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 wave that crossed the inner core
   • The P wave
   • The S wave
2. 2.

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

   • It shakes the rock sideways
   • It moves through the liquid outer core
   • 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)?

   • Both P and S waves
   • Neither kind
   • P waves
   • 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?

   • 10 seconds
   • 14 seconds
   • 24 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
   • It cannot be told from lags
   • Station Y, with the longer lag
   • Station X, with the shorter 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)?

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

8. Use this

   Earth cutaway with a shaded band.

9. 7.

   Why are no direct S waves recorded beyond about 104° from a quake, by Pia's reading (USGS)?

   • S waves cross the core too fast to record
   • The solid inner core reflects them back
   • S waves fade out after 104 km
   • The liquid outer core stops S waves
10. 8.

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

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

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.

    In the USGS table, which listed layer is thickest, by Tala's reading?

    • The outer core, 2,259 km
    • The lower mantle, 2,171 km
    • The crust, 30 km
    • The inner core, 1,221 km
13. 10.

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

    • Mantle, crust, inner core, outer core
    • Crust, outer core, mantle, inner core
    • Crust, mantle, inner core, outer core
    • Crust, mantle, outer core, inner core