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
0
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] According to the passage, which of the following must take place in order for any earthquake to occur?
选项
A、Stress must build up.
B、Cool rock must descend into the mantle.
C、A fracture must occur.
D、Both A and C
答案
D
解析
题目问:文章表明,任何地震发生的条件是什么?第一段第二句Stress buildsup until a fracture forms at the depth of a few kilometers and the crust slips to relieve the stress.通过这句话可知,地球压力积聚,直至地壳在几千米深处断裂。据此判断,应选择D。
转载请注明原文地址:https://tihaiku.com/zcyy/4027302.html
相关试题推荐
Anxietyisbelievedto______diabetesbyraisinglevelsofthestresshormoneCor
InmostearthquakestheEarth’scrustcrackslikeporcelain.Stressbuildsu
InmostearthquakestheEarth’scrustcrackslikeporcelain.Stressbuildsu
Thenoneofstudentsintheclasslikesthemistress,whoisusedtobeing______
Hewasinextremestateofdistressanddepressionwhenheknewthathehad_____
OneofthelargestearthquakeseverrecordedhitonBoxingDay2004.Theresu
OneofthelargestearthquakeseverrecordedhitonBoxingDay2004.Theresu
OneofthelargestearthquakeseverrecordedhitonBoxingDay2004.Theresu
OneofthelargestearthquakeseverrecordedhitonBoxingDay2004.Theresu
OneofthelargestearthquakeseverrecordedhitonBoxingDay2004.Theresu
随机试题
Archaeologistshavelongthoughtthatstoneshipsservedasgravesforoneo
Nowadayspeopleusemanymethodstokeepfit.Forexample,takingexercisean
下列不属于干式系统空压机启动频繁的原因是()。A.干式系统空压机启停压力设定不
WHO提出康复服务的方式有()A.康复机构的康复 B.自我保健康复 C
依据我国《继承法》第十条的规定,作为法定继承人的兄弟姐妹不包括()。A.同父同
呼吸急促似喘,声高断续,喉间有哮鸣音者,称()A.短气 B.少气
下列哪些项是实现区域生态安全格局的途径?( )A.协调城市发展、农业与自然保护
老李对退休后的生活感到有些不适应,他的一对儿女虽然很忙,但还是经常来看望老李。老
臌胀病机是A.气滞湿阻血瘀 B.气滞血瘀水停 C.气滞血瘀 D.气滞痰凝血
某施工单位承建一立井井筒,该井筒直径6.5m,深度668m,采用立井混合作业施
最新回复
(
0
)