By George Yan (9 Grade)
Purpose
The purpose of this lab is to use seismograms to determine the location of an earthquake’s epicenter.
Seismogram Graph
First we determined the time interval on the seismograms is 10 seconds.
Second, we added data into the below table:
Analysis from the Seismic Data Table
In comparison to Chicago, Wink is closer to from the epicenter. Because the difference between the travel time is shorter, which leads to an earlier origin time.
Arrival times were different, and origin time should have been same for all location. The reason why the origin time should be the same is because the origin time is the exact time the earth quake occurred, and not when it reached somewhere else.
One reason why the origin times may not be the same could be humanmeasurement error during the lab. We used a physical pencil and paper to find the epicenter distance and the travel time which may be off, as you cannot mark a pencil mark and line up perfectly.
Epicenter Map Method
We were also given the following map to locate epicenter.
First we determined the interval is in 100km for the scale on the US map above.
Steps
- Use the scale of distance on the map to set the compass to the correct radius.
- Construct a circle for assigned city.
- Mark with an X, the epicenter of the earthquake.
Conclusion
The epicenter is to the west of Denver by between 100 to 200 kilometers. Its also north of Wink. The seismic station closes to the epicenter was Wink. One piece of qualitative evidence is that it’s circle is smaller than the other stations. Quantitative evidence from Data table includes the P wave travel time being the shortest and the epicenter distance being also the shortest.
The reason people living in San Francisco would experience the larger earthquake is because San Francisco is much closer to a fault line, which is a major cause of earthquakes.
