In 1971 researchers hoping to predict earthquakes in the short term by identifying precursory phenomena (those that occur a few days before large quakes but not otherwise) turned their attention to changes in seismic waves that had been detected prior to earthquakes. An explanation for such changes was offered by “dilatancy theory,” based on a well-known phenomenon observed in rocks in the laboratory: as stress builds, microfractures in rock close, decreasing the rock’s volume. But as stress continues to increase, the rock begins to crack and expand in volume, allowing groundwater to seep in, weakening the rock. According to this theory, such effects could lead to several precursory phenomena in the field, including a change in the velocity of seismic waves, and an increase in small, nearby tremors. Researchers initially reported success in identifying these possible precursors, but subsequent analyses of their data proved disheartening. Seismic waves with unusual velocities were recorded before some earthquakes, but while the historical record confirms that most large earthquakes are preceded by minor tremors, these foreshocks indicate nothing about the magnitude of an impending quake and are indistinguishable from other minor tremors that occur without large earthquakes. In the 1980s, some researchers turned their efforts from short-term to long-term prediction. Noting that earthquakes tend to occur repeatedly in certain regions, Lindh and Baker attempted to identify patterns of recurrence, or earthquake cycles, on which to base predictions. In a study of earthquake-prone sites along the San Andreas Fault, they determined that quakes occurred at intervals of approximately 22 years near one site and concluded that there was a 95 percent probability of an earthquake in that area by 1992. The earthquake did not occur within the time frame predicted, however. Evidence against the kind of regular earthquake cycles that Lindh and Baker tried to establish has come from a relatively new field, paleoseismology. Paleoseismologists have unearthed and dated geological features such as fault scarps that were caused by earthquakes thousands of years ago. They have determined that the average interval between ten earthquakes that took place at one site along the San Andreas Fault in the past two millennia was 132 years, but individual intervals ranged greatly, from 44 to 332 years. 1 (Book Question: 11) 1. The passage is primarily concerned with A. explaining why one method of earthquake prediction has proven more practicable than an alternative method B. suggesting that accurate earthquake forecasting must combine elements of long-term and short-term prediction C. challenging the usefulness of dilatancy theory for explaining the occurrence of precursory phenomena D. discussing the deficiency of two methods by which researchers have attempted to predict the occurrence of earthquakes E. describing the development of methods for establishing patterns in the occurrence of past earthquakes 2 (Book Question: 12) 2. According to the passage, laboratory evidence concerning the effects of stress on rocks might help account for A. differences in magnitude among earthquakes B. certain phenomena that occur prior to earthquakes C. variations in the intervals between earthquakes in a particular area D. differences in the frequency with which earthquakes occur in various areas E. the unreliability of short-term earthquake predictions 3 (Book Question: 13) 3. It can be inferred from the passage that one problem with using precursory phenomena to predict earthquakes is that minor tremors A. typically occur some distance from the sites of the large earthquakes that follow them B. are directly linked to the mechanisms that cause earthquakes C. are difficult to distinguish from major tremors D. have proven difficult to measure accurately E. are not always followed by large earthquakes 4 (Book Question: 14) 4. According to the passage, some researchers based their research about long-term earthquake prediction on which of the following facts? A. The historical record confirms that most earthquakes have been preceded by minor tremors. B. The average interval between earthquakes in one region of the San Andreas Fault is 132 years. C. Some regions tend to be the site of numerous earthquakes over the course of many years. D. Changes in the volume of rock can occur as a result of building stress and can lead to the weakening of rock. E. Paleoseismologists have been able to unearth and date geological features caused by past earthquakes. 5 (Book Question: 15) 5. The passage suggests which of the following about the paleoseismologists’ findings described in lines 42–50? A. They suggest that the frequency with which earthquakes occurred at a particular site decreased significantly over the past two millennia. B. They suggest that paleoseismologists may someday be able to make reasonably accurate long-term earthquake predictions. C. They suggest that researchers may someday be able to determine which past occurrences of minor tremors were actually followed by large earthquakes. D. They suggest that the recurrence of earthquakes in earthquake-prone sites is too irregular to serve as a basis for earthquake prediction. E. They indicate that researchers attempting to develop long-term methods of earthquake prediction have overlooked important evidence concerning the causes of earthquakes. 6 (Book Question: 16) 6. The author implies which of the following about the ability of the researchers mentioned in line 18 to predict earthquakes? A. They can identify when an earthquake is likely to occur but not how large it will be. B. They can identify the regions where earthquakes are likely to occur but not when they will occur. C. They are unable to determine either the time or the place that earthquakes are likely to occur. D. They are likely to be more accurate at short-term earthquake prediction than at long-term earthquake prediction. E. They can determine the regions where earthquakes have occurred in the past but not the regions where they are likely to occur in the future.

