The term earthquake comes from the Greek term for “shaking.” An earthquake is a visible rip across the Earth’s surface due to a release of energy and stored stress in the Earth’s crust and causes seismic waves. Earthquakes have been around since the time of the earliest civilizations. Earthquakes used to be compared to the “unrest of spiritual beings.” Specifically, Aristotle and the Ancient Greeks stated that earthquakes were the result of the “underground winds”. The earliest earthquakes were recorded by seismometers which calculate the waves generated by each earthquake. The original seismometer was the Wood – Anderson seismometer. When an earthquake would occur a structure would dangle and reflect light on an image. The image “drawn” by the light reflected the amount of seismic waves caused by the earthquake. The second seismometer came in the 1930’s from Charles Richter who used a logarithm to determine the seismic waves. The current magnitude scale that appears in the media came in the 1960’s from Keitti Aki. This model takes the overall seismic movement through scientific analysis. These models have helped scientists and geologists further develop the impact of earthquakes throughout history and some of these methods are still used today (Hough 1).
The first study of earthquakes came in the 18th century after five earthquakes in England and a massive earthquake in Portugal. The idea of plate tectonics did not come for another half century ultimately providing a deeper explanation of earthquakes. Gaining further insight to the current explanation of earthquakes that are truly caused by the stress along active plate boundaries where tectonic plates converge or slide past each other relieving stored stress along the fault lin...
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Earthquakes are a natural part of the Earth’s evolution. Scientific evidence leads many geologists to believe that all of the land on Earth was at one point in time connected. Because of plate tectonic movements or earthquakes, continental drift occurred separating the one massive piece of land in to the seven major continents today. Further evidence supports this theory, starting with the Mid-Atlantic ridge, a large mass of plate tectonics, which are increasing the size of the Atlantic Ocean while shrinking the Pacific. Some scientists believe that the major plate moveme...
The Fredonia Earthquake that took place in Fredonia, Arizona on July 21st, 1959 was the largest earthquake to ever strike the state and it triggered a rockslide at Mather Point in the Grand Canyon.
Earthquakes play a major role into understanding the composition and materials that exist within the Earth (Merali and Skinner, 2009, p.252). Earthquakes are the main source of insight into the inner workings of the earth, due to the nature of the seismic waves they produce. P and S waves are reflected and refracted at different boundaries within the earth, and this enables seismologists to make inferences about the internal composition and structural of planet Earth. (Merali and Skinner, 2009, p.252).
Plummer, C.C., McGeary, D., and Carlson, D.H., 2003, Physical geology (10th Ed.): McGraw-Hill, Boston, 580 p.
Earthquakes in California are certainly not a surprise. What is a surprise is their unpredictability and randomness. Geologists say there is roughly a 50 percent chance that a magnitude 8 or more quake will hit the Los Angeles area sometime over the next 30 years. And, over the past twenty years, the Los Angeles area has witnessed several earthquakes, and in particular, two that were quite devastating; the 1971 San Fernando earthquake, and the January 17, 1994, Northridge Earthquake. Given the certainty that earthquakes will occur, they still seem to come as a surprise, and leave many communities unprepared to deal with their aftermath.
Since record keeping began, sometime in the 18th century, there have been 13 major earthquakes along the San Andreas Fault. However, radiocarbon dating has proved that earthquakes have been happening along the fault for thousands of years. The earliest recorded earthquake happened on July 28, 1769, and was experienced by Spanish explorer Gaspar de Portola while he camped along a small lake he named “San Andreas Lake”. Other notable early earthquakes occurred in 1836, 1838, 1865, 1868, and 1890. Unfortunately, there is no seismographic data recorded for these early earthquakes since it was not until 1887 that seismographs began being used in the United
Heller, Arnie. "The 1906 San Francisco Earthquake." Science & Technology (2006): 4-12. Web. 8 May 2014.
