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Difficulty: MediumExplicit Detail Retrieval

In 1905, geologist Richard Dixon Oldham analyzed seismic waves generated by the 1897 Assam earthquake to investigate Earth's internal structure. By comparing the arrival times of primary (P) and secondary (S) waves at recording stations globally, Oldham identified a distinct shadow zone beyond 104 degrees from the epicenter where direct S-waves failed to emerge. From this specific absence, Oldham deduced the existence of a central fluid core that impeded shear wave transmission. However, because his instruments lacked the sensitivity to detect faint, refracted P-waves passing through the deepest interior, Oldham incorrectly estimated the core's radius to be substantially larger than modern measurements indicate, attributing the wave attenuation entirely to homogenous core density rather than a distinct solid inner core boundary.

Based on the passage, which of the following statements regarding Richard Dixon Oldham's 1905 seismic investigation are explicitly supported? Consider each of the three choices separately and select all that apply.

  1. Oldham's deduction of a fluid central core relied on observing the absence of direct S-waves at stations located more than 104 degrees from the earthquake's epicenter.Answer
  2. B
    Oldham correctly calculated the precise radius of the Earth's core by measuring the speed of refracted P-waves.
  3. The seismological recording instruments available to Oldham failed to register faint P-waves passing through the planet's deepest interior.Answer

Answer

The supported statements are that Oldham's deduction of a fluid central core relied on observing the absence of direct S-waves beyond 104 degrees from the epicenter, and that the seismological recording instruments available to Oldham failed to register faint P-waves passing through the planet's deepest interior.
The passage explicitly supports two statements. First, it confirms that Oldham deduced a central fluid core from the absence of direct S-waves at stations beyond 104 degrees from the epicenter. Second, it explicitly mentions that Oldham's instruments lacked the sensitivity required to detect faint P-waves passing through the deepest interior of the Earth.

Step-by-Step Solution

1
Locate explicit details regarding Oldham's deduction of the fluid core and the 104-degree boundary.
The passage states that direct S-waves failed to emerge beyond 104 degrees and 'from this specific absence, Oldham deduced the existence of a central fluid core.' This confirms the statement regarding his core deduction.
Explicit detail retrieval requires matching passage facts directly to the option claims.
2
Evaluate the option regarding the calculation of the core radius and P-wave measurement.
The text states Oldham 'incorrectly estimated the core's radius' and that his instruments 'lacked the sensitivity to detect faint, refracted P-waves.' This directly refutes the claim of a correct calculation.
Identify direct factual contradictions in detail retrieval distractors.
3
Evaluate the option regarding instrument sensitivity and deep interior P-waves.
The text explicitly states 'because his instruments lacked the sensitivity to detect faint, refracted P-waves passing through the deepest interior,' directly supporting this claim.
Confirm explicit phrasing paraphrases without making unwarranted leaps.

Key Concept

Explicit Detail Retrieval
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Explicit Detail Retrieval

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