Provide the latitude, longitude, date, depth, magnitude and description for the earthquake identified here via IRIS’s Wilber 3. [3 marks]
Independently validate this event’s epicenter.
From the “Wilber 3: Select Stations” page here, select seismograms for at least three stations that recorded this earthquake.
a. Report the stations used by completing Table 1 below. (Note: “CASY” is a placeholder entry. It should only remain in the table if you intend to make use of it. Marks are awarded here for completing the table and including it in your submission.) [6 marks]
b. Click on the “Show Record Section” to view the seismographs corresponding to the stations you selected.
1 Then adjust the time range so that data is reported
until 1 minute after the S-wave arrival.
2
i. Capture a screenshot (see example below in Figure 1) that includes the
stations you have chosen and their corresponding seismograms. [3
marks]
ii. For each of your stations, determine the P-S wave arrival time difference in minutes and seconds (MM:SS).
3 Add this data to Table 1. [3 marks]
1 Note that not all of the stations you selected may have observed the event of interest. Therefore, ensure you select at least three stations that actually recorded the event.
2 This ensures the S-wave arrival appears in your plot of the records.
3 Note that the arrival time of the S wave (blue vertical bar) is relative to that of the P-wave arrival (red vertical bar at time 0:00:00).
iii. Using travel times curves for P and S waves (Figure 2 below), determine the corresponding distance in kilometers. Add this data to Table 1. (Hint:
Including or referencing a diagram may prove useful.) [3 marks]
iv. State in words the meaning of this distance in kilometers. [2 marks]
c. State in words the meaning of this distance in degrees. (Hint: Including or
referencing a diagram may prove useful.) [2 marks]
Table 1. Details for selected stations and event specifics. (Note: You are expected to provide a
completed version of this table in your submission.)
Access IRIS’s “Earthquake Triangulation” resource.
a. Before opening the resource itself, review the instructions here – especially the
section entitled “IF YOU HAVE SEISMOGRAMS AND WANT TO DETERMINE
THE EARTHQUAKE EPICENTER”.
b. Using the Earthquake Triangulation app here:
i. Estimate the epicenter of the earthquake using the distance data in
kilometers from your Table 1. The epicenter should be identified via the
app using a marker.
Provide a screenshot that illustrates the epicentral location. (The
screenshot should include the triangulated location plus the
marker.) [3 marks]
State the corresponding location of the epicenter in terms of
latitude and longitude. Add this data to Table 2 below. [1 mark]
ii. Estimate the epicenter of the earthquake using the distance data in
degrees from your Table 1. The epicenter should be identified via the app
using a marker.
Provide a screenshot that illustrates the epicentral location. (The
screenshot should include the triangulated location plus the
marker.) [3 marks]
State the corresponding location of the epicenter in terms of
latitude and longitude. Add this data to Table 2 below. [1 mark]
4Note: Stations such as CASY are too far away to allow for distance estimates from travel time graphs!
Station (ID &
Name)
Latitude
(°)
Longitude
(°)
Distance
(°)
P-S wave
difference
(MM:SS)
Distance
(km)
CASY – Casey,
Antartica
-66.28 110.54 105.84 11:45
(11.75)
???
4
c. Using NOAA’s distance calculator here:
i. Determine the accuracy (in kilometers) of the Question 3(b)(i)(2) epicenter
location relative to the official determination stated here in Question 1.
Add this to Table 2 below. [2 marks]
ii. Determine the accuracy (in kilometers) of the Question 3(b)(ii)(2)
epicenter location relative to the official determination stated here in
Question 1. Add this to Table 2 below. [2 marks]
iii. Which of these estimates proves to be more accurate in practice? Why do
you think this is the case? [2 marks]
Table 2. Epicenter determination for the event of interest using length and angular measures for
triangulation. (Note: You are expected to provide a completed version of this table in your
submission.)
Briefly compare the Question 1 event with the 2011 Tōhoku earthquake and tsunami.
State the latitude and longitude of the March 11, 2011 Tohoku earthquake using the
official data available here. [1 mark]
Using NOAA’s distance calculator here, determine the distance between the Tohoku
earthquake and the event identified here in Question 1. [2 marks]
By reviewing the information here, did the earthquake identified in Question 1 pose a
tsunami threat?
5
[1 mark]
40 marks total
Resources
Hyperlinked as needed in context above.
5 As indicated towards the bottom (“All information provided here, including data on latitude, longitude,
depth, magnitude and seismic intensity, is based on initial reports and is subject to change pending
evaluation.”), earthquake specifics detailed on this web page were preliminary – reported some three
minutes after the event. This explains why there exists some differences relative to the official
determination identified in Question 1.
Distance Estimation Latitude (°) Longitude (°) Accuracy (km)
Kilometers
Degrees
Note: Figures follow below.
Figure 1. A “Show Record Section” screenshot obtained after selecting three events using the
“Wilber 3: Select Stations” page here.
Figure 2. Travel time curves for P and S waves.
Sample Solution
