Hey everyone, my names Samreen and today I’ll be informing you guys all about Seismic waves in relation to Earthquakes. In other words, we’ll be looking at Seismology, which is the study of the passage of elastic waves through the Earth.
Seismic waves are waves of energy caused by the sudden breaking of rock within the earth or an explosion; these waves are the energy that is transmitted through the earth which is recorded on seismographs, which measures, amplifies, and records the motion of the ground (Endsley, 2016). Many different processes generate seismic waves, including earthquakes.
An Earthquake occurs when there is a sudden movement of the Earth’s crust resulting from the building up of stored energy between two stuck lithospheric
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The linear relationship between applied stress (σ) and resulting strain (∈) is: σ=E∈ Where, E equals the constant of proportionality called an elastic modulus
The original volume (VO) change to final volume (VF) when compared to the pressure change is called bulk modulus (K); which is the measure of the incompressibility of the material.
K=V_O (P-P_O )/(V_O-V_F)
When deforming a solid state by simple shear, a shear strain (Y) is induced by applying a shear stress (σ).
The ratio of these quantities is the rigidity modulus (G):
G=σ/Y
The units of elastic modulus are the same as pressure, MPa (Mega Pascal) or GPa (Giga Pascal).
The bulk modulus (K) and the rigidity modulus (G) are always positive, which means that the velocity of p-waves is always greater than s-waves. S-waves cannot propagate through a liquid medium, this theory is proven when G = 0 is substituted for liquids; the velocity of the wave equals zero (Ucl.ac.uk, 2016).
There are two different types of seismic waves produced during an earthquake; body waves and surface waves.
Body waves travel through the earth’s inner layers. They are reflected and transmitted at interfaces where seismic velocity and/or density change, and they obey Snell’s law (Physicsclassroom.com, 2016), which states that: the ratio of the sines of the angles of incidence and refraction of a wave are constant when it passes through two given media. P-waves and
In Valdivia, Chile 1960 an earthquake changed the lives of many. An earthquake is the violent shaking of the ground that will destroy homes, buildings, landforms, historical monuments, and lives. Earthquakes begin with the breakage of rock along a fault line. When two tectonic plates rub against each other they create an earthquake. Earthquakes will ride along a fault line which will determine how long the quake will go on. The larger and longer the fault like the bigger the earthquake. Earthquakes send out waves, primary waves or, p waves and secondary waves or, s waves travel along the interior of the earth. These two waves are called body waves. While detecting the waves, the primary waves appear first then the secondary waves. Primary waves travel through solids, liquids, and gasses, which means they are about to travel through the liquid center. Secondary waves are only able to travel through solids which are why scientists have found that there is a loss of these waves once they reach the center.
Earthquakes can be created on any of the plate boundaries. Earthquakes occur when tension is released from inside the crust. Plates do not always move smoothly alongside each other and sometimes get stuck. When this happens pressure builds up. When this pressure is eventually released, an earthquake tends to occur. The point inside the crust where the pressure is released is called the focus. The point on the Earth's surface above the focus is called the epicentre. Earthquake energy is released in seismic waves. These waves spread out from the focus. The waves are felt most strongly at the epicentre, becoming less strong as they travel further away. The most severe damage caused by an earthquake will happen close to the epicentre.
In longitudinal waves the object doesn’t exactly follow the waves fully instead the object moves in a back and forth motion while the waves continues to move forward through the object. While in transverse waves the object doesn’t follow the waves as well and just moves up and down in the same position.
D. P-wave amplitude is larger than all the other seismic waves recorded on a seismogram.
water fractures within the earth. Causing certain areas of the land to have an earthquake effect
Imagine yourself home doing a couple of sets of jumping jacks but then you feel weary so you stop for a water break. You notice that you kept on bouncing but it wasn’t your body moving it was the Earth that was shaking you, an earthquake occured. Earthquakes happen when the underground continental plates move. Earthquakes can affect the Earth, people, and property. To begin with, when an earthquake happens something on Earth is most likely to change.
Earthquakes are caused when two blocks of earth suddenly slip past one another. The surface where the two blocks slip is called the fault. The earthquake starts below the earth’s surface at the hypocenter, and the location above the hypocenter is called the epicenter. Earthquakes can have foreshocks which is a smaller earthquake that happens before the larger quake. Earthquake can also
Since these earthquakes are caused by tectonic plate movement therefore displacing the ocean floor they are almost always accompanied by massive ocean waves, sometimes reaching heights of over 100 ft and reaching speeds of 500 mph, known as seismic sea waves or more commonly known as Tsunamis4. Alongside the catastrophic events that megathrust earthquakes ensue on an affected region these colossal Tsunami waves further destruct costal lines in their path, sometimes reaching many miles inland.
The energy coming from this rupture is called seismic waves. These waves fan out in every direction from the earthquakes epicenter and results in intense shaking. Once this shaking reaches the earth’s surface, everything from the ground up will also proceed to shake (Wald 2012). In order to measure the size of an earthquake, scientists use seismographs. Seismographs consist of a base, a spring, pen, rotating drum, and a heavy weight. The base is placed in the ground while the weight hangs above. When an earthquake occurs the spring absorbs the shaking and the weight and pen, which remain motionless, record the difference between the shaking and motionless part of the seismograph. Seismograph recordings consist of short and long wavy lines, with long lines indicating a larger earthquake (Wald 2012). These recordings are then
An earthquake would be classified as a sudden ferocious shaking of the ground, typically causing great obliteration because of manoeuvre within the earth’s crust or volcanic action.
The most common cause of earthquakes is movement along faults. Earth’s crust is divided into tectonic plates, which grind past each other at fault boundaries. As tectonic plates move,
Earthquakes are sudden trembling or shaking vibrations. Earthquakes are large spinning spiral winds, that comes together by rocks underground breaks along the fault. There are two types of earthquakes, there is the body waves and the surface waves. Body waves travel at 7/8 km. The body wave is the fastest of the two waves. The surface waves act as a gravity waves that are between two fluids with different density. Unlike hurricanes,
Earthquakes are caused when rock at an underground fault breaks. This release of energy causes seismic waves (Endsley). There are P waves, S waves, and surface waves (Hogan). This is the main cause of earthquakes, though there has been a few, rare occurrences
This can be represented as : v2 = (elastic property / inertial property). Where the elastic property is usually the bulk modulus or Young's modulus of the medium, and the inertial property is the density of the medium.
An Earthquake is the shaking of the earth's surface caused by rapid movement of the earth's rocky outer layer. The sudden shaking of the ground that occurs when masses of rock change position below the Earth's surface is called an earthquake. The shifting masses send out shock waves that may be powerful enough to alter the surface of the Earth, thrusting up cliffs and opening great cracks in the ground.