Question

Residents in Port-au-Prince complained of extreme shaking during the earthquake, while residents of Santo Domingo, the capital of the Dominican Republic that sits 150 miles east of Port-au-Prince, assumed the shaking was caused by the passing of a large truck. Based on the Modified Mercalli Intensity Scale, the residents of Port-au-Prince mostly like experienced an intensity of ___, while the residents of Santo Domingo experienced an intensity of ___. a. VII, II b. VIII, III c. X, III d. X, IV

Short answer

Option b. VIII, III is correct.

Step-by-step solution

Understand the Modified Mercalli Intensity Scale

The Modified Mercalli Intensity (MMI) Scale measures the intensity of shaking during an earthquake, ranging from I (not felt) to XII (total destruction). Lower numbers indicate minor shaking, while higher numbers indicate more severe impacts.

Analyze the Description of Shaking in Port-au-Prince

Residents in Port-au-Prince reported extreme shaking, which indicates a higher intensity on the MMI Scale, potentially around levels VII, VIII, or above. Levels VII and VIII describe damage to buildings and difficulty in standing.

Analyze the Description of Shaking in Santo Domingo

The residents of Santo Domingo felt a milder shaking that they mistook for a passing truck. This suggests a lower intensity on the MMI Scale, likely around II to IV. Level II is where shaking is felt by a few people, and Level III is where it may be felt indoors.

Match the Observations to the Intensity Levels

Using the descriptions, residents of Port-au-Prince likely experienced an intensity of VIII (severe), and those in Santo Domingo an intensity of III (weak). These correspond to higher impacts in Port-au-Prince and a mild perception in Santo Domingo.

Choose the Correct Option

Among the given options, b. VIII, III matches our analysis of the experienced intensities in Port-au-Prince and Santo Domingo based on the descriptions and the MMI Scale.

Key concepts

earthquake intensity

Earthquake intensity is an important concept to understand when analyzing the effects of seismic activity on different locations. Unlike earthquake magnitude, which measures the energy released at the source of the earthquake, intensity measures how strongly the earthquake is felt at different locations. This is crucial for assessing damage and the impact on human infrastructure and daily life.
The Modified Mercalli Intensity (MMI) Scale is commonly used to determine earthquake intensity. It categorizes the effects of an earthquake from I, where it is not felt, up to XII, which means total destruction. Lower levels on this scale typically involve minor movement only noticed by few people. In contrast, higher levels indicate noticeable shaking, possible structural damage, and significant disruptions. When residents in different regions experienced varying levels of shaking, graders use the MMI to describe their experiences quantitatively. For example, someone feeling slight tremors might be categorized into level II or III, while report of severe shaking might require levels VII or higher.

Port-au-Prince earthquake

The Port-au-Prince earthquake was a powerful seismic event that had a profound impact on Haiti's capital and its residents. Located near fault lines, the area is prone to seismic activity, and the earthquake highlighted the vulnerabilities of its infrastructure.
Residents described the incident in extreme terms, with intense shaking strong enough to damage buildings and make standing difficult. This description aligns with higher intensities on the Modified Mercalli Intensity Scale, likely placing the experience around level VIII. Such a classification indicates severe structural damage and life-threatening conditions across affected areas.
Understanding the degree of shaking in Port-au-Prince is crucial for disaster response and future preparedness. It assists in recognizing the urgent need for stricter building codes and better urban planning to withstand potential seismic events, aiming to mitigate the intense human and economic costs seen in disasters like this.

seismic analysis

Seismic analysis plays a vital role in understanding the dynamics of earthquakes and how they impact different regions. It involves studying the recorded intensities, geological formations, and structural responses to an earthquake.
By analyzing seismic data, experts can estimate the distribution of intensity levels across various locations. In the case of the Port-au-Prince earthquake, detailed seismic analysis would involve examining the intensity scale readings reported in the areas such as Port-au-Prince and Santo Domingo.
These analyses help in determining the areas most affected by an earthquake, allowing emergency services to allocate resources efficiently. Additionally, it supports long-term planning and development by highlighting regions that may require stronger constructions or reinforcement to endure future seismic events.

Santo Domingo shaking

In contrast to the intense experiences in Port-au-Prince, residents in Santo Domingo, located 150 miles to the east, reported much milder tremors. The shaking was so subtle that some believed it to be the passing of a large truck.
Using the Modified Mercalli Intensity Scale, such an experience is likely categorized around level III, indicating a gentle shaking felt indoors but unlikely to cause structural damage. This difference in intensity highlights how distance and geological conditions can influence the perception and impact of an earthquake.
Understanding differences in shaking experiences, like those between Santo Domingo and Port-au-Prince, is essential for regional planning and emergency response. It reveals the varying levels of vulnerability and helps frame appropriate measures for earthquake preparedness tailored to specific local conditions.