysics that is used to study the elastic/seismic waves propagated through the earth for imaging the subsurface. Slowness The inverse of the velocity (distance covered by an object in unit time) is defined as the slowness. Source The device that generates the propagated energy to perform the dynamic disturbance through the medium. In seismics, there are different kinds of sources available to generate energy: hammer, explosives, vibrator, Airgun etc. along with the natural source in the form of earthquake. Stacking In seismics, stacking refers to adding seismic traces into a single trace for improving the data quality and reduce...