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In 1971 researchers hoping to predict earthquakes in the short term by

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16 Apr 2020, 07:52

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jayarora

Hi, could someone help explain Question 4 please?

The relevant portion of the passage:

Paleoseismologists
have unearthed and dated geological features
such as fault scarps that were caused by
earthquakes thousands of years ago. They have
determined that the average interval between ten
earthquakes that took place at one site along the
San Andreas Fault in the past two millennia was
132 years, but individual intervals ranged greatly,
from 44 to 332 years.
Now if the time period has increased from 22 years(as predicted by L and B) to 132, why cannot we infer that the frequency has significantly reduced? Wouldn't choice A be a correct answer?

Thanks in advance

Hi Jay

I think you refer to Q5 and not Q4.

Option (A) states that "frequency with which earthquakes occurred at a particular site decreased significantly over the past two millennia". There are several problems with this:

1) The passage suggests that Lindh and Baker's predictions did not pan out.
2) Recent findings of paleoseismologists show a greater gap between earthquakes.

The recent findings seem to overturn the earlier suggestions ie; it is the research findings that have changed the time interval - the actual time interval would have been the same irrespective of the research findings. Therefore it would be inaccurate to say, based on these statements, that the "frequency of earthquakes...has decreased" as option (A) does. We can also surmise this from the statement, " the average interval between ten earthquakes that took place at one site along the San Andreas Fault in the past two millennia was 132 years, but individual intervals ranged greatly, from 44 to 332 years". This implies that there was no regular trend in the time interval between successive earthquakes - there has been variation but there is nothing to suggest whether the time interval has been increasing or reducing.

Hope this helps.

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VeritasKarishma GMATNinja
can u explain last question and also this line(earthquakes, but while the historical record confirms
that most large earthquakes are preceded by minor
tremors,) why 2 contradictory words are used together.
In 5 question if option d wasn't mentioned can we say E option be correct though it isn't mentioned whether they looked or not looked on causes of earthquake ,but paleoseismologists looked at the causes.

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18 Jun 2020, 19:55

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Quote:

The author implies which of the following about the ability of the researchers mentioned in line 18 to predict earthquakes?

A. They can identify when an earthquake is likely to occur but not how large it will be.
B. They can identify the regions where earthquakes are likely to occur but not when they will occur.
C. They are unable to determine either the time or the place that earthquakes are likely to occur.
D. They are likely to be more accurate at short-term earthquake prediction than at long-term earthquake prediction.
E. They can determine the regions where earthquakes have occurred in the past but not the regions where they are likely to occur in the future.

in E option:
but not the regions where they are likely to occur in the future.= TRUE
They can determine the regions where earthquakes have occurred in the past =?

Quote:

Statement1: . They have determined that the average interval between ten earthquakes that took place at one site along the San Andreas Fault in the past two millennia was 132 years, but individual intervals ranged greatly, from 44 to 332 years

.
>> They can only determine if they know where these earthquakes have occurred

Quote:

Statement2:In a study of earthquake-prone sites along the San Andreas Fault, they determined that quakes occurred at intervals of approximately 22 years near one site and concluded that there was a 95 percent probability of an earthquake in that area by 1992

>> They determined where these earthquakes occurred
atleast they have some ability to determine the earth quake location where it occured . it could be anywhere between 0.xx% to 99.xx%

The long term prediction analysis is based on history of these earthquake occurrences ,so we can't determine that they have no ability.

