North Seattle Community College's
PHYSICAL GEOLOGY 101
Instructor:  Tom Braziunas

 

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Boat Beached by Tsunami, 1964 Alaska Earthquake
NOAA Public Domain Photograph*

Earthquake Lab

@2002 -- The information contained in this document is copyrighted.
No reproduction may be made without prior approval from the author (Dr. Tom Braziunas).

 

I. Introduction:

The Internet offers some excellent learning tools developed by educators and public agencies.  We can also access sophisticated research tools online in order to gather instant information and immediately analyze the data.  In this week's lab, we have a chance to sample both the educational and the research power of the Web!  The lab exercise this week questions which are worth from 2 to 6 points each for a possible 50 POINTS TOTAL.

*All photographs shown in this lab exercise are online at:
  http://www.ngdc.noaa.gov/seg/hazard/slideset/earthquakes/

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Damage to Railway by 1965 Seattle Earthquake
NOAA Public Domain Photograph

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II.  Earthquake Epicenters and Magnitudes:

An excellent Internet educational tool has been developed to step students through the process of locating the epicenter of an earthquake and determining its magnitude on the Richter scale.  This interactive "Virtual Earthquake" activity is part of a series of "Geology Labs On-Line." These labs were designed by Gary A. Novak of the California University at Los Angeles and supported by grants from the US National Science Foundation and the California State University System. 

The learning module nicely steps us through the analysis and completes the calculations.  Please write down your answers along the way so that you can copy them to the submission form for this lab.  

Click here to begin.  Read through and complete each step.  Choose the Japan region for simulating the earthquake.

Question 1 (2 points). What are the three seismic stations and what are the three S-P interval times for these three seismic stations?

Question 2 (6 points). Convert the three S-P interval times to distances using the travel-time graph provided.  (NOTE:   This activity adds another curve to the travel-time graph which we have used before.  The S-P curve is simply the difference in the S curve and P curve that is shown in your lab manual's travel-time graph for earthquake waves.)  These three distances are: ____________

Question 3 (2 points).  Compare your calculated epicenter location with the true epicenter location.  Where is the true epicenter in latitude and longitude?  Click here to link to an Internet program which will provide latitude and longitude information on any city in the world.  Select the "Astrodienst Atlas" option and input the city closest to the epicenter location.  This city and its geographic coordinates are: ______________________ 

Question 4 (2 points).  Now we will proceed to calculate the magnitude of this earthquake.  Follow the instructions in the online module.  What are the three S wave amplitudes you measured?

Question 5 (2 points).  What is your estimate for the Richter magnitude of the earthquake and how does it compare to the true magnitude?

Question 6 (2 points).  Complete the final form and receive your Certificate of Completion.  Copy and paste it into the space provided for this answer on your lab submission form. 

Question 7 (2 points).  Pick a city in the world where a seismic station would only receive P waves but not the S waves from this earthquake.  You will need to use a globe or world map in order to make your choice.   (A good online resource is this website: http://go.hrw.com/atlas/norm_htm/world.htm.)  Name the city and its country and explain why it would not receive the S waves from this earthquake.

Question 8 (2 points).  Pick a city in the world where a seismic station would receive neither the P waves nor the S waves from this earthquake.  Name the city and its country and explain why it would not receive the P or the S waves from this earthquake.

 

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Aerial view of San Andreas fault
NOAA Public Domain Photograph

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III.  Online Information on Current Earthquakes:

The National Earthquake Information Center provides immediate access to information on earthquakes as they are being recorded.  Such a web resource allow us (and many other geologists) to utilize and interpret data collected across the globe.  Let's learn more about this resource by using a few of its many features.

Click on the following URL to link to the NEIC.  http://neic.usgs.gov/ .  Then click on "Current Earthquakes." 

Question 9 (2 points).  What are the locations of the 5 highest magnitude earthquakes to have occurred in the last 3 days? 

Question 10 (2 points). What were their calculated magnitudes? 

Question 11 (2 points). Which one is closest to where you live? Which one is the farthest? 

Question 12 (2 points).  How long would it take the P waves to reach your house in both cases? (In order to get this information, click on the locations of each of these two earthquakes.  Then scroll down to and click on the "Theoretical P-Wave Travel Times" link.

Return to the homepage for the NEIC and click on "Current Earthquake Information." From this web page, click on  "Earthquake Activity in the Last Thirty Days" to view a world-wide map showing location, magnitude (size of the earthquake circles) and depth (color of the earthquake circles).  A more detailed map view for each area of the world can be accessed through the "Current Earthquake Maps" link.

Question 13 (6 points). What geographic area on the world had the most shallow earthquakes over the last 30 days?  Which geographic area had the most deep earthquakes?  Which geographic area had the strongest earthquakes overall (regardless of depth)?  

Question 14 (6 points).  What types of plate boundary (or non-boundary) is each of these three geographic areas?  Do each of these plate boundaries fit with the types of earthquakes which have occurred there?  Explain

Question 15 (2 points). Name an earthquake (according to its location) which has occurred over the last 30 days in a non-plate-boundary setting.  You will need to click on the "Current Earthquake Maps" and explore the world a little bit.  What is your educated guess as to a possible source for such a non-plate-boundary earthquakes? 

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Damage from the Armenian SSR Earthquake, December 7, 1988
NOAA Public Domain Photograph

IV.  Pacific Northwest Earthquakes:

Finally, we will visit the University of Washington Seismology Lab website (at http://spike.geophys.washington.edu/SEIS/PNSN/ ).  This world-renowned website is maintained by the  UW Geophysics Department which we will be visiting in an optional field trip at the end of this quarter.  This rich online resource is the first place to check for important updates on hazard conditions when a local quake has occurred.  

Click on "Latest PNW Earthquakes" to view a map showing the magnitudes, locations, and dates of the earthquakes which have occurred locally over the last two weeks.

Question 16 (4 points). For the strongest recent Pacific Northwest earthquake of the last two weeks, what was its magnitude, time of occurrence, distance from a major city, geographic coordinates, depth and topographic setting? (You will need to click on the square that shows that earthquake in order to get this detailed information.) 

Return to the main Seismology Lab web page and click on "Volcano Quakes."  Select the Mt. St. Helens link and then click on the "Mt. St. Helens swarms" from November, 2001.  Look at some of the Web-recorder data for these swarms.  This information is presented as if it were actually produced on a standard seismograph.

Question 17 (4 points). Let's practice reading one of these plots.  Click HERE.  About how long (in seconds) did each of these tiny earthquake events last?  When (date and time to the nearest minute if possible) did the largest earthquake occur on this graph?

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Izmit (Kocaeli) Turkey Earthquake, August 17, 1999
NOAA Public Domain Photograph