Earthquakes - FACTORS OF GROUND SHAKING

Question 1

when was the Tangshan disaster and what magnitude was it?

Answer 1

1976 (Mm 7.5)

Question 2

what kind of earthquake was the Tangshan disaster?

Answer 2

intraplate earthquake

Question 3

why was the Tangshan disaster so destructive?

Answer 3

people have no memory of a large earthquake occurring in the area, therefore luling them into a false sense of security

Question 4

t or f: earthquakes don’t kill people buildings do

Answer 4

T

Question 5

it is the leading cause of death and property damage in most earthquakes

Answer 5

structural failure

Question 6

china earthquake when and how strong

Answer 6

2008, magnitude 7.9

Question 7

when engineers design a structure they take into account the fact that the structure must be able to withstand a range of _____, with _____ being the most important

Answer 7

different forces ; gravoty

Question 8

t or f: all structures have mass, at a bare minimum they must be strong enough to support their own weight against gravity

Answer 8

T

Question 9

gravity works in ____ direction, where structures are usually more resistant

Answer 9

vertical

Question 10

the lack of structural strength in the _____ direction becomes one of critical importance in areas where string earthquakes occur

Answer 10

horizontal / lateral

Question 11

the types of wave that is most destructive because of movement in lateral direction

Answer 11

surface waves

Question 12

buildings with crawl spaces or large open areas on the ground floor are inherently weak and prone to ______

Answer 12

cripple-wall failure

Question 13

the most dangerous types of homes are those constructed of

Answer 13

unreinforced masonry

Question 14

unreinforced masonry is when walls are usually constructed of brick bound together with mortar

Answer 14

T

Question 15

reinforced walls have internal support of _____ or _____

Answer 15

woods or steel

Question 16

this occurs when floors within a building become detached from the columns and fall in a cascading manner

Answer 16

pancaking

Question 17

mexico city earthquake

Answer 17

1985, magnitude 8.0

Question 18

concrete columns even if reinforced, can collapse when concrete reach their _____ and literally _____

Answer 18

elastic limit;
explode

Question 19

factors that affect ground shaking

Answer 19

period, natural vibration frequency, resonance;

focal depth and wave attenuation;

ground amplification

Question 20

the time (in seconds) it takes for a building to naturally vibrate back and forth

Answer 20

period

Question 21

t or f: smaller structures have higher period than larger structures

Answer 21

false (shorter period)

Question 22

period of ground motion is generally controlled by the ground’s _____

Answer 22

stiffness

Question 23

refers to the vibration of a structure at a fixed frequency

Answer 23

natural vibration frequency

Question 24

is the number of times the motion is repeated at a set amount of time

Answer 24

frequency

Question 25

t or f: as building height increases, the natural vibration frequency decreases

Answer 25

T

Question 26

what is resonance?

Answer 26

natural vibration frequency of a structure matches that of the seismic waves

Question 27

resonance occurs when _____ of the individual waves ______

Answer 27

amplitude ; combine

Question 28

what buildings are most susceptible to resonance?

Answer 28

10-20 stories high

Question 29

t or f: tall skyscrapers are unlikely to experience resonance

Answer 29

t

Question 30

energy of the resulting seismic waves steadily decreases as they travel away from the focus

Answer 30

wave attenuation

Question 31

the most dangerous earthquakes are those with a combination of

Answer 31

shallow focus and large magnitude

Question 32

t or f: it is possible for a relatively shallow, low-magnitude earthquake to generate greater ground motion than a deep, high magnitude earthquake

Answer 32

T

Question 33

seismic waves experience different amounts of wave attenuation depending on the ________

Answer 33

type of geologic materials they pass through

Question 34

loose materials and rocks with lower density will _______ from passing seismic waves

Answer 34

absorb more energy

Question 35

on areas of rigid rocks, seismic waves are able to ______ as they travel farther

Answer 35

retain more of their energy

Question 36

t or f: when waves undergo less attenuation, they therefore have the potential to cause damage farther from the focus

Answer 36

T

Question 37

new madrid earthquake series

Answer 37

magnitude 8, 1811-1812

Question 38

new madrid earthquake was able to retain energy to ring church bells in

Answer 38

Boston, Massachusetts

Question 39

when seismic waves travel through weaker materials, they _____ and ______ at a faster rate

Answer 39

slow down ; lose energy

Question 40

when waves travel through weaker material, they slow down causing the ______ to increase, creating a phenomenon called _____

Answer 40

wave amplitude ; ground amplification

Question 41

t or f: during ground amplification, weaker materials can begin to vibrate at the same frequency as that of seismic waves

Answer 41

T

Question 42

seismic waves entering a basin would amplify because they are ________ in the sedimentary material

Answer 42

forced to slow down

Question 43

t or f: areas undergoing ground amplification may have an extended duration of ground shaking

Answer 43

T

Question 44

seismic waves in sedimentary basin can become trapped and undergo ______ creating a ________ effect

Answer 44

internal reflection ; reverberating effect

Question 45

the ____ shape of a basin can cause waves to _____ and _____, focusing their energy into localized areas which then experience more intense shaking

Answer 45

convex ; refract and merge