If i see the question:

Quote:

about the ability of the researchers mentioned in line 18 to predict earthquakes

In 1971 researchers hoping to predict earthquakes - researchers A
In the 1980s, some researchers turned their efforts from short-term to long-term prediction.- Some researchers subset of A
so could be same researchers

Quote:

C. They are unable to determine either the time or the place that earthquakes are LIKELY to occur.

LIKELY- it doesn't say MUST BE.
Likely could be anywhere between 0.xx-99.xx%.

After this detailed understanding, why would i chose answer C?
GMATGodGMATNinja @GMATNinjaTwo neetis5 Kurtosis abhimahna Skywalker18 aragonn MentorTutoring CrackVerbalGMAT VeritasKarishma

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19 Jun 2020, 04:32

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Hello, SkR1. I enjoyed reading your thorough analysis. I feel honored to have been mentioned alongside the others you named. I typically add my two cents when I feel a more thorough treatment of a question may be warranted, or if a user brings up a specific point that has not been addressed. I do this out of respect for my fellow GMAT Clubbers, Experts and students alike. In this case, I see that the top two posts in the thread address this very question. If you have read through the analyses by GMATNinjaTwo, neetis5, smartyman, Kurtosis, abhimahna, sahilbhatia21 at the top of page 2, and Chelsea212 and the question still does not make sense, then feel free to ask again for help. I guess I am having trouble understanding any lingering doubts you may have. (And, to be honest, I feel I have little to add in the way of insight that the posts above by the aforementioned members have not already touched on.)

Thank you for tagging me. I hope you find the answer you are looking for.

- Andrew

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21 Jun 2020, 05:12

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saby1410

Yes, question no 6 is certainly a bit tricky and it took me a couple of reads before I settled on (C).

Lines of interest:
In 1971 researchers hoping to predict earthquakes in
the short term by identifying precursory phenomena
(those that occur a few days before large quakes
but not otherwise) turned their attention to changes
(5)
in seismic waves...

...

Researchers initially reported success in identifying
these possible precursors, but subsequent analyses
of their data proved disheartening. Seismic waves
(20)
with unusual velocities were recorded before some
earthquakes, but while the historical record confirms
that most large earthquakes are preceded by minor
tremors, these foreshocks indicate nothing about
the magnitude of an impending quake and are
(25)
indistinguishable from other minor tremors that occur
without large earthquakes.

In the 1980s, some researchers turned their
efforts from short-term to long-term prediction.

So in 1971, researchers thought of predicting earthquakes in short term by identifying precursory phenomena (such as, rain before a rainbow).
They observed some changes in seismic waves before large earthquakes. Initially, they reported success (say, they observed that before every large earthquake, these seismic waves changed) but later were disappointed. They observed these changes in seismic waves before small earthquakes as well as without any earthquakes. So now can they predict when an earthquake will happen based on changes in seismic waves? No. Some times these changes lead to large earthquakes, sometimes to small earthquakes and sometimes to no earthquake. So if we see these changes, can we say whether an earthquake will happen? No.
In 1980s, some researchers turned away from predicting short term and tried to predict long term earthquakes. After this we have the discussion on places that are earthquake prone etc.

6. The author implies which of the following about the ability of the researchers mentioned in line 18 to predict earthquakes?

A. They can identify when an earthquake is likely to occur but not how large it will be.

Changes in seismic waves can take place even without earthquakes. Apparently they are frequent enough to make researchers consider it a failure and turn away. Hence, they cannot identify when an earthquake is likely to occur.

C. They are unable to determine either the time or the place that earthquakes are likely to occur.

Correct. The researchers mentioned in line 18 give no lead on predicting earthquakes in any way.

