How earthquake waves reveal Earth's interior

Grade 9 Science Worksheet - Building Confidence

Circle the best answer.

1. 1.

   a first wave, then a second. Which wave reaches a seismograph first after an earthquake, by Ari's reading (USGS)?

   • Both at the same moment
   • The S wave
   • The wave that crossed the inner core
   • The P wave
2. 2.

   How does an S wave move rock as it passes, by Bo's reading (USGS)?

   • It moves through the liquid outer core
   • It shakes the rock sideways
   • It travels faster than the P wave
   • It squeezes and stretches rock along its path
3. 3.

   P and S waves meeting a liquid layer. Which waves can travel through a liquid, by Kira's reading (USGS)?

   • Neither kind
   • P waves
   • S waves
   • Both P and S waves
4. 4.

   Note: model speeds P 6 km/s, S 3.5 km/s. At a station 84 km from a quake, P arrives after 14 s and S after 24 s (model speeds). What is the S-minus-P lag, by Jun's math?

   • 14 seconds
   • 24 seconds
   • 10 seconds
   • 38 seconds

5. Read this first

   Table, Model lag table, with columns Lag, Distance

   10 s, 84 km; 25 s, 210 km; 50 s, 420 km. Note: model speeds P 6 km/s, S 3.5 km/s.

6. 5.

   Station X records an S-minus-P lag of 10 s, and station Y a lag of 50 s. Which station is closer to the quake, by Luz's reading?

   • Both are the same distance
   • Station X, with the shorter lag
   • It cannot be told from lags
   • Station Y, with the longer lag
7. 6.

   Three stations with circles around them. Why do seismologists use records from several stations to find a quake's epicenter, by Milo's reading (USGS)?

   • More stations make the waves travel faster
   • Each lag gives a distance, and arcs from several stations meet at one point
   • Stations measure the quake's color
   • One station's lag gives the exact spot

8. Use this

   Earth cutaway with a shaded band.

9. 7.

   What is the P-wave shadow zone, by Noah's reading (USGS)?

   • Where S waves arrive before P waves
   • The whole far side of Earth
   • A band from 104° to 140° from a quake with no direct P waves
   • A place where the ground goes dark
10. 8.

    What bends P waves and makes their shadow zone, by Ren's reading (USGS)?

    • Refraction at the liquid core
    • S waves blocking them
    • Absorption by the oceans
    • Reflection off the crust

11. Data on the Earth's interior (USGS)

    Layer	Thickness
    crust	30 km
    upper mantle	720 km
    lower mantle	2,171 km
    outer core	2,259 km
    inner core	1,221 km

12. 9.

    Put the layers in order from the surface down, by Zee's reading (USGS).

    • Crust, mantle, outer core, inner core
    • Mantle, crust, inner core, outer core
    • Crust, mantle, inner core, outer core
    • Crust, outer core, mantle, inner core
13. 10.

    What is the Moho, by Esme's reading (USGS)?

    • The boundary between the liquid outer core and the inner core
    • A wave that circles Earth's surface
    • The crust-mantle boundary, where wave speed jumps up
    • A zone where waves come to a stop