Passage 1

In 1971, researchers aimed to predict earthquakes by identifying short-term precursors like changes in seismic wave velocity. Dilatancy theory, based on lab observations, explained this: under stress, rocks first contract, then crack and expand, allowing groundwater in and weakening the rock. This process could cause seismic velocity changes and increased small tremors before quakes. Initial studies showed promise, suggesting identifiable precursors. However, later analysis proved disappointing. While unusual seismic waves were observed before some quakes, and most large earthquakes are preceded by minor tremors, these foreshocks are indistinguishable from regular tremors and reveal nothing about quake magnitude. The episode underscores the difficulty of using complex natural patterns to predict catastrophic events with precision, despite sound theoretical foundations.

Which one of the following statements best reflects the central idea of the above passage?

(a)The dilatancy theory, despite its initial promise based on laboratory findings, proved entirely incorrect in explaining seismic phenomena.

(b)Earthquake prediction based on identifying short-term precursors is an inherently flawed approach due to the complexity of geological processes.

(c)Prediction of earthquakes using the dilatancy theory to interpret precursors showed initial promise but ultimately highlighted challenges in precision.

(d)The most significant outcome of the 1971 earthquake prediction research was the discovery that foreshocks are indistinguishable from regular tremors.

Question

Passage 1

In 1971, researchers aimed to predict earthquakes by identifying short-term precursors like changes in seismic wave velocity. Dilatancy theory, based on lab observations, explained this: under stress, rocks first contract, then crack and expand, allowing groundwater in and weakening the rock. This process could cause seismic velocity changes and increased small tremors before quakes. Initial studies showed promise, suggesting identifiable precursors. However, later analysis proved disappointing. While unusual seismic waves were observed before some quakes, and most large earthquakes are preceded by minor tremors, these foreshocks are indistinguishable from regular tremors and reveal nothing about quake magnitude. The episode underscores the difficulty of using complex natural patterns to predict catastrophic events with precision, despite sound theoretical foundations.
 

Which one of the following statements best reflects the central idea of the above passage?

(a)The dilatancy theory, despite its initial promise based on laboratory findings, proved entirely incorrect in explaining seismic phenomena.

(b)Earthquake prediction based on identifying short-term precursors is an inherently flawed approach due to the complexity of geological processes. 

(c)Prediction of earthquakes using the dilatancy theory to interpret precursors showed initial promise but ultimately highlighted challenges in precision. 

(d)The most significant outcome of the 1971 earthquake prediction research was the discovery that foreshocks are indistinguishable from regular tremors.

ONLiNE UPSC · Accepted Answer

Statement (a) is not correct: The passage says dilatancy theory could explain certain precursors and was a "sound theoretical foundation." The disappointment was in its application for precise prediction, not necessarily that the theory itself was entirely incorrect in describing rock behavior under stress.

Statement (b) is not correct: The passage describes one "episode" and its disappointing outcome for precise prediction. It underscores the difficulty but doesn't conclude the entire approach of studying precursors is "inherently flawed" for all purposes, or that no progress can ever be made.

Statement (c) is correct: This statement accurately captures the narrative: the initial aim (prediction via precursors in 1971), the theoretical basis (dilatancy), the initial hope ("showed promise"), the eventual outcome ("disappointing" for precision), and the broader lesson learned (difficulty of precise prediction in complex natural systems).

Statement (d) is not correct: While the indistinguishability of foreshocks was a key finding contributing to the disappointment, the central idea is broader, encompassing the entire research episode, its theoretical basis, its initial promise, and the ultimate lesson about prediction difficulties, not just this single outcome.

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