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13. GWD-10-Q4 -Q6 San Andreas Fault断层成因探析
Prior to 1965 geologists assumed
that the two giant rock plates meeting at
the San Andreas Fault generate heat
Line through friction as they grind past each
(5) other, but in 1965 Henyey found that
temperatures in drill holes near the
fault were not as elevated as had
been expected. Some geologists
wondered whether the absence of
(10) friction-generated heat could be
explained by the kinds of rock composing
the fault. Geologists’ pre-1965
assumptions concerning heat generated
in the fault were based on
(15) calculations about common varieties of
rocks, such as limestone and granite;
but “weaker” materials, such as clays,
had already been identified in samples
retrieved from the fault zone. Under
(20) normal conditions, rocks composed of
clay produce far less friction than do
other rock types.老新观点
In 1992 Byerlee tested whether
these materials would produce friction
(25) 10 to 15 kilometers below the Earth’s
surface. Byerlee found that when clay
samples were subjected to the thousands
of atmospheres of pressure
they would encounter deep inside the
(30) Earth, they produced as much friction
as was produced by other rock types.
The harder rocks push against each
other, the hotter they become; in other
words, pressure itself, not only the
(35) rocks’ properties, affects frictional
heating. Geologists therefore wondered
whether the friction between the
plates was being reduced by pockets
of pressurized water within the fault that
push the plates away from each other.新发现
现象解释
逻辑简图：
1P: prior to 1965, geologist assumed that… but in 1965 H found that… Geologists pre-1965 assumption based on….. but weaker material…
2P: 1992, B tested, found that…. In other words…. Geologists therefore wondere…
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