✅1Q W3 | Lesson #1.2: Earthquakes and Earth's Internal Structure

Question 1

UCSB Science Line. The earth conducts seismic waves – when an earthquake occurs, stations farther and farther away from the quake see the S and P waves propagated through deeper and deeper layers. By measuring (_)

Answer 1

the arrival time of the seismic waves to worldwide stations, the velocity of the waves can be found as a function of depth.

Question 2

Seismic waves radiate out from the central point, called (_).

Answer 2

Focus or Hypocenter of an earthquake

Question 3

So, imagine throwing a stone/pebble in the water, it produces a ripple moving outward. These seismic waves are detected by highly sensitive instruments (_).

Answer 3

called seismometers and recorded by seismograph

Question 4

There is clear evidence for several layers in the earth which both (_) which the velocities are different.

Answer 4

refract the waves and reflect

Question 5

There is clear evidence for several layers in the earth which both refract the waves and reflect which the velocities are different. This may be due to the (_).

Answer 5

composition (chemical and mechanical), density and temperature of the earth’s layers.

Question 6

Seismic Waves and its Benefits

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Answer 6

• Measuring small earthquakes allows geologists to study areas underground.
• Geologists can measure the way that the vibrations of earthquakes travel and make inferences about the type of material the vibrations pass through.
• Geologists can find water aquifers, oil and natural gas deposits and other important resources based on information they gain from earthquakes. - Geologists can also measure the size and extent of these ARE.
• Earthquakes are the earth’s way of releasing energy stored in plate tectonics as they move. If plate tectonics could not move, the world would look dramatically different, with no mountains and distinctly smaller oceans. As plate tectonics move, it naturally cycles materials from the mantle of the earth.
• The seafloor that new material creates harbors thousands of species of plants and animals, which themselves play important roles in the human ecosystem by doing things like absorbing carbon dioxide and releasing oxygen through photosynthesis. Without the movement that allows earthquakes, none of this could occur on the earth.

Question 7

Seismologists study shock, or seismic, waves as they travel through (_)

Answer 7

the Earth’s interior.

Question 8

travel fastest and thus arrive first at seismic stations.

Answer 8

P waves, meaning primary waves

Question 9

arrive after the P waves.

Answer 9

The S, or secondary, waves

Question 10

The seismic waves called () pass through the core and are detected on the far side of the Earth. Indirect signals received in the () shadow zone suggest there is a solid inner core deflecting some waves.

Answer 10

P waves

Question 11

The seismic waves called S waves do not travel through (). We know that the outer core is () because of the shadow it casts in S waves.

Answer 11

liquid

Question 12

Due to our lack of access to the Earth’s interior, scientists must rely on indirect observations to learn about what is below the surface. One way they do this is by studying the movement of pressure waves as they travel through the interior of the Earth. This is called (_).

Answer 12

Seismology.