大全79第6题答案质疑

Passage 79 (16/22)

In most earthquakes the Earth’s crust cracks like porcelain. Stress builds up (build up: v.树立, 增进, 增大) until a fracture forms at a 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 (in proportion to: adv.与...成比例) the distance from the earthquake focus (earthquake focus: 震源), or rupture point.

For most earthquakes, Wadati discovered, the interval was quite short near the epicenter (epicenter: n.震中, 中心), 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 (in view of (in view of: adv.考虑到, 由于): CONSIDERING “given what she knew about others' lives, how could she complain about her own? Marilyn F.”) 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.

6.     The passage suggests that which of the following must take place in order for any earthquake to occur?

I.         Stress must build up.

II.     Cool rock must descend into the mantle.

III.   A fracture must occur.

(A) I only

(B) II only

(C) III only

(D) I and III only（D）

(E) I, II, and III

我怎么觉得是A呀.第一段明确说Some earthquakes, ..., where high pressure makes rock so ductile that it flows instead of cracking.就是说不断裂呀.

The passage suggests that which of the following must take place in order for ANY earthquake to occur?

be careful with "any"

6.     The passage suggests that which of the following must take place in order for any earthquake to occur?

I.      Stress must build up.

II.     Cool rock must descend into the mantle.

III.   A fracture must occur.

(A) I only

(B) II only

(C) III only

(D) I and III only（D）

(E) I, II, and III

这题我也选a,因为III在deep event里并没有发生阿，只是说‘deform  it like putty’没有crack 和fracture，为什么答案d?

The question remained: how can such quakes occur, given (in view of (in view of: adv.考虑到, 由于): CONSIDERING “given what she knew about others' lives, how could she complain about her own? Marilyn F.”) 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.

此最后一段就是解释这种不寻常的quake 是怎么发生的,hence is less ductile and much more liable to fracture.说明such quake还是有较容易fracture 的部位,最终还是能fracture的.这是 我的观点