Forces Of Earthquake

Whilst earthquakes are perhaps the most frequently occurring natural hazard, their impact on people, property and communities varies enormously from one place to another. It is possible to identify a number of factors that cause some places to suffer more than others. Whilst some are large scale and are to do with tectonic location, others are decided at a much more local scale, and relate to building design and levels of preparedness.

The 1906 San Francisco Earthquake tectonic setting was in the outermost shell of earth known as the crust this is composed of rigid plates that have been moving for hundreds of millions of years. Two of these moving plates meet in western California; the boundary between them is a zone of faults, the principal one being the San Andreas fault. The horizontal sliding of the Pacific Plate relative to the North American Plate, causes earthquakes along the San Andreas fault and similar plates near the region. The San Andreas fault is a transform plate boundary, accommodating horizontal relative motions (usgs.gov).

One of the most significant earthquakes to hit the San Fernando Valley in the past was the 1971 San Fernando/ Sylmar earthquake. On February 9, 1971 at about 6 o’clock the cities of San Fernando and Sylmar experienced an earthquake that ruptured along the Sierra Madre Fault Zone (Oakeshott, Gordon B). The epicenter of this earthquake was reported to be in the San Gabriel Valley Mountains above the valley. The citizens of both cities felt tremendous shaking. The magnitude of the earthquake was measured as a 6.6 on the Richter scale and the shaking had the intensity of a level 11 (extreme) on the Modified Mercalli system (U.S. Geological Survey). The shaking of this 6.6 magnitude earthquake lasted about 12 seconds with a very strong ground motion. The source of this faulting was located about five miles to the north of the San Fernando valley. The surface faulting of this earthquake was reported to be seen along the surface of the San Fernando fault zone from a point south of Sylmar, the faulting stretched 6 miles more as far as east to the little Tujunga Canyon, also more surface faulting was reported more east as well. In total the maximum surface rupture was 12 miles and the amount of slip was about 6 feet (U.S. Geological Survey). The type of fault scientist label this earthquake to be was an oblique-slip or also known as a thrust. The depth of this earthquake was 13km (8.1 mi) and the peak acceleration was when it reached the Pacoima dam having the speed of 1.25g (U.S.

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

Earthquakes have been recorded throughout history for thousands of years. Even before seismographs in early times, there are records and accounts of mysterious ground shaking. Earthquakes occur when rocks break along an underground fault (UPSeis, 2007). This, in return, causes vibrations through the earth which causes ground shaking. The magnitude of the shaking varies depending on how great the movement along the fault is; the greater the movement, the bigger the earthquake. Some earthquakes are huge and cause significant damage, while others are small and cause little or no damage what-so-ever. Earthquakes are unpredictable, and can happen at any time. It is uncertain where an earthquake will strike, but there is a greater risk

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,

The four main types of earthquake waves are as follows: primary waves, secondary waves, love waves and Rayleigh waves. Primary waves travel away from where the earthquake occur by compressing and expanding as they propagate in liquids, solids , and gasses. They travel throughout the whole earth longitudinally and are faster than secondary waves . Secondary waves only propagate in solids and do not affect the outer liquid core of the planet causing them to be classified as transverse waves. The next two waves are love waves and Rayleigh waves. Love waves move back and forth in the direction they are traveling while Rayleigh waves also move on the surface but are closer to how waves in the ocean move. Their movement is circular in motion as they move through the Earth but the circular motion is retrograde meaning the waves circle backward as they move forward. These two types of waves are classified as surface waves and they occur when primary waves and secondary waves reach the earth's

Earth is a life giving planet. It is also true that it’s never at rest. It is in a daily course of revolution and rotation, making us experience not only night and day, but also seasons. This planet goes through many changes that brings wonders, but also catastrophes. These forces of nature leave damages and deaths all over the world. One of these cataclysm is earthquakes. What exactly is an earthquake? An earthquake is the ground shaking caused by the sudden movement of one block or rock slipping past another along the faults (Lutgens, Tarbuck). There is a process that causes an earthquake to happen. First it involves the heating, followed by

Earthquakes have been a serious trouble in our lives for as long as people have inhabited the earth. These natural disaster such as earthquakes that happen on the earth have been the cause of many deaths in the past century. What can be done about these violent earthquakes that take place nearly without warning? Predicting an earthquake until now has almost been technologically impossible. However, with improvements in technology, more lives have been saved and much more will. All that remains is to research what happens place before, during, and after an earthquake.

