题目内容

The magnitude 7.9 quake struck Sichuan province on May 12 at around noontime, which may have increased the human death toll because many people were at school, and the school buildings turned out to be not firm enough to collapse because of poor construction. More than 69,000 people have been confirmed dead so far, and more than 374,000 injured, with fears of further disasters because several lakes created by rockfall dams may give way and cause sudden flooding.

Clark Burchfiel, Schlumberger Professor of Geology, and Leigh Royden, professor of geology and geophysics in the Department of Earth, Atmospheric and Planetary Sciences at MIT, have been doing extensive research in that region of China and the Tibetan plateau(高原) for more than two decades, but had found no signs that suggested such a large earthquake might strike the area.

The team operated 25 broadband seismograph (地震仪) stations in this region of western Sichuan for more than a year. "Nobody was thinking there would be a major earthquake in that area," Royden says. "This earthquake was quite unusual, and may have involved a simultaneously（同时发生的） severe break of two separate but neighboring faults," she continued.

The region is extremely unusual geologically, Royden says, because of the very steep slopes at the boundary between the Sichuan Basin to the east and the Tibetan plateau to the west. The altitude rises sharply by about 3,500 meters (more than two miles) over a span of only about 50 kilometers (about 30 miles).

The area where the quake occurred is part of the boundary between two of the Earth's structural plates, where the Indian and Asian plates meet in an ongoing collision that has created the Himalayan mountains and the Tibetan plateau. But in central and eastern Tibet, unlike most other areas of continental collision, much of the movement of crust（地壳） is hidden from view. Instead of thickening the entire crust by folding and faulting, the surface of the eastern Tibetan plateau is not deformed（变形的） and is being lifted upward by thickening of a weak crustal layer more than 15 km below the surface.

60. Why did the school buildings collapse in the earthquake, according to the passage?

A. They had too long a history.

B. They were poorly built.

C. They were crowded with students and teachers.

D. They were damaged by the earthquake.

61. Based on Para. 1, why does the writer think that more people will be killed or injured after

the earthquake?

A. Because there will be more aftershocks after the major quake.

B. Because more school buildings will collapse after the quake.

C. Because destructive flooding caused by rockfall dams is likely to occur..

D. Because there was not enough medical care for the injured in the area.

62. What can we infer from this passage?