Answer (C)

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21 Jun 2020, 05:20

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saby1410

As for your 'but while' question, notice the structure of the sentence:

Clause A - Seismic waves with unusual velocities were recorded before some earthquakes.

Clause B - While the historical record confirms that most large earthquakes are preceded by minor tremors, these foreshocks indicate nothing about the magnitude of an impending quake and are indistinguishable from other minor tremors that occur without large earthquakes.

'But' joins these two contrasting independent sentences.

Clause A, but Clause B

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saby1410

As for question 5, option (E) is not correct and will not be. The passage doesn't suggest it. No one suggests anything about 'causes of earthquakes'.

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Hi experts GMATNinjaTwo GMATNinja

Can someone explain, why D is correct in question 5?

Thanks!

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Question 5

Adambhau

Hi experts GMATNinjaTwo GMATNinja

Can someone explain, why D is correct in question 5?

Thanks!

Question 5 asks about some findings described in lines 42-50. Before diving into those exact lines, however, it's important to understand the broader context of that piece of the passage. Why is the author talking about the findings in the first place?

In the third paragraph, the author introduces the idea of "earthquake cycles." If earthquakes happened at regular intervals, that would be incredibly helpful in predicting when the next earthquake would occur.

But then, in the fourth paragraph, the author introduces evidence against the existence of regular earthquake cycles. This evidence comes from paleoseismologists, and their findings are described in lines 42-50:

"Paleoseismologists have unearthed and dated geological features such as fault scarps that were caused by earthquakes thousands of years ago. They have determined that the average interval between ten earthquakes that took place at one site along the San Andreas Fault in the past two millennia was 132 years, but individual intervals ranged greatly, from 44 to 332 years.

Overall, this evidence shows that earthquake cycles aren't particularly useful in predicting exactly when the next earthquake will come around -- if someone told you that an earthquake will strike sometime within the next 44 to 332 years, you probably wouldn't find that to be a super helpful prediction.

This is captured perfectly in (D): the paleoseismologists' work suggests that "the recurrence of earthquakes in earthquake-prone sites is too irregular to serve as a basis for earthquake prediction."

(D) is the correct answer to question 5.

I hope that helps!

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Hi stonecold, good question!

Quote:

I have a query regarding the last question in this series.
We are asked about the ability of the researchers in the line 18.
The passage clearly indicates and even mentions -> They were able to predict the timing but not the magnitude." indistinguishable from other minor tremors that occur"

I am still convinced that the OA should be A.

What am i missing.?

P.S-> I have seen the other replies.
without large earthquakes.

Imagine that the researchers recorded 100 large earthquakes of various magnitudes during their study and that nearly all of those large earthquakes were preceded by minor tremors. This might lead us to expect any minor tremor to be followed by a large earthquake, even though we might not know exactly how large that "large" earthquake will be. Thus, choice A is tempting.

Now consider the final fact given in line 23: "these foreshocks... are indistinguishable from other minor tremors that occur without large earthquakes." If instead the passage stated, "these foreshocks are indistinguishable from other minor tremors that occur before small earthquakes", THEN choice A would be defensible... this would imply that after a minor tremor we can expect an earthquake, though we have no idea how small or large it will be. But the passage states that the tremors are "indistinguishable from other minor tremors that occur without large earthquakes." Therefore, the passage implies that a minor tremor could be followed by a large earthquake, a small earthquake, or no earthquake at all; for example, the researchers may have recorded HUNDREDS of minor tremors that were NOT followed by an earthquake.

This explanation is supported by the first sentence starting in line 17: "Researchers initially reported success in identifying these possible precursors, but subsequent analyses of their data proved disheartening." In other words, the researchers were initially successful in identifying earthquake precursors; subsequent analyses proved disheartening, implying that the researchers were not successful in identifying precursors that would predict earthquakes.

I hope that helps!

