Midterm #1-Chapter 3

Question 1

fracture

Answer 1

a general term for any breaks in rock

Question 2

mainshock

Answer 2

largest EQ in a sequence

Question 3

foreshock

Answer 3

smaller EQ that precedes mainshock (on the same sectipn of a fault)

Question 4

aftershock

Answer 4

smaller EQs following a mainshock- can continue for years following the mainshock

Question 5

seismology

Answer 5

study of EQs and the earth’s interior

Question 6

seism

Answer 6

an EQ

Question 7

arrival time

Answer 7

time when an EQ is detected by a seismograph

Question 8

seismometers

Answer 8

instruments that detect earth’s motions

Question 9

inertia

Answer 9

that property by which matter will remain at rest unless acted on by an external force

Question 10

seismograms

Answer 10

records made by seismographs

Question 11

wavelength

Answer 11

distance between two successive waves

Question 12

period

Answer 12

the length of time for a complete cycle of waves to pass

Question 13

hertz (Hz)

Answer 13

unit of frequency. One hertz equals one cycle per second

Question 14

amplitude

Answer 14

maximum displacement above or below the undisturbed position (the height of a wave crest)

Question 15

natural frequency

Answer 15

frequency at which a mechanical system (soil, a building) vibrates when disturbed

Question 16

resonance

Answer 16

phenomenon when vibrations grow larger and larger

Question 17

when earth shakes, it releases ____ that pass through the body of the planet

Answer 17

seismic waves

Question 18

two types of seismic waves

Answer 18

body waves and surface waves

Question 19

body waves

Answer 19

includes P (primary) and S (secondary waves)

Question 20

surface waves

Answer 20

includes L (love waves) and R (rayleigh waves)

Question 21

fastest waves are the

Answer 21

P waves

Question 22

slowest waves are the

Answer 22

L waves

Question 23

P waves

Answer 23

pass through solids, liquids, and gas, move in a pull-push motion

Question 24

S waves

Answer 24

only pass through solids, move in a shearing motion

Question 25

R waves

Answer 25

move in a backward rotating, elliptical motion (rocking boat motion)

Question 26

L waves

Answer 26

move in a side-side, horizontal plane motion (similar motion to S waves)

Question 27

isoseismal maps

Answer 27

map that shows the effects of the same EQ in different areas - demonstrating the different intensities

Question 28

felt area

Answer 28

surface over which the EQ was felt by people

Question 29

liquefaction

Answer 29

when strong EQ shaking causes solid sediments to transform into liquid

Question 30

when soils are saturated...

Answer 30

soils loose strength and stiffness, which weakens their ability to withstand and support heavy loads

Question 31

soft sediments vibrate at ____ frequencies

Answer 31

lower

Question 32

hard sediments vibrate at ______ frequencies

Answer 32

higher

Question 33

the greatest earthquakes in the world will occur where...

Answer 33

plate collide (convergent zones)

Question 34

megathrust EQs

Answer 34

occurs when stress accumulates at subduction - dominated by shear stress... typically happen within 30 kms of the crust (shallow)

Question 35

seismic gap method

Answer 35

theory that suggests EQs are expected next along the fault segments that have not moved for the longest time

Question 36

world's most famous fault:

Answer 36

San Andreas Fault (located offshore of San Fransisco)

Question 37

locked zone

Answer 37

section of a fault that has not released seismic energy in a long time

Question 38

creeping zone

Answer 38

section of a fault where energy is released frequently creating small to moderate EQs

Question 39

what must designs for buildings in "EQ country" account for?

Answer 39

acceleration (the rate of change of motion)

Question 40

the higher the magnitude of an EQ, the higher the ___

Answer 40

acceleration

Question 41

retrofitting

Answer 41

strengthening pre-existing buildings (bracing it, infilling walls, adding frames to the interior or exterior, isolating it off the ground)

Question 42

what scale are EQ's effect on people and buildings assessed on?

Answer 42

the Mercali Intensity scale