A Great Quake Coming
Everyone who lives in San Francisco knows that earthquakes are common in the bav area.Theyhad keen devastating in 1906，for example，a major quake destroyed about 28.000 buildings andkilled hundreds，perhaps thousands of people. Residents now wonder when the next"big one"willstrike.Its bound to happen someday.At least seven active fault(斷層)lines run through the SanFrancisco area.Faults are places where pieces of earths crust(地殼)slide past each other.Whenthese pieces slip，the ground shakes.
To prepare for that day.scientists are using new techniques to reanalyze the 1906 earthquake and predict how bad the damage might be when the next one happens. One new finding about the 1906 quake is that the San Andreas Fault split apart faster than scientists had assumed at the time.During small earthquakes，faults rupture at about 2.7 kilometersper second.During bigger quakes，however，ruptures can happen at rates faster than 3.5 kilometersper second.
At such high speeds，massive amounts of pressure build up，generating underground waves that can cause more damage than the quake itself.Lucky for San Fancisco，these pressure pulses(脈沖) traveled alway from the city duffng the 1906 event.As bad as the damage was，it could have been farWorse.
Looking ahead，scientists are trying to predict when the next major quake will occur.Records show that earthquakes were common before 1906 event. Since then，the area has been relatively quiet.Pattems in the data，however，suggest that the probability of a major earthquake striking the bay area before 2032 is at least 62 percent.
New buildings in san Francisco are quite safe in case of future quakes.Still，more than 84 percent of the citys buildings are old and weak.Analyses suggest that another massive earthquake would cause extensive damage.
People who live there today tend to feel safe because San Francisco has remained pretty qmet for a while.Accoeding to the new research，however，its not a matter of whether the big one will hit. Its just a matter of when.
16. The San Francisco area is located above several active fault lines.
A.right
B.wrong
C.not mentiond
17.The 1906 earthquake in San Francisco is the most severe one in American history.
A.fight
B.wrong
C.not mentioned
18.The highest speed of fault ruptures in the 1906 quake was more than 3.5 kilometers per second
A.fight
B.wrong
C.not mentioned
19.Earthquakes rarely happened in San Francisco before 1906.
A.fight
B.wrong
C.not mentioned
20.San Francisco is fully prepared for another big earthquake.
A.right
B.wrong
C.not mentioned
21.Scientists will be able to predict the exact time of an earthquake soon.
A.right
B.wrong
C.not mentioned
22.A major earthquake striking San Francisco someday is inevitable.
A.right
B.wrong
C.not mentiond
答案：A C A B B C A