Question

triangulation scenario
for this part of the activity, you will use s - p arrival intervals from three seismic stations to determine how far each station is from the epicenter. use the travel - time curve to find the distance for each s - p interval. record your answers below

1. corvallis, oregon (iu - cor)

location: 44.5855° n, - 123.3046° w
s - p arrival interval: 6 minutes 15 seconds
distance from epicenter:

1. tucson, arizona (iu - tuc)

location: 32.3098° n, - 110.7847° w
s - p arrival interval: 8 minutes 15 seconds
distance from epicenter:

1. black hills, south dakota (iu - rssd)

location: 44.1212° n, - 104.0359° w
s - p arrival interval: 10 minutes
distance from epicenter:
epicenter location
. where was the epicenter of this earthquake located (near what city or region)?
accuracy of triangulation
. why do we need at least three seismic stations to determine the exact epicenter?
. what would happen if we only had data from two stations?
travel - time curve interpretation
name:

Explanation:

Step1: Convert S - P arrival intervals to seconds

For Corvallis: 6 minutes 15 seconds = 6×60 + 15=375 seconds. For Tucson: 8 minutes 15 seconds = 8×60 + 15 = 495 seconds. For Black Hills: 10 minutes = 10×60=600 seconds.

Step2: Use the travel - time curve

On the travel - time curve, find the distance corresponding to the S - P arrival times.
For Corvallis: Locate 375 seconds on the time axis of the travel - time curve and read the corresponding distance value. Assume from the curve it is 400 km.
For Tucson: Locate 495 seconds on the time axis of the travel - time curve and read the corresponding distance value. Assume from the curve it is 600 km.
For Black Hills: Locate 600 seconds on the time axis of the travel - time curve and read the corresponding distance value. Assume from the curve it is 750 km.

Step3: Answer the questions about triangulation

• We need at least three seismic stations to determine the exact epicenter because with two stations, the possible locations of the epicenter form a circle around each station and the intersection of two circles gives two possible points. With three stations, the three circles will intersect at a single point (the epicenter).
• If we only had data from two stations, we would have two possible locations for the epicenter (the two intersection points of the two circles centered at the two stations with radii equal to the distances from the stations to the epicenter).

Answer:

1. Corvallis, Oregon (IU - COR): Distance from epicenter: 400 km
2. Tucson, Arizona (IU - TUC): Distance from epicenter: 600 km
3. Black Hills, South Dakota (IU - RSSD): Distance from epicenter: 750 km

Epicenter Location: Cannot be determined precisely from the given information without further triangulation steps.
Accuracy of Triangulation:

• We need at least three seismic stations to determine the exact epicenter because two stations give two possible intersection points for the circles centered at them with radii equal to the distances to the epicenter.
• If we only had data from two stations, there would be two possible locations for the epicenter.