How earthquake waves reveal Earth's interior

Grade 9 Science Worksheet

Circle the best answer.

1. 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.

2. 1.

   A station's lag is 50 s. Using the model lag table, about how far away is the quake, by Esme's reading?

   • About 50 km
   • About 84 km
   • About 420 km
   • About 210 km
3. 2.

   Three stations with circles around them. Three stations each find their distance to one quake. How is the epicenter found, by Jun's reading (USGS)?

   • Average the three distances
   • Draw a circle of that radius around each station; they meet at the epicenter
   • Pick the station with the largest lag
   • Use the first station by itself
4. 3.

   From mantle to core, wave speed drops about 30% (USGS). A model P wave at 10 km/s just above the core would travel about how fast just below, by Luz's math?

   • About 10 km/s, unchanged
   • About 13 km/s
   • About 3 km/s
   • About 7 km/s
5. 4.

   Why do earthquake wave paths curve inside Earth, by Milo's reading (USGS)?

   • Waves follow straight lines at one speed
   • Rock at different depths changes the waves' speed
   • Earth's spin bends them
   • The Moon's pull bends them

6. Use this

   Earth cutaway with a shaded band.

7. 5.

   Station 1 sits 60° from a quake, station 2 at 120° and station 3 at 150°. Which one sits in the P-wave shadow zone, by Noah's reading (USGS)?

   • Station 1, at 60°
   • Stations 2 and 3
   • Station 2, at 120°
   • Station 3, at 150°
8. 6.

   Of those stations at 60°, 120° and 150°, which records direct S waves, by Pia's reading (USGS)?

   • Stations 1 and 3
   • Station 1, at 60°
   • Station 2, at 120°
   • Station 3, at 150°
9. 7.

   Oldham identified Earth's core from earthquake records in 1906 (USGS). Which observation shows the outer core is liquid, by Ren's reading?

   • Its waves arrive before the P waves
   • Its P waves speed up sharply
   • It does not transmit S waves, and P waves slow sharply
   • It transmits S waves faster than the mantle

10. 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

11. 8.

    Using the USGS thicknesses, how deep is the top of the outer core, by Tala's math?

    • About 5,180 km
    • About 750 km
    • About 2,921 km
    • About 2,171 km
12. 9.

    Using the USGS thicknesses, how deep is the top of the inner core, by Zee's math?

    • About 6,401 km
    • About 2,259 km
    • About 5,180 km
    • About 3,480 km
13. 10.

    A drill hole on the Kola Peninsula reached 12 km (USGS). About what share of the 6,401 km to Earth's center is that, by Ari's math?

    • About 0.2%
    • About 20%
    • About 12%
    • About 2%