Final answer:
The greater intensity rating for an earthquake if it hit near New York City according to the Modified Mercalli scale is likely due to the proximity of the earthquake's epicenter, resulting in stronger seismic wave amplitude close to the source. Option c is the correct answer.
Step-by-step explanation:
The question asks why an earthquake of the same magnitude would have a greater intensity rating on the Modified Mercalli scale if it hit 20 miles outside of New York City. To understand this, we need to look at the factors that affect the intensity of an earthquake. One critical aspect is the distance from the epicenter. The closer a location is to the earthquake's epicenter, the more intense the shaking is likely to be. This is because earthquake waves are stronger and have higher amplitudes closer to the epicenter, and their amplitude decreases as they spread out over a larger area. However, the Modified Mercalli scale does not only consider seismological measurements but also the effects on structures and people.
Another important factor is the local geology and soil conditions. Areas with soft soil, like sediment-filled valleys, will experience more intense shaking than areas with solid rock, due to the soil amplifying the seismic waves. Furthermore, the design and construction standards in New York City may contribute to a perception of increased intensity. Buildings and infrastructure that are not designed to withstand seismic activity may suffer more damage, thus raising the Modified Mercalli intensity rating.
Given these points, when considering the provided options, we can determine that the correct option is C) The earthquake's epicenter is closer to New York City. Structures and areas closer to the epicenter will likely experience more severe shaking due to the proximity to the source of the earthquake waves.