So where my confusions lies is that the passage explicitly states "without large earthquakes." Now the question isn't asking about large earthquakes but earthquakes in general, so as such I interpreted the passage to mean that the tremors aren't correlated with magnitude but are correlated with an earthquake, large or small, and as a result I thought A was the correct answer. If the question choice had mentioned "LARGE" earthquakes specifically I likely would have went with C instead of A.

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dylanl1218

GMATNinjaTwo

Hi stonecold, good question!

Quote:

The problem is that “without large earthquakes” does not necessarily imply that a small earthquake occurs. It’s equally likely that no earthquake occurs. For (A) to be correct, we’d have to assume that “without large earthquakes” means that a small earthquake did occur. We can’t do that, so we eliminate (A).

I hope that helps!

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@GMATNinjaTwo...can you help me by explaining why option E is wrong in Q6. I think the scientists are able to determine where the earth quakes have occurred in the past?

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Question 6

TSBK

@GMATNinjaTwo...can you help me by explaining why option E is wrong in Q6. I think the scientists are able to determine where the earth quakes have occurred in the past?

Question 6 asks us to choose the answer choice that is implied by the author of the passage. So, does the author imply that the researchers in line 18 can tell where earthquakes occurred in the past?

To answer detailed questions like this, go back to that specific portion of the passage to see what the author has said:

Quote:

Researchers initially reported success in identifying these possible precursors, but subsequent analyses of their data proved disheartening. Seismic waves with unusual velocities were recorded before some earthquakes, but while the historical record confirms that most large earthquakes are preceded by minor tremors, these foreshocks indicate nothing about the magnitude of an impending quake and are indistinguishable from other minor tremors that occur without large earthquakes.

Here, there's no discussion about what these researchers knew concerning past earthquakes. The researchers tried to identify precursors to future earthquakes, and the author focuses on how analysis of the researchers' data is "disheartening." He/she then goes on to describe why the data isn't that helpful in predicting earthquakes.

The passage really doesn't discuss at all what these particular researchers knew about the regions where earthquakes happened in the past. Later in the passage, the author implies that some other researchers knew this information, but those are not the researchers that question 6 asks about.

It may seem like a reasonable assumption to say that the researchers knew something about past earthquakes, but that is simply never implied by the author of the passage. So you can eliminate (E) for question 6.

I hope that helps!

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KarishmaB why not choice B in question 6?

Also later in the passage when it talks about 'some researchers' are the researchers being referred to the same as earlier or these are different? And how do you identify that

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6. The author implies which of the following about the ability of the researchers mentioned in line 18 to predict earthquakes?

A. They can identify when an earthquake is likely to occur but not how large it will be.
B. They can identify the regions where earthquakes are likely to occur but not when they will occur.
C. They are unable to determine either the time or the place that earthquakes are likely to occur.
D. They are likely to be more accurate at short-term earthquake prediction than at long-term earthquake prediction.
E. They can determine the regions where earthquakes have occurred in the past but not the regions where they are likely to occur in the future.

Researchers initially reported success in identifying these possible precursors, but subsequent analyses of their data proved disheartening. Seismic waves with unusual velocities were recorded before some earthquakes, but while the historical record confirms that most large earthquakes are preceded by minor tremors, these foreshocks indicate nothing about the magnitude of an impending quake and are indistinguishable from other minor tremors that occur without large earthquakes.

This is all that is given to us about "researchers" mentioned in line 18. What can we say about these researchers? That their methods failed to tell us anything about precursors to earthquakes. The passage doesn't tell us that they could tell the regions where earthquakes would occur. Their methods had failed to give any reliable insight.

Next passage starts with "In the 1980s, some researchers turned their efforts from short-term to long-term..." This is a good 10-15 years after 1971 and we are talking about "some researchers". It is not implied that they are the same researchers (using 'those researchers' etc). Also, it starts from a new paragraph so it's the next thought. Hence, we should ignore anything and everything given in the next paragraph.

So option (C) is correct.

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Hi experts,

I read through the responses on the fourm thoroughly, and unfortunately, my doubts have not been resolved. I would be so appreciative for any clarification on the following...

