Which of the following statements correctly describes how earthquakes are measured and the possible maximum size they can reach?

• A. Earthquakes are measured using a thermometer, and the largest possible earthquake is $10$ on the Richter scale.
• B. Earthquakes are measured by the number of aftershocks, and the maximum size is determined by the depth of the earthquake.
• C. Earthquakes are measured by the amount of ground shaking felt by people, and there is no upper limit to how large an earthquake can be.
• D. Earthquakes are measured using the Richter scale, which assigns a magnitude based on the amplitude of seismic waves, and the largest recorded earthquake had a magnitude of about $9.5$.

Answer: (D)

Verified step by step guidance

1. Understand that earthquakes are measured using the Richter scale, which quantifies the magnitude based on the amplitude of seismic waves recorded by seismographs.
2. Recall that the Richter scale is logarithmic, meaning each whole number increase represents a tenfold increase in measured amplitude and roughly 31.6 times more energy release.
3. Recognize that the Richter scale does not have a fixed upper limit theoretically, but the largest recorded earthquake had a magnitude of about 9.5.
4. Note that measuring earthquakes by the number of aftershocks or by how much shaking people feel is not the standard scientific method for determining magnitude.
5. Conclude that the correct description involves the Richter scale measurement and the known maximum recorded magnitude, rather than arbitrary limits or other measurement methods.