From studying the science behind the San Francisco earthquake, scientists have made a number of important discoveries involving how earthquakes function. At 5:12 on a fateful April morning in 1906, the mammoth Pacific and North American plates sheared each other at an incredible twenty-one feet along the San Andreas fault, surpassing the annual average of two inches (“San Francisco Earthquake of 1906”) (“The Great 1906 Earthquake and Fires”). A few seconds later, the destructive earthquake occurred. The ground shifted at almost five feet per second, and the shaking could be felt all the way from southern Oregon to southern Los Angeles to central Nevada (“Quick”) (“The Great 1906 San Francisco Earthquake”). In fact, the earthquake could be registered in a seismograph on Capetown, South Africa, an astounding 10,236 miles away...
Before examining the Northridge event, understanding the naturally occurring hazard that is an earthquake will help to better understand exactly what happened and why it was such an important geological event. With four distinct layers, two layers, the crust and upper portion of the mantle, compose the skin that is the surface layer of the Earth. The crust is not a single, continuous piece. It is actually several different pieces, or plates, that come together to form the puzzle that comprises the surface of the Earth. These plates are in constant motion rubbing against one another. These areas, known as fault lines, where the plates rub up against one another have spots where one plate ”gets stuck while the rest of the plate keeps moving. When the plate has moved far enough, the edges unstick and is how most of the earthquakes around the world occur” (Wald, 2012). The energy stored from the friction of the two plate...
study of the San Andreas fault system." (USGS) When the 1906 earthquake struck scientist set
An earthquake occurs abruptly and causes severs damage to people, property, landscape and more. A great mega-thrust earthquake, known as the Great Tohoku Earthquake has shaken Japan at 5:46:24 UTC on March 11, 2011. It caused a severe disaster, including tsunami and nuclear radiation exposure.. This mega-quake located at the latitude 38.297 degree North and longitude of 142.372 degree East, near the east coast of Honshu, Japan (USGS, 2013). An earthquake and tsunami waves caused widespread damage to many areas of Japan. People in Japan are still recovering from the damages.
Plate tectonics are a relatively new theory that has revolutionized the way geologists think about the Earth. According to the theory, the surface of the Earth is broken into large plates. The size and position of these plates change over time. The hypothesis of continental drift was largely developed by the German Alfred Wegener The edges of these plates, where they move against each other, are sites of intense geologic activity, such as earthquakes, volcanoes, and mountain building. Plate tectonics is a combination of two earlier ideas, continental drift and sea-floor spreading. Continental drift is the movement of continents over the Earth's surface and in their change in position relative to each other. Sea-floor spreading is the creation of new oceanic crust at mid-ocean ridges and movement of the crust away from the mid-ocean ridges. Plate Boundaries are located around the boarder of the plate. It is where the plates collide. There are different types of Boundaries, Divergent Plates transform boundary Subduction boundary and collisional boundary. A divergent boundary occurs where two plates move apart, allowing magma, or molten rock, to rise from the Earth's interior to fill in the gap. The two plates move away from each other like two conveyor belts moving in opposite directions. Plate area is increased as the plates move apart. Plate movement takes place laterally away from the plate boundary, which is normally marked by a rise or a ridge. The ridge or rise may be offset by a transform fault. Presently, most divergent margins occur along the central zone of the world's major ocean basins. The process by which the plates move apart is referred to as sea floor spreading. The Mid-Atlantic Ridge and East P...
With our increased knowledge of the ocean floor configuration and the concepts of seafloor spreading, it has supplied us with evidence for continental drift. The plate tectonics theory came to a gradual acceptance through the evolution of scientific thought and acceptance whereby the idea of mobile continents increased understanding of earthquakes and thus technology to minimise the effects.
It was a beautiful day like any other with the clear blue sky and the
Earthquakes belong to the class of most disastrous natural hazards. They result in unexpected and tremendous earth movements. These movements results from dissemination of an enormous amount of intense energy in form of seismic waves which are detected by use of seismograms. The impact of earthquakes leaves behind several landmarks including: destruction of property, extensive disruption of services like sewer and water lines, loss of life, and causes instability in both economic and social components of the affected nation (Webcache 2).