NAME DATE PARTNER(S) SHAKE, RATTLE, AND ROLL INVESTIGATING EARTHQUAKES The city of San Francisco was destroyed by a 7.8 magnitude earthquake that ruptured gas lines and set the city ablaze. March 28, 1964 marked the occurrence of a magnitude 9.2 earthquake that destroyed Anchorage, Alaska. On December 26, 2004, a magnitude 9.0 earthquake in the Indian Ocean near Sumatra spawned a devastating tsunami. A magnitude 7.0 earthquake struck the capital of Haiti, Port-au-Prince, on January 12, 2010 causing massive damage and extreme loss of life. Concepcion, Chile was severely shaken by an 8.8 magnitude temblor on February 27, 2010. The coastal regions of California and Alaska are constantly shaken by minor quakes. What happens within the Earth when an earthquake occurs? How do scientists know where the quake is located and how strong it is? Let s find out! Activity 1 Making Waves Dynamic processes occurring within the Earth send waves through rock layers. To simulate these waves we will use a Slinky. 1. Locate an open section of floor (in the classroom or hallway) where you can stretch the Slinky to at least 1 meter (about 3 feet). Have members of your group hold the ends of the Slinky stretched out about 1 meter. Holding the Slinky on the floor have one person pulse (quickly push) the Slinky toward the other person. Watch the motion of the sections of coil. Repeat several times. What is happening to the distance between the parts of the coil? Explorations in Earth and Space Science PSC 1210 Prince George s Community College 81
The motion causes the compression and dilation of parts of the Slinky along a horizontal axis. When this occurs on Earth it is referred to as a primary wave or a P- wave. This is one motion that occurs when an earthquake strikes. 2. Holding the Slinky slightly above the floor, have one person quickly shake the Slinky up and down. Repeat several times. Describe (or sketch) the results here. How does the Slinky move with respect to the floor? This type of wave is called a secondary wave, a shear wave, or an S-wave. It moves material in a vertical direction. 3. Are there any other motions you can generate with the Slinky? Describe them below. STOP FOR THE POWERPOINT PRESENTATION ON EARTHQUAKES. The rest of this lab will be conducted in the computer lab. When you get to the lab launch Internet Explorer and go to: academic.pgcc.edu/~bgage/earthquake.htm. When you open the website, the links will be active and you can click on them as you work. Activity 2: Analyzing a Seismogram In this activity you will work individually or in pairs to: select an earthquake location; determine the S-P interval for seismographs from three stations to determine the distance to the epicenter of a quake; determine the magnitude of an S-wave and use it and the distance to estimate the magnitude of the quake. You will be using software that is located at: http://www.sciencecourseware.com/virtualearthquake/ 1. Start with the button labeled Execute VirtualEarthquake at the bottom of the page. 2. The material on the next screens will be a reinforcement of the content of the PowerPoint presentation. Read these as you proceed through the activity. Print each page of the activity as you complete it before proceeding. Attach these pages to the end of this activity. 82 Explorations in Earth and Space Science PSC 1210 Prince George s Community College
DID YOU EARN A CERTIFICATE? If you want a more challenging activity to analyze an earthquake in your spare time try: http://www.sciencecourseware.com/eec/earthquake/ If you want to play with measuring S-P intervals and determining distances, you can open and work with a specially designed Excelet (interactive Excel file) on earthquakes by clicking here. Activity 3: Where do Earthquakes Occur? In the first three months of 2010, ten earthquakes with magnitudes from 5.9 to 8.8 occurred on three different continents. While this time period has been particularly active, earthquakes occur every day in multiple locations. Do you think the distribution of earthquakes is random or is there a pattern to seismic activity? Why do you think so? What causes these earthquakes? There are thousands of seismic stations positioned all over the globe that constantly record earth tremors. Let s look at the world-wide location of earthquakes. 1. Go to http://earthquake.usgs.gov/eqcenter/recenteqsww/. This page displays the earthquakes that have been registered around the world in the last 7 days. Are the quakes scattered or do they occur in specific regions? What regions have been most active in the last week? Outline these regions in green on the World Map at the end of this activity. Are there any continents where there is no seismic activity? Explorations in Earth and Space Science PSC 1210 Prince George s Community College 83
2. Now go to the left side of the screen and under PAST and click on Past 8-30 Days. The map now shows the earthquakes that have been registered in the last month. Do you see the same distribution of earthquakes or are there significant differences? Explain. 3. Now let s display global seismicity (world-wide earthquake activity) in a different way using Google Earth. Go to earth.google.com. Click on the download button and follow instructions to install Google Earth. 4. Go to http://earthquake.usgs.gov/earthquakes/catalogs/. Click on M 1+ earthquakes, past 7 days (colored by age). Google Earth should come up with recent earthquakes displayed. Identify and describe 4 different locations where there has been significant seismic activity in the past week. Color these areas in yellow on the World map at the end of this activity. 5. Close Google Earth. When you see the following message, select SAVE. 84 Explorations in Earth and Space Science PSC 1210 Prince George s Community College
6. To look at earthquakes since 1900 we will open another file to display in Google Earth. Go back to the Activity Earthquake page and click on Historic Earthquakes for Goggle Earth. When you get the next message select Open. Google Earth will display. In the upper left corner there will be a slider. Be sure that Asia or North/South America is rotated to face you. Move the slider to display the earthquakes since 1900. Rotate the Earth to look at the locations of earthquakes. What regions show significant activity that you did not list in #4? Describe the locations here and outline the regions in blue on the World map. Is there still a pattern to the location of the earthquakes or are they scattered all over the globe? Close Google Earth as before, saving the items to My Places. 7. While we have Google Earth on the computer, let s look at the distribution of volcanoes. Click here to load a Google Earth file on world volcanoes. Open the file. Google Earth will come up with the earthquakes displayed in red. Outline the regions that show volcanic activity on the World Map in RED. Do any of the regions of volcanism coincide with areas of seismic activity? If so, where? Are there regions of the Earth where there is volcanism but little or no seismic activity? If so, where? Explorations in Earth and Space Science PSC 1210 Prince George s Community College 85
8. One feature of Google Earth is that if you have saved information sets in My Places, you can display them simultaneously. Go to the left of the Google Earth screen under PLACES and check the box for Major Earthquakes, 1900. Move the slider forward and back to display the earthquakes. Move the slider to change the number of earthquakes displayed for different segments of the Earth. This may help modify the answer to the last part of question 7. 86 Explorations in Earth and Space Science PSC 1210 Prince George s Community College
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