GEO109_SCI210_Lab 7 Earthquakes SP23
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GEO 109L – Earth, Environment, & Society Lab
SCI 210L – The Dynamic Earth Lab
Lab Exercise 7 – Earthquakes Introduction
In this week’s lab we will continue to investigate the behavior of Earth’s
tectonic plates. Specifically, we will be focusing on how we observe
earthquakes at the surface of the Earth and the effects of significant
quakes on the infrastructure and population. Earthquakes occur as a
result of sudden movement (release of stored energy) along a fault.
Therefore, as long as plates continue to move into, away from, and
alongside each other, earthquakes will keep happening and continue to
pose a risk to the human populations who live near plate boundaries and
other fault systems. Part 1 – Determining the Epicenter of an earthquake
In order to find the surface location, or epicenter, of an earthquake, scientists need to know how long it took for the seismic waves (P and S waves) took to arrive at least three different seismic stations. Once the travel time is known for at least three different stations, they then use the technique known as triangulation to determine the earthquake epicenter. Be sure to review the explanations and videos in the Lab Manual related to Earthquake Triangulation before working on this exercise.
Step 1 – Seismographs and Earthquake Distance
You will use 3 seismographs (from 3 stations across a large area) to determine the epicenter of a major earthquake that occurred on January 12
th
, 2010.
Download the PowerPoint file “Earthquake Seismographs and Time Travel Chart” from the Lab Manual. Complete the worksheet to obtain the distance that the earthquake occurred from each station and record your results below:
Document your work on the PPT slides and include that with your upload to the Assignment Tool.
Lab 7 | 1
NAME: ____________________Table # _____
Station
Location
S-P Interval (minutes)
Distance from Epicenter (km)
1. LEBA
Lebam, WA USA
2. DBIC
Dimbokro, Cote d’Ivoire
3. JSC
Jenkinsville, SC USA
Step 2 – Plot Earthquake Distances and Triangulate
https://www.iris.edu/app/triangulation/
4. Use the Earthquake Triangulation App to plot the circles of Earthquake Distances for each Station. Use the User Event Marker to mark the location where the
epicenter of the earthquake occurred. Include a screenshot of the triangulation below.
Note: Due to estimations used when reading the seismographs, you will likely not have all 3 circles meet at the exact same point. Place your marker in a zone close to where the three circles meet. You can add in layers for Plate Tectonic boundary, change the background, etc to modify your image. Insert a screenshot of your triangulation location in this box – zoom in enough to show the country where this earthquake occurred.
5. Where is this location? (give the country name) – you have most likely heard of this earthquake before.
Part 2 Comparing Two Earthquakes – Same Size, Different Impacts So by now you should know that the earthquake you used in the triangulation exercise occurred in Haiti and is in fact
the January 12
th
, 2010 event that resulted in catastrophic loss of life and destruction of the capital city. In this part of the exercise you will examine this earthquake in more detail and compare it to another recent earthquake of the same magnitude but with very different results.
For each earthquake you will go to the USGS Event Page that contains a layered Interactive Map that can be your main source of information. You can also use the site to link to other information related to the earthquake. Just be careful to not get lost in some of the more technical aspects of the website. In addition there is a map and news video related to each earthquake on the Lab 5 page. Be sure to watch the tutorial video for using the USGS Event page and displaying different layers before working on this part of the lab.
2
Event A: Haiti – January 12, 2010
USGS Event Page: https://earthquake.usgs.gov/earthquakes/eventpage/usp000h60h/executive
6. What type of plate boundary is present near the location? Answer in this column of the table
…
7. What is the magnitude of this Earthquake?
8. Go to the Interactive Map and turn on the Legend Key. a) Using the MMI Contours what was the maximum MMI level near the epicenter? (click on the line closest to the epicenter). b) What is the verbal description for this level (see Resources in Lab)?
9. You can also turn on different Shake Map layers to see various details of the map. (Depending on the event, you might also be able to turn on the DYFI layer). Choose one additional layer to view in the map and describe
the extra/different information it allows you to see. Include a screenshot below.
You can also see separate maps in the Event page.
10. Turn on the Population Density Layer (you might want to turn off the Shakemap but keep the MMI contours on). a) Describe where major populations are located (names of cities – zoom in/out as needed).
b) How do these population centers relate to the earthquake’s location and MMI contours?
Insert here the screenshot of your map with the additional Shake Map layer you chose to describe in #4. Lab 7 | 3
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Event B: Ridgecrest, California - July 5
th
, 2019
USGS Event Page:
https://earthquake.usgs.gov/earthquakes/eventpage/ci38457511/executive
11. What type of plate boundary is present near
the location? Answer in this column of the table
…
12. What is the magnitude of this Earthquake?
13. Go to the Interactive Map and turn on the Legend Key. You may want to adjust the background layer to visualize different aspects. For example “street” view might be easier to read.
a) Using the MMI Contours what was the maximum MMI level near the epicenter? (click on the line closest to the epicenter). b) What is the verbal description for this level (see Resources in Lab)?
14. You can also turn on different Shake Map layers to see various details of the map. (Depending on the event, you might also be able to turn on the DYFI layer). Choose one additional layer to view in the map and describe
the extra/different information it allows you to see. Include a screenshot below.
You can also see separate maps in the Event page.
15. Turn on the Population Density Layer (you might want to turn off the Shakemap but keep the MMI contours on). a) Describe where major populations are located (names of cities – zoom in/out as needed).
b) How do these population centers relate to the earthquake’s location and MMI contours?
Insert here the screenshot of your map with the additional Shake Map layer you chose to describe in #4. Conclusion
16. Write a thoughtful paragraph comparing the similarities and differences between these earthquakes – and of course then their ultimate impacts on the communities. 4