首页
登录
职称英语
In most earthquakes the Earth’s crust cracks like porcelain. Stress builds u
In most earthquakes the Earth’s crust cracks like porcelain. Stress builds u
游客
2025-04-05
9
管理
问题
In most earthquakes the Earth’s crust cracks like porcelain. Stress builds up until a fracture forms at the depth of a few kilometers and the crust slips to relieve the stress. Some earthquakes, however, take place hundreds of kilometers down in the Earth’s mantle, where high pressure makes rock so ductile that it flows instead of cracking, even under stress severe enough to deform it like putty. How can there be earthquakes at such depths?
That such deep events do occur has been accepted only since 1927, when the seismologist Kiyoo Wadati convincingly demonstrated their existence. Instead of comparing the arrival times of seismic waves at different locations, as earlier researchers had done, Wadati relied on a time difference between the arrival of primary(P)waves and the slower secondary(S)waves. Because P and S waves travel at different but fairly constant speeds; the interval between their arrivals increases in proportion to the distance from the earthquake focus, or a rupture point.
For most earthquakes, Wadati discovered, the interval was quite short near the epicenter, the point on the surface where shaking is the strongest. For a few events, however, the delay was long enough at the epicenter. Wadati saw a similar pattern when he analyzed data on the intensity of shaking. Most earthquakes had a small area of intense shaking, which weakened rapidly with increasing distance from the epicenter, but others were characterized by a lower peak intensity, felt over a broader area. Both the P-S intervals and the intensity patterns suggested two kinds of earthquakes: the more common shallow events, in which the focus lay just under the epicenter, and the deep events, with a focus several hundred kilometers down.
The question remained: how can such quakes occur, given that mantle rock at a depth of more than 50 kilometers is too flexible to store enough stress to fracture? Wadati’s work suggested that deep events occur in areas(now called Wadati-Benioff zones)where one crustal plate is forced under another and descends into the mantle. The descending rock is substantially cooler than the surrounding mantle and hence is less ductile and much more liable to fracture. [br] The passage is primarily concerned with______.
选项
A、demonstrating why the methods of early seismologists were flawed
B、defending a revolutionary theory about the causes of earthquakes and methods of predicting them
C、discussing the evidence for the existence of deep events and the conditions that allow them to occur
D、comparing the effects of shallow events with those of deep events
答案
C
解析
题目问:文章主要是关于什么的?通过文章内容可知,文章主要是向读者介绍deep events的知识。Wadati通过对P waves与S waves的研究发现deep events的存在。不同类型的地震其PS intervals是不同的,因此有了shallow events与deep events的区别。文章也告诉了读者deep events是如何发生的。据此判断,应选择C。
转载请注明原文地址:https://tihaiku.com/zcyy/4027300.html
相关试题推荐
InmostearthquakestheEarth’scrustcrackslikeporcelain.Stressbuildsu
InmostearthquakestheEarth’scrustcrackslikeporcelain.Stressbuildsu
Thefundisfor______distressamongthefloodvictimsinthesoutherncity.A、rel
Thefactthatthegoldeneagleusuallybuildsitsnestonsomehighcliffs______
Thefundisfor______distressamongthefloodvictimsinthesoutherncity.(20
Hewasinextremestateofdistressanddepressionwhenheknewthathehad_____
Noneofthestudentsintheclasslikesthemistress,whoisusedtobeing______
OneofthelargestearthquakeseverrecordedhitonBoxingDay2004.Theresu
OneofthelargestearthquakeseverrecordedhitonBoxingDay2004.Theresu
Mostearthquakesareinremoteareas;buteverynowandthenaquakemay______vo
随机试题
Whendidthespeakerslastseeeachother?[br][originaltext]M:Cindy!Cindyl
Questions1-6DothefollowingstatementsagreewiththeinformationgiveninRe
CITYARCHIVESAnineteenth-centurydocumentsBmapsCpersonalpapersDphotog
工作场所内外与企业安全生产缋效有关或受其影响的个人或单位,如承包商、供应商等统称
以下有关急性肠系膜上动脉栓塞的临床表现的描述中,哪项是错误的A.既往史中常有冠心
对冠心病的危险因素理解不正确的是A.可预示将来疾病的发生B.可为临床诊治疾病提供
根据下列资料回答问题。 2010年,我国进出口贸易总额为29727.6亿美元
肝硬化患者肝肾综合征的发生是由于A.肾单位纤维化 B.肾皮质坏死 C.肾髓质
蔡某女儿被夏某家的宠物犬咬成轻微伤,蔡某报警要求处罚夏某并赔偿其女儿医药费、精神
下列民事责任承担方式中,属于违约责任的有()。A.继续履行 B.赔礼道歉
最新回复
(
0
)