Seismic Discontinuity

Seismic discontinuities are mainly produced by the seismic waves and there comes an abrupt behavior which is mainly caused due to physical and the chemical properties in that place but the other places surrounding the place are normal and there is no abrupt behavior in those places. A discontinuity is mainly recognized as any type of mechanical break with the big pieces of rocks and it also includes joints, weak Jones, and faults. In geology the word “discontinuity” is used for a surface at which seismic waves change velocity.

Seismic Discontinuity

Advantages of Seismic waves reading

The best way to know different types of Tectonic activity in the crust of the Earth is through Seismic waves and it also helps us to know where the epicenter of the earthquake is located. It also helps us to know how the waves travel and in which direction the waves are traveling. It also gives us knowledge about the interior part of the earth which consists of a series of concentric shells which contain the outer crust, a mantle, an outer core of the liquid, and a solid inner core.

Strongest part of Seismic Discontinuity

The strongest part of the Seismic Discontinuity is seen on the graph which represents velocity vs depth which is known to be situated in a depth of around 2900 km. The part which is just lower to this P-wave velocity is known to be less than 30% and just above it, the S-waves are completely reduced. This is also known as the boundary between the outer part of the core which is known as the outer core and the mantle.

Causes of Seismic Discontinuities

Due to the sudden jump in the seismic in the velocities caused by seismic which takes place around a boundary is known as seismic discontinuities. Seismic stations which are situated within 200 km of a continental earthquake report the time which travels which increases regularly with the distance to the source.

Production of Seismic

The production of seismic takes place by all of a sudden movement in the materials which are within the earth which includes a slip along with a fault which is produced during an earthquake. Seismic waves are also caused by volcanic eruptions, avalanches, landslides, huge explosions, and also sometimes by the rushing rivers. It is mainly an elastic wave that is generated by an impulse and this impulse is created by earthquakes and explosions.

Types of Seismic Waves

There are mainly 4 types of waves which includes P-wave Motion, S-wave Motion, Rayleigh-wave Motion, Love-wave Motion

P-wave Motion: It is known as the primary body wave and also the first seismic wave which can be detected by the seismographs and this motion can perform its movement through both the solid and the liquid rock.

S-wave Motion:  It is also known as the secondary waves which oscillate the ground in a perpendicular direction. The speed of S-waves is 1.7 times slower than P-waves and it produces vertically and horizontally on the ground surface.

Rayleigh-wave Motion:  It is a type of motion in which the movement in the surface is in an elliptical way. This motion produces two components of motion in the direction of propagation i.e. horizontally and vertically.

Love-wave Motion:  It is a type of motion in which the surface waves move parallel to the surface of the earth and perpendicularly to the direction in which they propagate.

Propagation of Seismic waves

The propagation of the seismic waves takes place in more than one way which are known as the wave bodies and the surface waves. The propagation of the body waves mainly takes part in the inner part of the body and it also illuminates the deep geological target. Reflected P, SH, and SV signals can be generated which are needed to characterize the reservoirs and also to evaluate the prospects. The wave field of the seismic waves is a fully elastic seismic wave field that propagates through isotropic earth which consists of a P-wave component and two shear wave components which are the SV and SH.

Calculation of Seismic waves 

The speed of the wave is determined by the properties which are physical in nature Of the material through which the wave will propagate. In the case of a string that is vibrating c2=F/ρ where F is known as the tension force of the string whereas ρ is known as the density. The Seismic wave equation is known as:

“ρu¨ = ∇λ(∇ · u) + ∇µ · [∇u + (∇u) T ] + (λ + 2µ)∇∇ · u − µ∇ × ∇ × u.”

Conclusion

From this article, we came to know the types of seismic waves and also came to know how the seismic waves are produced. The article has also discussed the causes and the strongest part of the seismic wave. We also came to know the propagation of the seismic waves and also have gone through how the Seismic waves are calculated and also came to know that the wave field of the seismic waves is also elastic. This article has also described the four types of seismic waves in detail which has also described the movements of different types of movements.