Lecture 22 - Earthquakes Part 1

Question 1

earthquake

Answer 1

a sudden and violent shaking of the ground as a result of movements within the earths crust or volcanic activity

Question 2

quake

Answer 2

to shake or tremble

Question 3

seismic

Answer 3

relating to earthquakes or other vibrations of the earths and its crust

Question 4

seismology

Answer 4

the study of earthquakes

Question 5

seismologist

Answer 5

scientist who studies earthquakes

Question 6

how many earthquakes are there each year

Answer 6

500,000

Question 7

how many of the 500,000 earthquakes per year are felt by humans. and how many of these cause damage or death

Answer 7

100,000

100 cause damage or death

Question 8

since the start of october 2023, multiple earthquakes have hit western afghanistan. ho many people have died or been injured by this

Answer 8

1500 people died and 2000 injured

Question 9

earths entire crust and upper mantle (ie, lithosphere) can be subdivided into ____

Answer 9

large rocky plates known as tectonic plates

Question 10

the lithosphere is divided into how many major and minor tectonic plates

Answer 10

7 major
8 minor

Question 11

where does the lithosphere (and therefore tectonic plates) sit on

Answer 11

the asthenosphere

Question 12

asthenosphere

Answer 12

partially molten layer of mantle

Question 13

why how/why asthenosphere move

Answer 13

move due to heat transfer and rise and fall of partially molten rocks within it

Question 14

when asthenosphere below moves, what happens to tectonic plates

Answer 14

tectonic plates are dragged along and move too

Question 15

what does friction do

Answer 15

friction where plates meet may slow and/or prevent their motion, resulting in a build up of pressure

Question 16

what is friction

Answer 16

• resistance a surface or object encounters when moving over another
• a force that opposes motion (sliding, rolling) of one object over another

Question 17

what happens after pressure build up for so long, what does it cause and what is it called

Answer 17

plates overcome friction and move, releasing built-up as seismic waves

when this occurs, section of earths crust can literally break apart and be displaced, resulting in an earthquake

this is called a tectonic earthquake

Question 18

what percentage of large tectonic earthquakes occur along the “circum-pacific seismic belt” along the rim of the Pacific Ocean

Answer 18

a majority — 81%

Question 19

what is the “Circum-pacific seismic belt” known for

Answer 19

home to some of the worlds most powerful volcanoes and is known as the ring of fire

Question 20

what are other examples of earthquake zones

Answer 20

• alpide belt (home to the recent afghanistan earthquakes)
• mid-atlantic ridge (where divergent plate boundaries are encountered)

Question 21

what is the hypocenter

Answer 21

point in earths interior where earthquake originates

Question 22

what is epicenter

Answer 22

• point on earths surface directly above the hypocenter
• point on earths surface where seismic waves are fist felt/where waves first arrive

Question 23

what are seismic waves

Answer 23

vibrations that travel through (body of) earths or along its surface when earthquake occurs

Question 24

what are the different movements of seismic waves

Answer 24

• some move/travel through earth (body waves)
• some move/travel along earths surface (surface waves)

Question 25

what are the 2 types of body waves that travel through earth

Answer 25

- p-waves (short for primary waves) named this way as they are first waves detected by seismic recording stations (that monitor earthquake activity) following an earthquake - s-waves (short for secondary waves) arrive at seismic recording stations after the p-wave

Question 26

what do p-waves do

Answer 26

- cause surface of earth to expand and contract in direction of wave travel (parallel to wave travel) - can travel solid, liquids, and gases

Question 27

what do s-waves do

Answer 27

- cause surface of earths to rise and fall - surface moves perpendicular to direction of wave travel - can travel though solids

Question 28

where can p-waves travel

Answer 28

- can travel through solids, liquids, and gases - can travel through crust, mantle, outer core (which is liquid) and inner core (which is solid)

Question 29

where can s-waves travel

Answer 29

- can travel trough solids - can travel through crust and mantle - cannot travel through outer core (which is liquid) and therefore never reach inner core (which is solid)

Question 30

surface waves follow ____

Answer 30

the faster body waves (ie p-waves and s-waves)

Question 31

characteristic of surface waves

Answer 31

- surface waves are much slower than body waves - surface waves only travel along earths surface - surface waves only travel through solids - surface waves more destructive than body waves

Question 32

what are the 2 types of surface waves (that travel along earths surface)

Answer 32

- love waves (the faster of the two) - rayleigh waves

Question 33

which is faster love waves or rayleigh waves

Answer 33

love waves

Question 34

what are love waves

Answer 34

- travel horizontally - cause earths surface to move form side to side, perpendicular to direction of wave motion

Question 35

what are rayleigh waves

Answer 35

- travel horizontally - case maths surface to shale in an elliptical pattern (ie. rolling pattern) - cause earths surface to move like ocean waves - spread out most (of all waves) and last for longest period of time