For "the passage is primarily concerned with", to clarify, Choice C is incorrect because it only mentions challenging the usefulness of dilatancy theory for explaining the occurrence??of precursory phenomena and NOT also challenging Lindh??and Baker's regular earthquake cycle theory whereas Choice D goes against both???

For "according to the passage, laboratory evidence concerning...", Choice C is referring to Lindh and Baker's method, correct? Choice D is incorrect because although I believe that this is referring to Lindh and Baker's method... Lindh and Baker's method only even looked at the San Andreas Fault? Choice E is incorrect because it is only LATER (the next paragraph) that the laboratory evidence is discovered as being unreliable, correct?

For "according to the passage, some researchers based their research..." I see why Choice C is the best answer choice. However, Choice D seems to be a trap answer no? Technically, both Lindh and Baker and the Paleoseismologists discuss long-term earthquakes/that they take place over many years. Do you see what I mean? Choice C does not seem to be saying that this is a matter of regular vs. irregular... just that they occur? Any further clarity on differentiating between these two answer choices would be greatly appreciated.

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For "the passage is primarily concerned with", to clarify, Choice C is incorrect because it only mentions challenging the usefulness of dilatancy theory for explaining the occurrence??of precursory phenomena and NOT also challenging Lindh??and Baker's regular earthquake cycle theory whereas Choice D goes against both???

Basically, yes. The passage does exactly the same thing (a setup/background and a description of the researchers' optimistic views, but then a description of how the theory ultimately failed) twice—first for dilatancy theory and then for Baker and Lindh's theory.

Choice C implies that the part about dilatancy theory is part of the main idea, but that the part about Baker's and Lindh's theory is not. That's absolutely impossible, because the two parts are functionally identical—if one of them is part of the main theme, then so is the other one.

Choice C is also totally wrong for a second reason: it says that the passage challenges (= goes against) the usefulness of dilatancy theory "for explaining the occurrence of precursory phenomena".
That's not true. According to the passage, dilatancy theory SUCCESSFULLY explained/elaborated on the occurrence of (at least some) "precursory phenomena" (= events that occur in the build-up to a big earthquake). The failure point of dilatancy theory was that it couldn't PREDICT EARTHQUAKES.

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06 Sep 2022, 04:27

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woohoo921

For "according to the passage, laboratory evidence concerning...", Choice C is referring to Lindh and Baker's method, correct? Choice D is incorrect because although I believe that this is referring to Lindh and Baker's method... Lindh and Baker's method only even looked at the San Andreas Fault? Choice E is incorrect because it is only LATER (the next paragraph) that the laboratory evidence is discovered as being unreliable, correct?

First things first: Here, all of your questions are about the wrong answers; you aren't asking anything about the correct answer or the path of reasoning that leads to it.
It's possible, of course, that you're not asking about these things because everything about the correct answer is clear to you now. If so, good.
—BUT— The other possibility is that you're just not thinking about the correct answer because you're approaching this problem primarily with process-of-elimination. If that's the case, you're making a mistake. On detail-based questions, you should FIRST see whether you can find what you need in the passage and then AFFIRMATIVELY identify the CORRECT answer. Process-of-elimination is something you should do only if you don't succeed in just going to the passage, finding the relevant information, figuring out what the correct answer SHOULD say/do, and then just going and finding it.

Do you understand how the CORRECT answer works? (Short version: The passage says that the stress stuff may explain "precursory phenomena". To answer the question, you just have to know what "precursory phenomena" are—a definition that you can find at the very beginning of the passage OR that you can actually just figure out from the normal, literal meanings of "precursory" and "phenomena").

Quote:

Choice C is referring to Lindh and Baker's method, correct?

No. Lindh and Baker thought that earthquakes would occur in these areas at REGULAR intervals—i.e., that there would be essentially NO "variation in intervals".

