Chapter 10 - Earthquakes and Earth's Interior

Question 1

Seismology

Answer 1

Study of earthquakes

Question 2

Seismometer

Answer 2

used to record shocks and vibrations from earthquakes

Question 3

Inertial Seismometer

Answer 3

Relies on resistance of stationary mass to movement

Question 4

Focus

Answer 4

point where earthquake starts to release elastic strain of surrounding rock

Question 5

Epicenter

Answer 5

point on earth’s surface lying vertically above focus

Question 6

Seismic Waves

Answer 6

vibrational waves that spread out in all directions initially from focus

Question 7

Body waves

Answer 7

seismic waves that travel through earth’s interior

Question 8

Primary (P) Wave

Answer 8

compressional - can pass through solids or fluids - rock vibrates back and forth in line of wave motion - fastest

Question 9

Secondary (S) Wave

Answer 9

cannot pass through fluids - rock moves sideways perpendicular to direction of wave travel - slower that P waves

Question 10

Surface Wave

Answer 10

pass around earth rather than through it - slower than either P waves or S waves - different wavelengths develop different velocities (dispersion)

Question 11

Determining Epicenter

Answer 11

locate from arrival times of P waves and S waves at 3 or more seismometers

Question 12

Richter Magnitude Scale

Answer 12

estimated by measuring amplitudes of seismic waves - divided into steps representing 30 times increase in energy

Question 13

Earthquake Hazard

Answer 13

most large earthquakes occur along plate boundaries - seismic risk maps based on acceleration relative to gravity used to design roadways and public buildings

Question 14

Earthquake Disasters

Answer 14

Based on number of people killed

Question 15

Earthquake Damage

Answer 15

1) Ground motion - 2) displacement along faults - 3) fire - 4) landslides - 5) liquefaction - 6) tsunamis

Question 16

Ground Motion

Answer 16

results from movement of seismic waves: especially surface waves

Question 17

Displacement Along Faults

Answer 17

Features that cross or sit on faults can be broken

Question 18

Fire

Answer 18

started by broken gas mains and electrical wires - water mains also broken

Question 19

Landslides

Answer 19

earthquakes may trigger rapid mass wasting movements

Question 20

Liquefaction

Answer 20

shaking can turn saturated sediment/regolith into liquid mass

Question 21

Tsunamis (Seismic Sea Waves)

Answer 21

High velocities - low amplitude in deep water but dramatic increase in shallow water

Question 22

Modified Mercalli Scale

Answer 22

Based on amount of vibration felt and building damage - depends on distance from epicenter as well as magnitude

Question 23

World Distribution

Answer 23

plate boundaries most subject to frequent earthquakes

Question 24

Circum-Pacific Belt

Answer 24

accounts for 80% of all earthquakes

Question 25

Mediterranean Himalayan Belt

Answer 25

accounts for 15% of all earthquakes

Question 26

Benioff Zone

Answer 26

depth of focus up to 700km

Question 27

First Motion Studies

Answer 27

can determine movement direction if fault orientation is known

Question 28

Elastic Rebound Theory

Answer 28

Energy stored in elastically deformed rock bodies - when fault slips rocks rebound to original shapes

Question 29

Seismic Gaps

Answer 29

Strain is steadily increasing but no earthquakes for a long time

Question 30

Earthquake Precursors

Answer 30

One case of odd animal behavior before earthquake

Question 31

Foreshocks

Answer 31

smaller earthquakes preceding a large earthquake

Question 32

Fluids in Faults

Answer 32

Will decrease friction that holds rock faces in place

Question 33

Discontinuities (Boundaries)

Answer 33

detected from refraction and reflection of body waves

Question 34

Moho

Answer 34

boundary between crust and mantle

Question 35

Oceanic Crust

Answer 35

8 km thick - Basalt then Gabbro

Question 36

Continental Crust

Answer 36

20-70 km thick - Granite then Diorite

Question 37

Mantle

Answer 37

Comprised of peridotite (rock made up of olivine and pyroxene)

Question 38

Core

Answer 38

P & S wave shadow zones indicate - outer core is liquid - composed of iron - inner core is solid