Determine the epicenter of an earthquake from the seismographic data below:
Time of wave arrival
p wave s wave
San Francisco 13:03:21 13:06:04
Dallas 12:04:34 12:05:59
New York City 12:24:54 12:29:50
P wave Speed 5.5 km/sec
S wave Speed 3.5 km/sec
where Z is time Zulu (GMT).
-What City is nearby?
-Is this reasonable?
-Explain why this is reasonable or unreasonable.
Professor was very unclear on instructions.
To determine the epicenter of an earthquake from the given seismographic data, we need to compare the arrival times of the P waves and S waves at different locations.
First, we calculate the time interval between the arrivals of P waves and S waves for each location.
In San Francisco:
Time interval = 13:06:04 - 13:03:21 = 163 seconds
In Dallas:
Time interval = 12:05:59 - 12:04:34 = 85 seconds
In New York City:
Time interval = 12:29:50 - 12:24:54 = 296 seconds
Next, we need to find the distance between each city and the epicenter of the earthquake. We can use the formula distance = speed x time.
For San Francisco:
Distance = 5.5 km/sec x 163 sec = 893.5 km
For Dallas:
Distance = 5.5 km/sec x 85 sec = 467.5 km
For New York City:
Distance = 5.5 km/sec x 296 sec = 1628 km
Now, let's analyze the results:
1. What city is nearby?
Based on the distances calculated, Dallas is the city that is closest to the epicenter of the earthquake.
2. Is this reasonable?
Yes, it is reasonable to assume that Dallas is nearby, given that it has the shortest distance from the epicenter compared to San Francisco and New York City.
3. Explain why this is reasonable or unreasonable.
This is reasonable because seismic waves travel at different speeds through different Earth materials. P waves are faster and arrive first, followed by S waves. By comparing the time intervals between the P waves and S waves at different locations, we can determine the distances from the epicenter. The location with the shortest distance is likely to be closest to the epicenter. In this case, based on the given data, Dallas has the shortest distance, making it a reasonable choice for the city that is nearby the epicenter of the earthquake.