Earthquake
What is Earthquake?
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Any sudden extreme movement of the ground is caused by seismic waves passing through the Earth's rocks. When a kind of energy held inside the Earth's crust is released all of a sudden, typically when masses of rock burdening against one another unexpectedly crack and "slide," seismic waves are created. Geologic faults, which are confined areas where rock masses can move in relation to one another, are where earthquakes happen most frequently. The margin of the largest tectonic plates that make up the crust of the Earth are where the majority of the world's major fault lines are found.
Causes of earthquakes
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Most earthquakes are caused by movement in confined regions along plate boundaries. Divergent, convergent, and transform boundaries are where the majority of seismic activity takes place.
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Occasionally, as the plates past one another and become caught, pressure is created. The ground shakes as seismic waves are released when the plates eventually slip as a result of the rising pressure. An earthquake has occurred.
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The ocean is visible over several of the plates. In some plates, both the ocean and the continents are included. Our planet's geological characteristics are shaped in part by plate tectonic processes. Plate movements can be divided into three categories:
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Divergent (Spreading): This is the separation of two plates. Along the opening, molten rock from the mantle erupts, creating a new crust. These zones, also known as spreading centers, are prone to small earthquakes. Divergent plate motion caused the forming process of the Red Sea, the Gulf of Aden, and the Great Rift Valley in Africa.
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Convergent (Colliding): When two plates converge and clash, this is known as convergence. The thinner, denser, and more flexible oceanic plate slips beneath the thicker, more rigid continental plate when a continental plate meets an oceanic plate. It's known as subduction. The rocks dragged down beneath the continent begin to melt. Sometimes molten rock comes up to the surface and forms a line of volcanoes throughout the continent. Nearly 80% of earthquakes happen where plates collide with each other, called convergent boundaries.
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A collision where two continental plates collide is another type of convergent boundary. The plates collapse and are propelled upward since neither is stronger than the other. As a result, enormous, tall mountain ranges like the Himalayas may emerge.
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Transform boundary: A transform or lateral fault occurs at the place where two tectonic plates slide past each other. One of the best instances of lateral plate motion is the San Andreas Fault.
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Effects of Earthquakes
Ground Shaking
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The most well-known effect of earthquakes is ground shaking. It is caused by seismic waves passing through the ground and can range from fairly soft in small earthquakes to extremely severe in huge earthquakes. The trembling of the ground during an earthquake is referred to as ground shaking. Body waves and surface waves create ground shaking. In general, the severity of ground shaking increases with amplitude and decreases with distance from the causing fault. Although the physics of seismic waves is complex, ground shaking can be explained in terms of compressional and shear body waves, as well as surface waves Rayleigh and Love.
P waves travel through the Earth at approximately 15,000 miles per hour and are the first waves to cause building vibration. S waves follow, causing a structure to vibrate from side to side. They are the most damaging waves because horizontal motion damages buildings more easily than vertical motion. P and S waves are responsible for high-frequency vibrations, but Rayleigh and Love waves, which come last, are responsible for low-frequency vibrations. Body and surface waves cause the ground, and thus a building, to vibrate in a complicated way.
Landslides
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Several types of landslides have been observed to occur in association with earthquakes in the past. Rock falls and slides of rock fragments that occur on steep slopes are the most common types of earthquake-induced landslides. Shallow debris slides on steep slopes, as well as soil and rock slumps and block slides on moderate to steep slopes, occur, but are less common. Large earthquake-induced rock, soil, and submarine landslides can be extremely damaging. Avalanches form over steepened slopes in unstable rocks. One of the most dramatic incidents occurred during the 1970 Peruvian earthquake, when a single rock avalanche killed over 18,000 people; a similar, but less spectacular, failure occurred during the 1959 Hebgen Lake, Montana, earthquake, which killed 26 people. Soil avalanches occur in some fine-grained, weakly cemented materials, such as loess, which forms steep, stable slopes under non-seismic conditions. The magnitude of the earthquake, its focal depth, the terrain and geologic conditions along the causative fault, and the amplitude, frequency composition, and duration of ground shaking all influence the size of the area affected by earthquake-induced landslides.
Tsunami
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Tsunamis are water waves created by a significant region of the sea floor suddenly moving vertically during an underwater earthquake. Tsunamis are frequently referred to as tidal waves, although this is a misconception. Tsunamis, unlike typical ocean tides, are not created by the Moon and Sun's tidal motion. In the deep ocean, the height of a tsunami is normally about 1 foot, but the distance between wave crests can be extraordinarily long, more than 60 miles. The tsunami's speed reduces as the depth of the ocean drops. Tsunami speeds can exceed 430 miles per hour in the mid-Pacific, where ocean depths can approach three miles. When tsunamis reach shallow water surrounding islands or on a continental shelf, the height of the waves increases many times, reaching up to 80 feet in some cases. The large distance between wave crests precludes tsunamis from dispersing energy as breaking surf; instead, tsunamis force water levels along coast lines to rise fast.
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We cannot prevent natural earthquakes, but we can dramatically reduce their consequences by detecting hazards, creating better structures, and offering earthquake safety education. We can lessen the risk of human-caused earthquakes by planning for natural earthquakes.
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Apply safety film to windows and glass doors to avoid injury from flying glass.
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Use safety wires or straps to secure heavy appliances to walls.
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Install ledge barriers on shelves and anchor large, heavy things and breakables to the shelves directly to prevent them from falling.
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Install locks on drawers and cabinet doors to prevent spills.
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Fix filing cabinets and televisions to the wall.
