About Earthquakes
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Earthquakes in the Philippines
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The Philippines, officially known as the Republic of the Philippines, is a sovereign island in Southeast Asia situated in the western Pacific Ocean, consisting of 7,107 islands. The Philippines’ location on the Pacific Ring of Fire and its close distance from the equator makes the Philippines prone to earthquakes and typhoons. Underneath the Phillipines, to the East, lies a tectonic plate called the Philippine Sea Plate. What is an Earthquake and how is it caused? Earthquakes are the vibrations, known as seismic waves, caused by the rocks underground suddenly breaking along a fault plane. A fault plane is a relatively flat break in the rocks that make up the Earth's crust, along which rocks on either side have moved past each other. Because these surfaces are rough, rocks that meet along a fault do not slide easily past each other, but are instead locked for long periods by friction. Over thousands of years, strain builds up within the rocks that are separated by the fault as their movement is prevented. At some point, the amount of strain exceeds the forces that are preventing slip. The fault ruptures and rocks on either side of the fault slide rapidly as the built-up strain is relieved. The moment of rupture is when the earthquake occurs. MAP OF PHILIPPINES AND ITS EARTHQUAKES
What is the process of an Earthquake? The seismic "cycle" refers to the observation that earthquakes repeatedly rupture a given part of a fault. The term "cycle" does not however imply that earthquakes are a regularly repeating or periodic event. The seismic cycle can be divided into three periods, consisting of inter-seismic slip, co-seismic slip, and post-seismic slip. Inter-seismic slip refers to the strain that accumulates steadily between the earthquakes that repeatedly but irregularly rupture the fault. In general, measurements of the motion of two sites within a year that are located immediately across the fault from each other will show little or no motion.This is because the fault is locked between earthquakes and the crust adjacent to the fault thus cannot slip. Co-seismic slip refers to the slip that occurs at the instant of the earthquake. Measurements of co-seismic motion for site near and far from the fault show the opposite pattern as exhibited for inter-seismic motion. During an earthquake, the highly strained rocks near the fault rupture, which moved little or not at all during the inter-seismic period, are permitted to slide back to a less-strained state. Post-seismic slip refers to slip that occurs in the days, months, and sometimes years after an earthquake. Such slips occur for a variety of reasons and typically differs from the steady inter-seismic slip. A fault that has experienced a significant rupture often continues to accommodate significant slip after the rupture. However, the post-seismic slip eventually decays back to the steady inter-seismic slip. What are the effects of an Earthquake? Most earthquake-related deaths are caused by the collapse of structures and the construction practices play a tremendous role in the death toll of an earthquake. Building practices can make all the difference in earthquakes, even a moderate rupture beneath a city with structures unprepared for shaking can produce tens of thousands of casualties. Although probably the most important, direct shaking effects are not the only hazard associated with earthquakes, other effects such as landslides, liquefaction, and tsunamis have also played important part in destruction produced by earthquakes. What are the impacts of earthquakes on society? An earthquake hazard poses the most serious intermediate term risk to the health, safety, and economic viability of many parts of the world. Earthquakes can leave devastating effects, including both physical and emotional pain and trauma, claiming thousands of lives each year, leaving thousands of families grieving loved ones. Few natural disasters can match the destructive power of earthquakes. Often striking with little notice, these events can reduce entire cities to rubble in mere minutes. In addition to causing widespread deaths and casualties, earthquakes can also disrupt a country's infrastructure, making aid operations and rescue missions particularly difficult. This all causes many hardships to people already struggling.with the burden of an earthquake. What are an earthquakes effects on the atmosphere, biosphere, lithosphere and stratosphere?
Effects on the Atmosphere Methane is a toxic gas that when released into the atmosphere ,can cause a large amount of damage. Methane is a form of fossil fuel pollution that after a while begins to create openings in the ozone layer therefore exposing us to harsh and threatening UV rays. Methane is the aftermath of an organic material or substance decomposing, methane can also be found exuding through the sea floor. Most of the time the decomposed organic material mixes with the salty ocean water and creates gas hydrates which is a substance that is alike cement or ice that lays at the bottom of the sea blocking off any methane seepage. Although when an earthquake occurs it causes the cement like barrier to slowly crack and shatter therefore allowing the methane to seep through polluting the ocean and the atmosphere. Effects on the Biosphere Earthquakes have an enormous negative impact on the biosphere. As a consequence of the ground shaking quite recklessly and rapidly, it causes many crops to fall apart and deteriorate. Most trees, vines and shrubs are forced out of the ground, roots and all. The harsh and rapid shaking of the ground can also cause ecosystems to be disrupted and sometimes destroyed. Effects on the Lithosphere Earthquakes mainly occur in the outer layer of the Earth, called the Lithosphere. The lithosphere is made up of the Earth's crust and upper mantle. It is quite fragile and vulnerable to brittle failure. As a result of earthquakes rapidly rupturing and shaking the Earth’s surface the lithosphere is constantly strained and deforms and deteriorates slowly over a certain time span as certain areas of the lithosphere become extremely weak and tear. Effects on the Hydrosphere Earthquakes have many negative impacts on the hydrosphere. One for instance is the formation of tsunamis. Destructive tsunamis are generated from large, shallow earthquakes with an epicenter or fault line near or on the ocean floor. A small wave, generally only a few feet tall, is generated. As the depth of water decreases near land, however, the height of the wave increases many times, and is capable of causing massive destruction hundreds or thousands of miles from the site of the earthquake. A miniature form of tsunami that can occur in lakes is called a seiche. Earthquakes may also modify groundwater flow from springs by causing expansion and contraction of the aquifer from which the spring flows. The change may be either temporary or permanent. Earthquake faults may also result in water that collects in the depression along a strike-slip fault line. |