有同学能提供下gwd24题目的答案么，谢谢！

jiexiaodi · 发表于 2010-1-21 09:57:13

In most earthquakesthe Earth’s crust cracks like

porcelain, Stressbuilds 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 hundredsof kilometers down in the Earth’s

mantle, where high pressure makes rock soductile that

it flows instead of (10) cracking, even under stress

severe enoughto deform it like putty.How can there be

earthquakes at such depths? That such deep events do

occur hasbeen accepted only since 1927 when the

seismologist Kiyoo Wadati convincinglydemonstrated

their existence. Instead of comparing the arrival times

of seismicwaves at different locations, as earlier

researchers had done, Wadati relied ona time

difference between the arrival of primary(P) waves and

the slowersecondary(S) waves. Because P and S waves

travel at different but fairlyconstant 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 whereshaking 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 intensityof shaking. Most

earthquakes had a small area of intense shaking, which

weakened rapidly with increasing distance from the

epicenter, but others werecharacterized by a lower

peak intensity, felt over a broader area. Both the P-S

intervals and the intensity patterns suggested two kinds

of earthquakes: themore 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 quakesoccur,

given that mantle rock at a depth of more than 50

kilometers is tooductile to store enough stress to

fracture? Wadati’s work suggested that deepevents

occur in areas (now called Wadati-Benioff zones) where

one crustal plateis forced under another and descends

into the mantle. The descending rock issubstantially

cooler than the surrounding mantle and hence is less

ductile andmuch more liable to fracture.

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Q34：Thepassage is primarily concerned with

A. demonstratingwhy the methods of early seismologists were flawed

B. arguingthat deep events are poorly understood and deserve further study

C. defendinga revolutionary theory about the causes of earthquakes and methods ofpredicting them

D. discussingevidence for the existence of deep events and the conditions that allow them tooccur

E. comparingthe effects of shallow events with those of deep events

--------------------------------------------------------------------

Q35：Theauthor uses the comparisons to porcelain and putty in order to

A. explainwhy the Earth’s mantle is under great pressure

B. distinguishthe earthquake’s epicenter from its focus

C. demonstratethe conditions under which a Wadati-Benioff zone forms

D. explainwhy S waves are slower than P waves

E. illustratewhy the crust will fracture but the mantle will not

------------------------------------------------------------------

Q36：It can be inferred from the passage that ifthe S waves from an earthquake arrive at a given location long after the Pwaves, which of the following must be true?

A. Theearthquake was a deep event.

B. Theearthquake was a shallow event.

C. Theearthquake focus was distant.

D. Theearthquake focus was nearby.

E. Theearthquake had a low peak intensity.

------------------------------------------------------------------

Q37：The method used by Wadati to determine thedepths of earthquakes is most like which of the following?

A. Determiningthe depth of a well by dropping stones into the well and timing how long theytake to reach the bottom

B. Determiningthe height of a mountain by measuring the shadow it casts at different times ofthe day

C. Determiningthe distance from a thunderstorm by timing the interval between the flash of alightning bolt and the thunder it produces

D. Determiningthe distance between two points by counting the number of paces it takes tocover the distance and measuring a single pace

E. Determiningthe speed at which a car is traveling by timing how long it takes to travel aknown distance

以上几题在改版大全里面的，但是答案和分析好像缺失，不知道有没有同学能提供一下，谢谢~！

jiexiaodi · 发表于 2010-1-21 09:59:21

有乱码阿，重新贴一下文章吧：

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. 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.

有同学能提供下gwd24题目的答案么，谢谢！

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