Most earthquake happen inside the lithosphere. Because with more deeper it gets, rocks are more softened, or the viscosity increases. The more viscosity the rock gets, the more it absorbs energy and deform smoothly. Base on this viscosity-elasticity nature of the lithosphere, Gunawardana (2017) assumed that the elastic energy accumulated is proportional to the earthquakes released energy.

There are about 15 tectonic or lithospheric plates on the earth’s surface, which have different size and move relative to one another over the earth’s surface. As a result, the crust around the boundaries of the plates bends or deforms, accumulating strong energy during these processes (Briggs, 2006). When the strain becomes too great to bear by the crust in the future, the crust will snap or slip causing earthquakes. As a type of geophysical hazard, earthquakes are inevitable for mankind living on the Earth, which destroy tremendous buildings, and take human life away. However, influences of earthquakes can be reduced if people take appropriate actions. This report provide an overview of two earthquakes that happened in

Earthquakes are an example of seismic activity created by plate boundaries. They can be caused by the subduction of oceanic crust which is densest at 2.9 g/cm3 under continental crust which weighs 2.7g/m3 at destructive plate boundaries. Earthquakes can also occur along conservative plate boundaries such as that shared by the Pacific and North American plates which move at 5-9 cm/year and 2-3 cm/year respectively causing the 1994 Los Angeles earthquake along the San Andreas fault alongside which lies the San Gregorio and Hayward faults. Earthquakes have different impacts dependent on the location of their foci, the point at which they originate from underground, the presence of land in the surrounding areas, but also the human factors such

Let us take a look at how this earthquake in Haiti occurred. Earthquakes happen on the Earth’s lithosphere, which is the outer layer of the Earth. There are three types of plate boundaries: extensional (divergent), compressional (convergent), and transform (J. Louie et al.). In a transform boundary, which is more relevant to the topic at hand, two massive plates called plate tectonics lock up against each other laterally preventing further movement and eventually building up pressure on themselves. This pressure buildup stores potential energy which ultimately translates into kinetic energy when the rocks can no longer hold onto the amount of pressure that builds up causing the two plates to horizontally move or slide abruptly, which is what we know as an ‘Earthquake’ (Tom Harris et al.). Earthquakes can also happen along fault lines, which are cracks that develop from the movement of the tectonic plates. Similarly, as with the plate tectonics, there are three types of faults: normal faults— up and down slippage of rocks or plates—, reverse faults— when a plate goes under another as a result of pushing against each other— and finally, the strike-slip faults— when two plates slip past each other laterally. They are usually found near the edges of the plates— such as the San Andreas Fault in California which

Earthquakes are one of the most frequent natural phenomena in our world that can happen anywhere and anytime, but some areas experience it more frequently than others. For some people, it can be difficult living near an active area of earthquakes, but it's never too hard to prepare. This would also include my family that was a bit surprised that they would ever experience one since they didn’t think we lived in an area where we could possibly have one. Everyone should learn to be more aware and ready in the event that an earthquake was to happen.

Earthquakes generate different types of waves, each travel at different speeds from the epicenter. New evidence shows new type of shock wave, like a sonic boom. It is this new wave that will create a type of earthquake of such great magnitude that scientists have concluded that there is a 99% chance of major earthquake in Sothern California within next 30 years, with the potential of causing 2,000 deaths, 50,000 deaths, 2 billion dollars’ worth of