1. According to the passage, earthquake activity in the area of the Nurek reservoir is most frequent when the"the pore pressure at given depths does change when the water level fluctuates, and this is sufficient to generate seismicity."
(A) reservoir is filled to capacity
It's the fluctuation or change in water level that induces earthquakes.
(B) water level in the reservoir is exceptionally low
Same as A
(C) reservoir is subjected to sudden drops in temperature
Temperature is not a parameter for earthquakes.
(D)
water level in the reservoir fluctuatesPerfect.!
(E) water level of the reservoir area behind the dam remains constant
Same as A
2. According to the passage, which of the following proves that earthquake activity in the area of the Nurek reservoir cannot be accounted for exclusively by the composition of the rock strata underlying the reservoir?We can say that because the composition of the rock strata is the same both upstream and downstream yet there are more earthquakes upstream than downstream. Paragraph 1.
(A) There are two kinds of rock underlying the reservoir, a, but only the shallow-water limestones are permeable.
This is not the reason. Also, there is only one kind of rock underlying the reservoir.
(B)
The same rock strata underlie the whole reservoir ‘area, but only one part of the area is subject to earthquake activity.In-line with our pre-thinking.
(C) The earthquake activity in the area is evenly distributed between the regions behind the dam and the central portion of the reservoir.
This we already know and is not the reason we are looking for.
(D) The vertical load exhorted by the water in the reservoir has different effects on shallow-water limestones than on mixed shale and gypsum.
Same as A.
(E) When the frequency of earthquake activity increases, the locations of such activity become more diffuse.
This is vague and not the reason. Also we cannot deduce that.
3. Which of the following sets of causes and effects most closely parallels reservoir-induced seismicity as it is described in the passage?(A) Environmental stresses in an area combine to produce an effect; the introduction of an artifact to that area restructures the stresses and reduces the incidence of the effect.
Environmental stresses in an area combine to produce an effect - Not true.
It's the reservoir (an artifact) that induces the effect.
(B) An artifact is introduced into a stable environment; the environmental effects of that artifact cannot be separated from general environmental change.
First part is right.
the environmental effects of that artifact cannot be separated from general environmental change. - that's not true because the environmental effects of the artifact change in the level of water accumulation is not general environmental change, so it can be separated.
(C) An artifact is introduced into an environment; local conditions peculiar to that environment have little impact on the effects generally produced by such artifacts.
local conditions peculiar to that environment have little impact on the effects generally produced by such artifacts. - not true.
The composition of the rock strata has a big role in the effects produced by such artifacts.
(D) An artifact creates certain initial effects on its environment; these environmental effects are gradually mitigated by environmental adaptation to the artifact.
Not at all true.
(E)
An artifact is introduced into an environment; the artifact generates spatially uniform stress but the environment responds differentially to that stress.An artifact is introduced into an environment: Addition of reservoir.
the artifact generates spatially uniform stress but the environment responds differentially to that stress.: Upstream environment reacts differently to the stress than the same stress applied downstream.
4. Which of the following best describes the interaction of water and rock strata in the region of the anticline under the Nurek reservoir?We are talking about the inverted V shape which is found upstream of the reservoir.
(A) Shale and gypsum form the top layer of rock in an anticline and thus the water cannot penetrate to the permeable limestone layer.
That's not the rock composition we have and if anything it's just the opposite.
(B) Fractured and highly permeable limestone forms a basin in an anticline through which water penetrates to the rock below.
Fractured and highly permeable limestone forms a basin: This is the same downstream also. We have better option to define it in D.
(C) The shale and gypsum layer beneath the permeable limestone basin in an anticline prevents water from penetrating to deeper rock strata.
Same as A.
(D)
The shape of an anticline allows water to travel along with the permeable layer and penetrate into deep rock strataAs discussed in the passage this sums up everything.
(E) The structure of limestone strata alternating with shale and gypsum strata in an anticline allows the region to collect handhold water, thus increasing the load on the rocks below.
This is in V-shaped structure that is downstream.
5. It can be inferred from the passage that an accurate prediction of reservoir-induced earthquake activity at the site of the Nurek reservoir prior to its construction would have required all the following data EXCEPT(A) a general geological survey of the area, establishing the lithological composition of the rock strata
Already discussed so yes.
(B) a detailed examination of the structure of the rock strata underlying the site of the reservoir
Already discussed so yes.
(C) a projection of the number and magnitude of the fluctuations in the level of the water in the reservoir
Already discussed so yes.
(D) an estimate of the load that would be created by the total mass of water in the reservoir
Already discussed so yes.
(E)
a determination of the chemical properties of the water that would be used to fill the reservoirIt has not been discussed in the passage.
6. The passage implies that which of the following would be true in the area of the Nurek reservoir if the rate of change in the water level in the reservoir were very gradual?It was a close call between B and C but I am going with B for two reasons:
1) Refer to question 1, its just asking the same thing other way round.
2) I am thinking of this situation as Standard Deviation so if reduce the gradual change in water level(subtraction) SD should remain the same.
(A) Stress patterns in the rock strata beneath the reservoir would be the same as before its construction.
We cannot deduce that and even if we can it won't be the same as the condition before the construction.
(B)
The seismic activity beneath the reservoir would not be very frequent.(C) The spatial distribution of seismic activity beneath the reservoir would be altered.
(D) The rate of infiltration into rock strata below the reservoir would increase.
We cannot deduce that.
(E) The stress patterns in the rocks underlying the reservoir would be less affected by vertical load.
Stress patterns were not affected by the vertical load previously so it won't really matter when the water level is reduced.