Guiding Question: How can you locate an earthquake's epicenter?
Hypothesis: I think that to find the epicenter of an earthquake, you need to find the center of all three cities that felt the earthquake, and in the middle, you will find the epicenter of the original earthquake.
Questions for Reflection:
1.) Observe the three circles you have drawn. Where is the earthquake's epicenter?
According to my map, the epicenter of the earthquake in question is located in the south of Tennessee, in between the cities of Memphis and Chattanooga.
2.) Which city on the map is closest to the earthquake's epicenter? How far, in kilometers, is this city from the epicenter?
The city closest to the epicenter is in Chicago, Illinois, and it is approximately 730 kilometers away from it.
3.) In which of the three cities listed in the data table would seismographs detect the earthquake first? Last?
Of the three cities on the map, Chicago would detect the earthquake first, because it is closest to it. The waves would hit Illinois first, and then the seismographs would detect it and record it. The last city to get word of the earthquake would be Denver, Colorado, because it is farthest away from the epicenter. The waves would have a longer distance to travel, and so the seismographs would record them much later than the other two cities.
4.) About how far from San Francisco is the epicenter that you found? What would be the difference in arrival times of the P waves and S waves for a recording station in San Francisco?
The epicenter I found is about 3,300 km away from San Francisco. The P waves would arrive much sooner than the S waves, because P waves travel in longitudinal waves, which travel much more quickly than S (transverse) waves.
5.) What is the earthquake risk in this area, and why might this earthquake occurred?
According to my plate map, I can assume that there is a medium risk of earthquakes in Tennessee. This is because it isn't that close to any plate boundaries, but it isn't exactly far from them either. The earthquake in question could have been caused by either the North American Plate and the Nazca Plate pushing together under compression stress, or the North American and African Plates pulling apart through tension. I am more convinced that this earthquake was caused by compression, because:
a.) Many more major earthquakes are caused by compression.
b.) The area of compression is slightly closer to Tennessee than the area of tension.
6.) What happens to the difference in arrival times between P waves and S waves as the distance from the earthquake increases?
As the distance between earthquake epicenter and city increases, the difference between the arrival time of P waves and S waves broadens. This is because the P waves are continually traveling more quickly than S waves, and when there is more time to pull ahead, there will be a greater difference between the two waves' arrival.
Overall Reflection:
All in all, my hypothesis was incorrect. I thought that to find the epicenter of an earthquake you would need to find the place in between all the cities that felt it. Instead, you need to use a compass to draw circles around the three cities and look for where the lines cross. That will be where the epicenter is.
Hypothesis: I think that to find the epicenter of an earthquake, you need to find the center of all three cities that felt the earthquake, and in the middle, you will find the epicenter of the original earthquake.
Questions for Reflection:
1.) Observe the three circles you have drawn. Where is the earthquake's epicenter?
According to my map, the epicenter of the earthquake in question is located in the south of Tennessee, in between the cities of Memphis and Chattanooga.
2.) Which city on the map is closest to the earthquake's epicenter? How far, in kilometers, is this city from the epicenter?
The city closest to the epicenter is in Chicago, Illinois, and it is approximately 730 kilometers away from it.
3.) In which of the three cities listed in the data table would seismographs detect the earthquake first? Last?
Of the three cities on the map, Chicago would detect the earthquake first, because it is closest to it. The waves would hit Illinois first, and then the seismographs would detect it and record it. The last city to get word of the earthquake would be Denver, Colorado, because it is farthest away from the epicenter. The waves would have a longer distance to travel, and so the seismographs would record them much later than the other two cities.
4.) About how far from San Francisco is the epicenter that you found? What would be the difference in arrival times of the P waves and S waves for a recording station in San Francisco?
The epicenter I found is about 3,300 km away from San Francisco. The P waves would arrive much sooner than the S waves, because P waves travel in longitudinal waves, which travel much more quickly than S (transverse) waves.
5.) What is the earthquake risk in this area, and why might this earthquake occurred?
According to my plate map, I can assume that there is a medium risk of earthquakes in Tennessee. This is because it isn't that close to any plate boundaries, but it isn't exactly far from them either. The earthquake in question could have been caused by either the North American Plate and the Nazca Plate pushing together under compression stress, or the North American and African Plates pulling apart through tension. I am more convinced that this earthquake was caused by compression, because:
a.) Many more major earthquakes are caused by compression.
b.) The area of compression is slightly closer to Tennessee than the area of tension.
6.) What happens to the difference in arrival times between P waves and S waves as the distance from the earthquake increases?
As the distance between earthquake epicenter and city increases, the difference between the arrival time of P waves and S waves broadens. This is because the P waves are continually traveling more quickly than S waves, and when there is more time to pull ahead, there will be a greater difference between the two waves' arrival.
Overall Reflection:
All in all, my hypothesis was incorrect. I thought that to find the epicenter of an earthquake you would need to find the place in between all the cities that felt it. Instead, you need to use a compass to draw circles around the three cities and look for where the lines cross. That will be where the epicenter is.
Excellent analysis. You used your knowledge about travel time between P waves and S waves and the map to discuss distances from the epicenter. Well done!
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