lab 9 -- earthquakes

By Vivian Webb,2014-04-08 20:44
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lab 9 -- earthquakes

Geology 101 (20 points) Name(s):

    Earthquakes and Seismic Hazards in Washington State

Calibrating the sensitivity of the Green River Seismometer:

    ; In the space below draw a representation of the signal on the GRCC seismograph before our


    ; In the space below draw a representation of the signal on the GRCC seismograph after test

    jump #1 (right next to the seismometer):

    ; In the space below draw a representation of the signal on the GRCC seismograph after test

    jump #2 (10 meters away from the seismometer):

     How far away do you have to jump before the signal is not evidence on the seismograph?


    Estimating Earthquake Hazards & Effects:

     Information on Earthquake Hazards in the Greater Seattle Area can be found on the United States Geological Survey’s website at: (

    ; Examine Figure 1 on the website (or figure 1-28 in your book) and draw a cross section (side-view)

    diagram that shows the relationship between the Pacific Plate, the Juan de Fuca Plate and the North

    American Plate in the space provided below. Clearly show the location of and label the convergent

    plate boundary and the divergent plate boundary.

    West East

     Answer the questions below using the map provided or the electronic version of the map on the website listed above (you’ll find it if you scroll down to the “Earthquakes effects” section at the bottom of the

    View 266 kb full-color Lifelines map.) Note: There is a link for a larger/ easier to page and click on the link for “

    read version of the legend for this map at the bottom of the map.

    ; Examine the Kent River valley (it is the valley that runs parallel to highway 167) and the Auburn Area

    (by the intersection of 167 and 18). What kind of deposits (bedrock or loose sediment) is found in

    each area?

    ; Does the presence of these kinds of deposits increase or decrease the probability of liquefaction and

    the amount of seismic shaking during an earthquake? (If you are not sure how to answer this questions

    read the section on “Attenuation and Amplification.”)

    ; How wide and how long is the zone of probable ground rupture along the Seattle Fault?

    ; What part of the city of Seattle is built in this fault zone? (If needed: you can check out a map of

    downtown Seattle at


    ; What parts of Seattle would be most vulnerable to earthquake damage (which parts are built on

    unconsolidated sediments)?

    ; Which major roads in the Puget Sound area cross the Seattle Fault zone of probable ground rupture?

    How would this effect emergency rescue teams after an Earthquake?

Determine how many of each type of the lifelines listed below cross the Seattle fault zone and list at least one

    secondary hazard (danger that occurs after the earthquake) that would results from the disruption of each lifeline. Explain your reasoning.

    ; Major electrical line:

    ; Major water supply line:

    ; Major sewer line:

    ; Natural gas pipeline:


Locating the Epicenter of an Earthquake:

     We will now look at data from a theoretical earthquake and determine the epicenter of an Earthquake. Scientists can determine distance to an Earthquake by noting the difference between the arrival of the fast

    moving Primary waves (p-waves) and the slower moving Secondary (S- waves). Go the website listed below and fill in the information requested below:

    Select the option for a San Francisco area earthquake and fill in the information below. Then go back to the first page and do the same for the Japan Region Earthquake.

    Epicenter Distance: Use these three seismograms provided to estimate the S-P time interval for each of the recording stations. Record your measurement below:

     San Francisco Area Earthquake Japan Region Earthquake

    Station S-P Interval Station S-P Interval

    Eureka, CA seconds seconds Pusan Station

    Elko, NV seconds seconds Tokyo Station

    Las Vegas, NV seconds seconds Akita Station

    Determining Distance from S-P: Use the S-P graph on this webpage and the estimates you made for the S-P time intervals for the three seismograms (listed above) to complete the table below. The horizontal grid is in

    one second intervals.

    San Francisco Area Earthquake Japan Region Earthquake

     Station Epicenter Distance Station Epicenter Distance

     Eureka, CA Pusan Station KM KM

     Elko, NV Tokyo Station KM KM

    Las Vegas, Akita Station KM KM NV

; When you’ve recorded the distances, click the Epicenter button to see how you did then

    describe how your result compare the actual figures and list them below. Note if your

    calculation was 100% correct- then put down “0” for the error.

