地震的產(chǎn)生earthquake
【概述】
地震(earthquake)就是地球表層的快速振動(dòng)，在古代又稱為地動(dòng)。它就象刮風(fēng)、下雨、閃電、山崩、火山爆發(fā)一樣，是地球上經(jīng)常發(fā)生的一種自然現(xiàn)象。 它發(fā)源于地下某一點(diǎn)，該點(diǎn)稱為震源(focus)。振動(dòng)從震源傳出，在地球中傳播。地面上離震源最近的一點(diǎn)稱為震中，它是接受振動(dòng)最早的部位。大地振動(dòng)是地震最直觀、最普遍的表現(xiàn)。在海底或?yàn)I海地區(qū)發(fā)生的強(qiáng)烈地震，能引起巨大的波浪，稱為海嘯。地震是極其頻繁的，全球每年發(fā)生地震約500萬次，對(duì)整個(gè)社會(huì)有著很大的影響。
【地震的產(chǎn)生】
地震是地球內(nèi)部介質(zhì)局部發(fā)生急劇的破裂，產(chǎn)生地震波，從而在一定范圍內(nèi)引起地面振動(dòng)的現(xiàn)象。地震開始發(fā)生的地點(diǎn)稱為震源，震源正上方的地面稱為震中。破壞性地震的地面振動(dòng)最烈處稱為極震區(qū)，極震區(qū)往往也就是震中所在的地區(qū)。
【地震現(xiàn)象】
地震發(fā)生時(shí)，最基本的現(xiàn)象是地面的連續(xù)振動(dòng)，主要是明顯的晃動(dòng)。極震區(qū)的人在感到大的晃動(dòng)之前，有時(shí)首先感到上下跳動(dòng)。這是因?yàn)榈卣鸩◤牡貎?nèi)向地面?zhèn)鱽?，縱波首先到達(dá)的緣故。橫波接著產(chǎn)生大振幅的水平方向的晃動(dòng)，是造成地震災(zāi)害的主要原因。1960年智利大地震時(shí)，的晃動(dòng)持續(xù)了3分鐘。地震造成的災(zāi)害首先是破壞房屋和構(gòu)筑物，造成人畜的傷亡，如1976年中國河北唐山地震中，70％～80％的建筑物倒塌，人員傷亡慘重。地震對(duì)自然界景觀也有很大影響。最主要的后果是地面出現(xiàn)斷層和地裂縫。大地震的地表斷層常綿延幾十至幾百千米，往往具有較明顯的垂直錯(cuò)距和水平錯(cuò)距，能反映出震源處的構(gòu)造變動(dòng)特征（見濃尾大地震，舊金山大地震）。但并不是所有的地表斷裂都直接與震源的運(yùn)動(dòng)相聯(lián)系，它們也可能是由于地震波造成的次生影響。特別是地表沉積層較厚的地區(qū)，坡地邊緣、河岸和道路兩旁常出現(xiàn)地裂縫，這往往是由于地形因素，在一側(cè)沒有依托的條件下晃動(dòng)使表土松垮和崩裂。地震的晃動(dòng)使表土下沉，淺層的地下水受擠壓會(huì)沿地裂縫上升至地表，形成噴沙冒水現(xiàn)象。大地震能使局部地形改觀，或隆起，或沉降。使城鄉(xiāng)道路坼裂、鐵軌扭曲、橋梁折斷。在現(xiàn)代化城市中，由于地下管道破裂和電纜被切斷造成停水、停電和通訊受阻。煤氣、有毒氣體和放射性物質(zhì)泄漏可導(dǎo)致火災(zāi)和毒物、放射性污染等次生災(zāi)害。在山區(qū)，地震還能引起山崩和滑坡，常造成掩埋村鎮(zhèn)的慘劇。崩塌的山石堵塞江河，在上游形成地震湖。1923年日本關(guān)東大地震時(shí)，神奈川縣發(fā)生泥石流，順山谷下滑，遠(yuǎn)達(dá)5千米。
[Outlined]
Seismic (earthquake) is the rapid vibration of the Earth's surface, also known as the earth will quake in ancient times. It just as windy, rain, lightning, landslides, volcanic eruptions, often occur on Earth is a natural phenomenon. It originated from the ground floor of a point, known as the focal point (focus). Vibration from the source reported, in the dissemination of the earth. On the ground from the nearest point source called the epicenter, it is the site of the earliest to accept vibration. Vibration of the land is the most intuitive earthquake, the most common performance. Coastal areas in the submarine or the strong earthquake, can cause huge waves, called tsunami. Is extremely frequent earthquakes, global in each of the earthquake about 500 million times, the community as a whole has a GREat impact.
[A] earthquake
Earthquake is the Earth's interior local media in the rapid breakdown of a seismic wave, which in a certain range ground vibration caused the phenomenon. The earthquake started in place as the source, the source is at the top of the ground known as the epicenter. The devastating earthquake ground vibration is known as the most strong earthquake, a seismic area that is often the epicenter of the region.
[Seismic phenomena:
When the earthquake occurred, the most basic phenomenon is the continuous ground vibration, is obviously the sloshing. Most people in the earthquake zone was shaking before the large, sometimes from top to bottom was the first beating. This is because the seismic waves from the ground came to the ground, vertical landing because of the first wave. S-wave and then have a big amplitude of the horizontal direction of the sloshing, is the main reason for the earthquake disaster. 1960 Chile earthquake, the biggest shaking lasted three minutes. First of all the disasters caused by the earthquake is the destruction of homes and structures, resulting in human and animal casualties, such as the 1976 Tangshan earthquake in China's Hebei Province, 70 percent to 80 percent of the buildings collapsed, and heavy casualties. Nature of earthquakes on the landscape have GREatly affected. The main consequences on the ground to a fault and crack. The surface earthquake fault often stretching several dozen to several hundred kilometers, often have more obvious mistakes of the vertical and horizontal distance from wrong, can reflect the structural changes in the source characteristics (see strong earthquake end, the San Francisco earthquake). However, not all the fault surface and the source directly linked to the campaign, they also may be due to seismic waves caused by secondary effects. In particular the surface sediment layer thick, slope edge of the road along the river banks and often occur in cracks, which often is due to topographic factors, not relying on the side of the swaying under the conditions of the topsoil Songkua and Benglie. The earthquake shaking the surface subsidence, the shallow groundwater will be squeezed along the cracks rose to the surface, take a sandblasting water phenomenon. Earthquake local topography can change, or uplift, or settlement. So that urban and rural roads chè cracked, twisted rail tracks, bridges broken. In modern cities, because of underground pipes and cables were cut off rupture caused by water, electricity and communications disruption. Gas, toxic gas leakage of radioactive material and can lead to fires and toxic, radioactive contamination, and other secondary disasters. In the mountains, earthquakes and landslides also caused landslides, burying villages and towns often caused the tragedy. The collapse of the rocks to plug rivers, forming the upper reaches of the earthquake in the lake. 1923 Great Kanto Earthquake in Japan, the Kanagawa Prefecture in mud-rock flows, down-valley, Yuanda 5 km.