Core - Topic 1.4 - Earthquakes and Sound

Question 1

The noise from the explosion was described as the loudest sound ever detected
on Earth.
However, human beings could not hear this sound.
State the two sound frequency ranges that human beings cannot hear.

Answer 1

below 20 Hz (1)
 above {20 000 Hz / 20 kHz}
(1)
If Hz or kHz is not seen
somewhere, the maximum
score is 1 mark.

Question 2

Explain why the path of the P-wave is not a straight line.

2

Answer 2

Explanation linking the
following:-
MP1 refraction /changing speed
(1)
MP2 (due to) changing
{material/medium /rock
type / density} (1)

Question 3

Explain why there are regions on the Earth’s surface where S-waves from the
collision at X cannot be detected. You can add to the diagram to help your
answer.
(3)

Answer 3

Explanation linking the
following:-
MP1 (S / transverse waves)
they cannot travel through
liquid (1)
MP2 Earth’s core is (at least
part) {liquid/molten} (1)
MP3 (so) (S waves) they
cannot travel through core
(to other side of Earth) (1)

Question 4

Describe how a meteor colliding with the Earth could set off an earthquake.
(2)

Answer 4

Suggestion to include any two
from:
MP1 idea that {kinetic
energy/force/ momentum}
of meteor might cause the
earthquake (1)
MP2 (earthquakes happen
where) plates slide
{past/over/under/away
from/against} each other
(1)
MP3 (plates move) suddenly
MP4 (meteor collision) starts
seismic waves /P/S (1)

Question 5

(a) A man uses a dog whistle to call his dog.
The whistle uses ultrasound.
(i) The dog can hear the whistle but the man cannot.
Explain why the dog can hear the whistle but the man cannot hear the
whistle.
(2)

Answer 5

an explanation linking:
 frequency / Hz (1)
 above 20 000 (1)

Question 6

The dog is 140 m away from the man.
The ultrasound takes 0.42 s to travel from the man to the dog.
Calculate the speed of ultrasound.
State the unit.
(3)

Answer 6

substitution: (1)
140/0.42
evaluation: (1)
330
m/s (1)

Question 7

Earthquakes occur when two tectonic plates move against each other.
Explain what causes the tectonic plates to move.
You may draw a diagram if it helps your answer.
(2)

Answer 7

Explanation linking:
 convection (currents) (1)
 in mantle (1)
Accept answers in form of a
labelled diagram
in molten rock
in magma
below plates
in the hot rock
coming from the core
under Earth’s crust
under surface
ignore lava
clear unlabelled diagram scores
maximum 1 mark
clear labelled diagram

Question 8

An earthquake occurs.
Its epicentre is at the place marked E on the diagram.
Describe what happens at the plate boundary to cause this earthquake.
(2)

Answer 8

A description linking
plates move / slip / separate
(relative to each other) (1)
sudden (release of energy) (1)

Question 9

The earthquake causes seismic waves.
(i) S waves are one type of seismic wave. They travel at 0.65 km/s.
There is a seismometer 80 km away from point E.
Show that it takes about 2 minutes for the S waves from the earthquake to
reach the seismometer.
(2)

Answer 9

substitution (1)
0.65 = 80 / t
transposition (1)
t = 80 / 0.65
(123 seconds)

Question 10

P waves are another type of seismic wave.
They travel about 10 times more quickly than S waves.
Describe how scientists can use seismometer records of P and S waves to
locate the epicentre.

Answer 10

A description linking any three
detection of arrival of P and S
waves (1)
measurement of difference in
arrival times (1)
calculation of distance (from
epicentre to station) (1)
triangulation/using three /
several stations (1)

Question 11

Seismic waves have a frequency of about 15 Hz.
P waves have a much smaller amplitude than S waves.
Some people claim that animals can detect an earthquake before people are
aware of it.
Suggest an explanation for this.
(2)

Answer 11

A suggestion including any two of
the following
Infrasound (1)
some animals can hear waves
below human frequency range /
20 Hz (1)
they could hear P waves arriving
before the (stronger) S waves
arrive (1)

Question 12

A dolphin is near to a group of fish.
Describe how a dolphin uses high frequency sound to locate the position of
the fish.

Answer 12

Any 3 from
• emits (high frequency/ultra)
(sound)(1)
• (sound is) reflected (off fish)
(1)
• (reflection) detected by Dolphin
(1)
• dolphin (estimates) time between
(sending and receiving) sounds
(1)
• dolphin is able to change time into
(estimate of) distance (1)

Question 13

A small explosion is triggered at the Earth’s surface.
The waves reflect back from the top of the oil field.
Suggest why the waves are reflected from the oil field.
(1)

Answer 13

(there is a) difference/change in

density (1)

Question 14

A wave has a frequency of 15 Hz.
Its wavelength is 125 m.
Calculate the speed of the wave.
State the unit.

Answer 14

Substitution into correct
equation(1)
v = 15 x 125
Evaluation (1)
1875
Unit (1)
m/s