    San Francisco Actual Difference from Japan Actual Epicenter Difference from

    Recording Distance your Recording Distance your calculations

    Station (km) calculations Station (km)

     Eureka, CA Pusan

     Elko, NV Tokyo

     Las Vegas, NV Akita

    ; What was you’re biggest source of error (if any)?


Maps from the United States Geological Survey website

Washington Earthquakes: Time and date of your observations on the web:

    How many earthquakes have there been in the state of Washington and surrounding area?

the last 2 hours: the last 2 days: the last 2 weeks:

    (Hint: If you have trouble estimating the total amount of earthquakes, check the listed number of total earthquakes on the map over the last 2 weeks in the lower right hand corner.)

    ; What part of the state has the highest number of earthquakes (West, North, South, or East)? Explain

    why there is an unequal distribution of earthquakes across the state.

    ; What is the location and magnitude of the largest Earthquake on this map and when did it occur? (Hint:

    scrolling down and checking under the link for “Big Earthquake List” may help if you have trouble

    estimating this from the map.)

    ; Check out the “special map for Mt. St. Helens.” How many of the earthquakes in the last two weeks

    occurred at Mt. St. Helens. What geologic feature explains these earthquakes?

    ; How many of the Earthquakes in the last two weeks occurred in the Seattle Region?

    On February 28, 2001 a 6.8 Earthquake struck the Puget Sound Region. The epicenter of this earthquake was 17 km NE of Olympia. The focus was 52 km below the surface. A map showing how much the ground shook in this earthquake can be found at: Examine

    the map answer the questions below.

    ; Which city is closer to the epicenter (it’s marked on the map by the black star): Tacoma or Seattle?

    ; What degree of shaking, according to the map, was there in the Kent Valley/ Auburn Area?

    ; What was the level of perceived shaking/damage in Tacoma vs. Seattle? Suggest a reason for this

    observed pattern (hint: consider the “Lifelines and Earthquake hazards in the Greater Seattle Area



US Earthquakes: Click on the link for US Earthquakes or go to:

    ; How many earthquakes in total were there in the US in the last week

     (No you don’t have to count them- the total is listed in the upper left hand corner of the box)

    ; Which 2 neighboring states on the map of the Conterminous 48 States had the most earthquakes-

    and how many earthquakes did they have ( = click on the state with the most earthquakes to zoom in

    and get the total number).

    ; What type of plate boundary is associated with these Earthquakes? (hint: check figure 10-3 or 1-21 in

    your book if you can’t remember).

    ; Check the list labeled M>3 earthquake listand list the dates, magnitudes, and locations for the

    five largest Earthquakes that have occurred in the last week in the United States.

     Date Magnitude Location






    ; Which state has the most earthquakes with magnitude (M) > 4.5? What type of plate boundary is

    associated with these earthquakes? (Hint: check figure 10-3 or 1-21 in your book.)

    ; Click on the link for Alaska under the list of “USA Regional Maps. How many earthquakes

    occurred in Alaska over the past week and how does this compare to the number in California?


    ; Where do most Earthquakes occur in Alaska? What geologic feature accounts for this pattern? (If

    needed, you can review pages 402-403 or your text):

    Fill out the table below that summarized how the earthquakes in Washington State compare with those in California, the Midwest, Alaska, and the East Coast

     Which region has largest EQ

    Which region listed has the (the EQ w. the biggest magnitude)

    most EQ?

Washington vs. California: Washington or California: Washington or California:

Washington vs. the Midwest: Washington or the Midwest: Washington or the Midwest:

     (middle of the country)

Washington vs. the East Coast: Washington or the East Coast: Washington or the East Coast:

Washington vs. Alaska Washington or Alaska Washington or Alaska

    ; Click on the link for Hawaii and examine the detailed map of Hawaii. Which of the Hawaiian Islands

    has the most earthquakes? What accounts for this pattern? (If needed, you can review Hawaiian

    geography on page 402-403 or your text):

    ; How many earthquakes have occurred and what is the magnitude of the large earthquake that has

    occurred in Hawaii in the last week?


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