"Variation in intervals" means that the numbers of years between successive earthquakes is IRREGULAR. That turned out to be true—which was precisely the thing that DEFEATED the Baker and Lindh theory.
This "variation" is the thing in the very last paragraph; it was established by "a relatively new field, paleoseismology".

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06 Sep 2022, 04:36

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woohoo921

Choice D is incorrect because although I believe that this is referring to Lindh and Baker's method... Lindh and Baker's method only even looked at the San Andreas Fault?

That's not the problem. At the start of the discussion of Baker and Lindh, the passage notes that they were aware of repeated earthquakes in "certain regions" (plural)—which accords with "various areas".
(The passage describes a study on just the San Andreas, but, that's expected—the researchers and their equipment can only be in one place at a time. Studying one instance of something in order to figure out things that can be generalized to LOTS of instances is exactly how scientific research works—across basically all fields of science. As an analogy, an oncologist studying the development of cancer can only study it in one patient at a time, but observations on one patient with a certain kind of cancer are clearly relevant to the thousands of other patients who have the same kind of cancer.)

In any case, you're overthinking this. Stress patterns in rocks are only mentioned in the first paragraph, so, they are only relevant to the stuff in that paragraph. Baker and Lindh are not mentioned until the third paragraph, so they have nothing at all to do with stress patterns in rocks.
Therefore, D is just irrelevant. If you find yourself stuck doing process-of-elimination, you should at least be able to eliminate D quickly.

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Choice E is incorrect because it is only LATER (the next paragraph) that the laboratory evidence is discovered as being unreliable, correct?

Evidence can't be "unreliable". That doesn't make sense—"Evidence" is FACTUAL data. Data are data are data. Facts are facts. Once something has been established as a fact, it can't be "unreliable".

If you formulate a THEORY that you think will allow you to DO something with that factual evidence—such as to predict earthquakes, here—then that methodology might turn out to be "unreliable" if it doesn't let you do what you're trying to do with it.

In this instance, there are two steps to the prediction process: /1/ Rock stress patterns are used to predict "precursory phenomena", and then /2/ "precursory phenomena" are used to predict earthquakes.

As described in the second paragraph, the problem was step 2. The rock stress data is only related to step 1, so, no, it doesn't help explain the problem.

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06 Sep 2022, 04:52

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woohoo921

For "according to the passage, some researchers based their research..." I see why Choice C is the best answer choice. However, Choice D seems to be a trap answer no?

I don't know what you mean by "trap answer", but the GMAT does not contain ANY answer choices that are misleading or that are worded in 'tricky' ways (i.e., that require you to interpret words in some obscure way that normal people—reading carefully and literally, but otherwise just normally—would not come up with).

If "trap answer" means "it's written to try to trick/deceive you", then, there are a total of zero 'trap answers' in GMAC's entire output of problems.

If "trap answer" just means "contains something that might make somebody choose it", then basically every wrong answer choice on every question would be one! (The alternative would be to write wrong answer choices that are so stupid that nobody would ever pick them, which would make the entire test rather silly as an enterprise.)

About choice D—That choice deals with stress patterns in rocks. That's in the first paragraph, which is only about SHORT-term prediction, so D is irrelevant.

Quote:

Technically, both Lindh and Baker and the Paleoseismologists discuss long-term earthquakes/that they take place over many years. Do you see what I mean?

The adjective "long-term" is only used here for earthquake PREDICTION.

Baker and Lindh were, indeed, trying to find a way to make long-term earthquake predictions.

The paleoseismologists are not concerned with prediction at all (..not as described here, at least). Their deal is looking at geological evidence to figure out when PAST earthquakes happened.

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Choice C does not seem to be saying that this is a matter of regular vs. irregular... just that they occur?

That's exactly what it says. The point is that Baker and Lindh were looking for regular periodic occurrences (because those would let them predict future quakes, at the same intervals), but they didn't know whether, or where, these were actually regular... so they had to do research!

This is what the words literally say:
Noting that earthquakes tend to occur repeatedly in certain regions, Lindh and Baker attempted to identify patterns of recurrence