(Stnd 17) Study Guide-Seismic Waves and Earth's Structure

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An earthquake occurred at a plate boundary in California as huge blocks of the Earth’s crust slipped past one another. The Pacific plate is moving northwest past the North America plate at this boundary at a rate of about 50 millimeters (about 2 inches) each year. Seismographs at several locations detected and measured the seismic waves from this earthquake, and the P-Wave data is shown below. Examine the following table of seismic data.

Two-Part Question
1) What is one key difference between P-Waves and S-Waves?
2) Which instruments do scientists use to detect and measure seismic waves?

a.	1) S-Waves are the second wave felt in earthquakes. 2) Vibeometers
b.	1) S-Waves are faster than P-Waves. 2) Seismograms
c.	1) P-Waves are faster than S-Waves. 2) Seismographs/seismometers

Examine the information in Seismic Data Table 02 to answer this question.
Speed changes and refraction has been observed in seismic wave data as the waves travel through different substances with different densities.
What is one location where this is revealed in Seismic Data Table 02, and what best explains this phenomenon?

a.	At a depth of 50 kilometers the S-Waves increased speed from 4 km/s to 5 km/s. This occurred as the wave hit the boundary of the inner core and the outer core.
b.	At a depth of 50 kilometers the S-Waves slowed from 5 km/s to 4 km/s. This occurred as the wave hit the boundary of the crust and the mantle.
c.	At a depth of 5200 kilometers the S-Waves slowed from 14 km/s to 8 km/s. This occurred as the wave hit the boundary of the crust and the mantle.

Examine the information in Seismic Data Table 01 to answer this question.
Layers of rock inside the Earth have been revealed by analyzing seismic data. Geologists have observed that seismic waves change speed as they move downward toward Earth’s center.
What is one location where this is revealed in Seismic Data Table 01, and what best explains this phenomenon?

a.	At a depth of 3000 kilometers the P-Waves decreased speed from 9 km/s to 8 km/s. This occurred as the wave hit the boundary of the crust and the mantle.
b.	At a depth of 2900 kilometers the P-Waves slowed from 14 km/s to 8 km/s. This occurred as the wave hit the boundary of the mantle and the outer core.
c.	At a depth of 1000 kilometers the P-Waves stopped. This occurred as the wave hit the boundary of the mantle and the outer core.

Examine the information in Seismic Data Table 02 to answer this question.
Refraction and changes in speed have been observed in seismic wave data as the waves travel towards the center of our planet.
What is one location where this is revealed in Seismic Data Table 02, and what best explains this phenomenon?

a.	At a depth of 2900 kilometers the S-Waves slowed from 5 km/s to 4 km/s. This occurred as the wave hit the boundary of the crust and the mantle.
b.	At a depth of 5200 kilometers the S-Waves slowed from 14 km/s to 8 km/s. This occurred as the wave hit the boundary of the crust and the mantle.
c.	At a depth of 2900 kilometers the S-Waves slowed from 7.5 km/s to 0 km/s. This occurred because S-Waves are unable to travel through liquid rock.

How did geologists learn that the Earth has multiple-layers inside it including the crust, the mantle, the outer core, and the inner core?

a.	They chemically analyzed Earth rocks and compared them to rocks from Mars.
b.	They studied star constellations and noticed patterns in the way celestial objects move.
c.	By analyzing seismic data and noticing patterns as waves move through the Earth.

Examine the information in Seismic Data Table 01 to answer this question.
What is the primary cause of seismic waves, and what pattern do you notice about the P-Waves as they propagated downward towards the center of our planet?

a.	Seismic waves mainly occur when massive celestial objects impact the Earth. The P-Waves maintain a constant speed as they the move through our planet.
b.	Seismic waves mainly result from tectonic plate movement. The P-Waves slow down as they move through different rock layers within the Earth.
c.	Seismic waves mainly occur beneath the seas due to the mass of the water. P-Waves speed up as they travel down towards the center of the Earth.

Examine the information in Seismic Data Table 01 to answer this question.
Seismic waves refact and change speed as they move through substances with different densities.
What is one location where this is revealed in Seismic Data Table 01, and what best explains this phenomenon?

a.	At a depth of 50 kilometers the P-Waves decreased speed from 9 km/s to 8 km/s. This occurred as the wave hit the boundary of the crust and the mantle.
b.	At a depth of 2900 kilometers the P-Waves slowed from 7.5 km/s to 0 km/s. This occurred because P-Waves are unable to travel through liquid rock.
c.	At a depth of 5200 kilometers the P-Waves slowed from 14 km/s to 8 km/s. This occurred as the wave hit the boundary of the crust and the mantle.

a.	At a depth of 5200 kilometers the P-Waves slowed from 11 km/s to 10 km/s. This occurred because P-Waves are unable to travel through solid rock.
b.	At a depth of 2900 kilometers the P-Waves decreased speed from 9 km/s to 8 km/s. This occurred as the wave hit the boundary of the outer core and inner core.
c.	After 5200 km, P-Wave speed was a constant 11 km/s all the way to Earth’s center. This occurred as the wave moved from the outer core through the inner core.

Examine the information in Seismic Data Table 02 to answer this question.
P-Waves can travel through both solid and liquid rock. S-Waves, on the other hand, can only travel through solid rock.
What is one location in Seismic Data Table 02 where liquid rock is revealed by the S-Wave data?

a.	At a depth of 2900 kilometers the S-Waves stopped. This occurred because after 2900 km there is a layer of liquid rock.
b.	At a depth of 50 kilometers the S-Waves increased speed from 4 km/s to 5 km/s. This occurred as the wave hit the boundary of the inner core and the outer core.
c.	At a depth of 2900 kilometers the S-Waves slowed from 5 km/s to 4 km/s. This occurred as the wave hit the boundary of the crust and the mantle.

10.

Analyze the P-Wave and S-Wave speed patterns in Seismic Data Table 01 and 02. Then select the model below which best matches the data.

Model One

Model Two

Model Three