[求助]gwd 24-32

caicaizifore

    

 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.

    

GWD-24-32.

    

The passage supports which of the following statements about the
relationship between the epicenter and the focus of an earthquake?

    

 

    

A.      P waves originate at the
focus and S waves originate at the epicenter.

    

B.       In deep events the
epicenter and the focus are reversed.

    

C.     
In shallow events the epicenter and the focus
coincide

    

D.     
In both deep and
shallow events the focus lies beneath the epicenter

    

E.       The epicenter is in the
crust, whereas the focus is in the mantle.

我选了C，答案说是d，怎么看d都是错的嘛，因为文中说到

the more common shallow events, in which the focus lay just under
the epicenter, and deep events, with a focus several hundred kilometers down.

求教！！！！谢谢！

caicaizifore

我想明白了，原来是看错题的意思了，不好意思