Department of Earth Science |Northeastern Illinois University

INTRODUCTION TO EARTH SCIENCE
ESCI 121
Section 05
 Spring 2009

Daily Objectives #21 (April 9, 2009)                                                                                                           Dr. Sanders

HOMEWORK REMINDERS
 n   Don't forget to sign up for the assignment on Weather Tracking, posted on the Homework page.
 n   An extra credit homework opportunity is posted on the homework page as well.  If you wish to earn extra credit by completing this assignment, you must turn it in by April 14.


TOPOGRAPHIC MAPS

 n Define:    ○ topography           ○ topographic map           ○ contour line

 n Using the green globs of "playdough", sculpt a model of the hill outside the Science Building. 

n Scribe contour lines into your sculpture.

n Based on your model, sketch a topographic map of the area.

 
MEASURING EARTHQUAKES
 

Today's Challenge:  Find and analyze seismograms for the magnitude 6.3 earthquake in Central Italy Monday, April 06, 2009 at 01:32:39 UTC.  (What is UTC?)
Follow the three steps below.
First:  Use the "Rapid Earthquake Viewer". 

Go to http://rev.seis.sc.edu/ .  (If you want a tutorial, scroll down; you'll find it under "Educational Links of Interest", on the DLESE Teaching Boxes page.)  Click "Earthquake View", and on the map, select the Central Italy earthquake of April 6, 2009.  Be sure to choose the one with a magnitude of 6.3 !!

Next, you'll see seismograms for 10-12 monitoring stations.  Click the different options under "Seismograph Orientation" to see what happens to the seismograms.

Go to the class wiki and log in.  On the Rapid Earthquake Viewer page, choose one of the monitoring stations; the station name appears below the seismograms.  On the wiki page, sign up for your choice.

Scroll to the list of station codes and click yours.  You will see three seismograms from that station.  (What is the difference between them?)  Click "Overlay estimated P wave/S wave arrival times".  You may want to "Select Zoom" to zoom closer to either the P wave or S wave.

Determine the exact P-S time lag (time difference).  Fill in all the values in the table on the wiki page. 
 
Second:  Use the IRIS BUD page.

Open this page: http://www.iris.edu/bud_stuff/bud/bud_start.pl?BUDDIR=/budnas/virtualnets/ALL
A help page is available at  http://www.iris.edu/bud_stuff/dmc/help.htm . 
For more help on picking out P and S waves, see "How Do I Read a Seismogram?"

Under "network", select the first two letters of your station code (from the REV page).  Scroll to the bottom, choose "Select Date", and click on April 6, the date of the Central Italy earthquake. 

A list of stations will come up.  Find your station, and look for three codes in a row that end in E, N, and Z.  (What do these letters indicate?) 

Choose "All Day".  Then click "Start Application".  It may take a few minutes; be patient.  When the three seismograms appear, look for evidence of the Central Italy quake.  "Zoom in" by dragging the yellow lines to the left and right to create a smaller "window"; then double-click the DMC button (the box under "Trace Access) to see the zoomed-in data.  You may have to try a few times; keep at it. 

Zoom in far enough that you can see the beginning of the P wave.  Read the time at which the P wave arrived (in yellow), and record it on the wiki page.
 
Third: Use the British Geological Survey seismogram data.   

Go to the Earth Science Department home page, then click "Terrific Links", then "Earthquake Watch", then "Seismogram Displays".  Click on the symbol on the United Kingdom on the world map .  Select one of the stations, and choose "Very Long Period".  Select April 6, 2009, and click "View". 

Find the Central Italy quake on this seismogram.  UTC time is on the right hand side.  Read these seismograms like you read lines in a book--from left to right, then continuing on the next line.  The different colors do not mean anything!  (They are there to help you see the lines more easily.) 

Finally: Send a group e-mail to me at L-Sanders [at] neiu.edu , giving your names, the station name, arrival times of the P and S waves, and the P-S lag.

Department of Earth Science | Northeastern Illinois University


Copyright 2009 Laura L. Sanders.  Last updated April 9, 2009.