The distance to an earthquake requires knowing two things. One piece of information consists of measuring
[ Select ]
the difference in the arrival times of the P and S waves
the ratio of the amplitude of the largest P and S waves
the arrival time of surface waves
the speed of surface waves
. One other key piece of information that you need to know is
[ Select ]
the speed of the surface waves
the amplitude of the S waves
the speeds of the P and S waves
the locations of three seismometers
.

Question

The distance to an earthquake requires knowing two things.  One piece of information consists of measuring 
[ Select ]
the difference in the arrival times of the P and S waves
the ratio of the amplitude of the largest P and S waves
the arrival time of surface waves
the speed of surface waves
 .  One other key piece of information that you need to know is 
[ Select ]
the speed of the surface waves
the amplitude of the S waves
the speeds of the P and S waves
the locations of three seismometers
 .

BlackTom AI · Accepted Answer

Question restatement: The distance to an earthquake requires knowing two things. One piece of information consists of measuring [ Select ] the difference in the arrival times of the P and S waves, the ratio of the amplitude of the largest P and S waves, the arrival time of surface waves, the speed of surface waves. One other key piece of information that you need to know is [ Select ] the speed of the surface waves, the amplitude of the S waves, the speeds of the P and S waves, the locations of three seismometers.

Option analysis for the first dropdown:
- the difference in the arrival times of the P and S waves: This is the classic method used in seismology to determine distance to an earthquake. The P-wave and S-wave travel at different speeds; by measuring how much later the S-wave arrives compared to the P-wave at a seismometer, you can calculate the distance to the earthquake, given knowledge of the P and S wave speeds. This option aligns with the standard equation distance ∝ (arrival_time_S − arrival_time_P) when P and S speeds are known.
- the ratio of the amplitude of the largest P and S waves: Amplitude ratios do not provide a reliable distance measure because amplitudes are affected by focal mechanisms, path effects, attenuation, and site amplification. This makes it an unreliable or incorrect method for determining distance.
- the arrival time of surface waves: While surface waves provide information about the event, the arrival time of surface waves alone does not yield a straightforward distance measure without additional constraints or velocities; it is not the standard primary method for distance estimation.
- the speed of surface waves: Knowing surface wave speed helps with certain interpretations, but by itself it does not give distance to the earthquake without timing information and other velocity models. This is not the primary quantity used for distance calculation in the classic two-quantity approach.

Option analysis for the second dropdown:
- the speed of the surface waves: Surface wave speed is helpful for certain analyses, but the standard dual-information approach for distance relies on the relative speeds of P and S waves, not primarily on surface wave speed alone. Therefore this is not the key second piece in the typical distance calculation.
- the amplitude of the S waves: Amplitude data are influenced by path effects and focal mechanisms; amplitude alone does not determine the distance or the velocity relationship necessary for distance estimation.
- the speeds of the P and S waves: Correct. The essential second piece of information is the velocities of P and S waves, which, together with the measured time difference between P and S arrivals, allow the calculation of distance using the difference in arrival times and the known velocity contrast between P and S waves.
- the locations of three seismometers: While Having multiple seismometers improves localization of the epicenter, the fundamental distance calculation from a single station uses the travel-time difference and the P- and S-wave speeds; three-seismometer geometry is not the core two-piece information for distance per se.

In summary, the first blank should be filled with the information that directly links arrival times to distance via the P- and S-wave timing difference, while the second blank should be filled with the wave speeds that enable the conversion from a time difference to a distance measurement. The combination of (a) the difference in arrival times of P and S waves, and (b) the speeds of the P and S waves, provides the standard method for determining an earthquake’s distance from the recording station.

类似问题

Which of the following statements concerning the behavior of seismic waves within the Earth is FALSE?

Which type of seismic wave does NOT travel through liquids (such at the liquid outer core of the earth)?

Which of the following statements is FALSE?

Seismic waves are generated from what natural phenomenon?

What changes, if any, will occur as seismic waves pass from the Earth’s lower mantle UP into the OVERLYING layer?

Which of the following are true about both P- and S- waves? (there are 2 correct answers)

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