GWD 24-35,RC

夏雨霏霏

In most earthquakes the Earth’s crust cracks likeporcelain, Stress builds up until a fracture forms at a depth of a few kilometers and the crust (5) 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 (10) 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 initial rupture point.

For most earthquakes, Wadati discovered, the interval was quite short near the epicenter; the point on the surface where shaking is strongest. For a few events, however, the delay was long even 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 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 ductile 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.
Q35：The author uses the comparisons to porcelain and putty in order to



A.explain why the Earth’s mantle is under great pressure

B.distinguish the earthquake’s epicenter from its focus

C.demonstrate the conditions under which a Wadati-Benioff zone forms

D.explain why S waves are slower than P waves

E.illustrate why the crust will fracture but the mantle will not

这道题我找不到定位阿



Q35：The author uses the comparisons to porcelain and putty in order to



A.explain why the Earth’s mantle is under great pressure

B.distinguish the earthquake’s epicenter from its focus

C.demonstrate the conditions under which a Wadati-Benioff zone forms

D.explain why S waves are slower than P waves

E.illustrate why the crust will fracture but the mantle will not

这道题我找不到定位阿

夏雨霏霏

ding!

AaronYao

In most earthquakes the Earth’s crust cracks like porcelain, Stress builds up until a fracture forms at a depth of a few kilometers and the crust (5) 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 (10) cracking, even under stress severe enough to deform it like putty.

这题定位后是要理解句子意思，不是单纯定位完就OK了，一个porcelain说明crust很容易就碎了，但putty是说明rocks in mantle易碎么？不是，根据 even under stress severe enough to deform it like putty可知，putty的意思的是说即使有很大的压力，rocks in mantle 也是很柔软不易碎的，那么举例putty就是为了说明rocks in mantle 不易碎

A.explain why the Earth’s mantle is under great pressure
文章只说了压力很大，并没有说为什么压力很大
B.distinguish the earthquake’s epicenter from its focus
epicenter和focus是下文的内容，定位错，而且在这里也没区别
C.demonstrate the conditions under which a Wadati-Benioff zone forms
Wadati-Benioff zone是下文定义的内容，定位错
D.explain why S waves are slower than P waves
s,p waves均是下文的内容，定位错，而且文章也没有解释为什么慢
E.illustrate why the crust will fracture but the mantle will not
文章开头两句都是在说明这个道理，第一句说crust易碎是因为压力叠加到了到了crust然后就是释放出来了，however，深层次的石头由于强压使其变得柔软而不易碎，即使有强大的压力足以压碎这些石头
这些in order to题除了要定位，还要明白定位所在位置在说什么，问题的目的也就是问作者所表达的意思或者要说明的事物