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Earthquake-Prelims > Module 1&2 > Flashcards

Module 1&2 Flashcards

1
Q

study of the
generation, propagation and measurement of seismic waves through earth and the sources that
generate them.

A

Seismology

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2
Q

The word seismology originated from Greek words,

A

‘seismos’ meaning
earthquake and ‘logos’ meaning science.

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3
Q

earth’s shape is an oblate
spheroid with a diameter along the equator of
about

A

12740 km

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4
Q

polar diameter as

A

12700km.

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5
Q

The higher diameter along equator
is caused by the

A

higher centrifugal forces
generated along the equator due to rotation
of earth

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6
Q

pecific gravity of
materials that constitute the surface of earth
is only about

A

2.8,

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7
Q

e average specific gravity
of earth is about

A

5.5

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8
Q

very heavy materials towards interior of earth.
The interior of the earth can be classified into
three major categories

A

Crust, Mantle and
Core

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9
Q

or the lithosphere, is the outer part of the earth is where the life exist. The
average thickness of crust beneath continents is about 40km where as it decreases to as much
as 5km beneath oceans. The oceanic crust is constituted by basaltic rocks and continental part
by granitic rocks overlying the basaltic rocks. Compared to the layers below, this layer has high
rigidity and anisotrop

A

Crust

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10
Q

e is a 2900 km thick layer. The mantle consists of 1) Upper Mantle reaching a
depth of about 400 km made of olivine and pyroxene and 2) Lower Mantle made of more
homogeneous mass of magnesium and iron oxide and quartz. No earthquakes are recorded in
the lower mantle. The specific gravity of mantle is about 5. The mantle has an average
temperature of about 2200degree Celsius and the material is in a viscous semi molten state.
The mantle act like fluid in response to slowly acting stresses and creeps under slow loads. But
it behaves like as solid in presence of rapidly acting stresses, e.g. that caused by earthquake
waves.

A

Mantle

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11
Q

has a radius of 3470 km and consists of an inner core of radius 1370 km and an
outer core (1370 km < R < 3470 km). The core is composed of molten iron, probably mixed
with small quantities of other elements such as nickel and sulfur or silicon. The inner solid core
is very dense nickel-iron material and is subjected to very high pressures. The maximum
temperature in the core is estimated to be about 3000 degree Celsius. The specific gravity of
outer core is about 9-12 where as that of inner core is 15.

A

Core

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12
Q

proposed the hypothesis that the continents
had once formed a single landmass before breaking apart and drifting to their present locations.

A

German scientist Alfred Wegener, in 1915

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13
Q

He proposed that a large
continent termed Pangae existed in earth around

A

200 million years ago

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14
Q

The theory of plate tectonics, presented in early

A

y 1960s

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15
Q

lithosphere is
broken into seven large (and several smaller) segments called

A

plates

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16
Q

The upper rigid layer,

A

lithosphere

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17
Q

, is about 100 km
thick below the continents, and about 50 km under the oceans, and consists of Crust and rigid
upper-mantle rocks.

A

lithosphere

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18
Q

The lower layer

A

asthenosphere

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19
Q

extends down to about 700 km
depth.

A

asthenosphere

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20
Q

are areas along the edges of plates move
apart from each other

A

Spreading ridges or divergent boundaries

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21
Q

are located beneath the
oceans

A

spreading ridges

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22
Q

are formed where the two plates move toward each other.
In this process, one plate could slip below the other one or both could collide with each other.

A

convergent boundaries

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23
Q

These boundaries are created when either oceanic lithosphere subducts beneath oceanic
lithosphere (ocean-ocean convergence), or when oceanic lithosphere subducts beneath
continental lithosphere (ocean-continent convergence)

A

Subduction boundaries

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24
Q

The junction where the two
plates meet, a trench known as

A

oceanic trench

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25
Q

When two plates with continental lithosphere collide, subduction ceases and a mountain
range is formed by squeezing together and uplifting the continental crust on both plates

A

Collision Boundaries

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26
Q

occur along the plate margins where two plate moves past each
other without destroying or creating new crust,

A

Transform boundaries

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27
Q

is used to describe a discontinuity within rock mass, along which
movement had happened in the past

A

fault

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28
Q

are
mappable linear surface features and may reflect subsurface phenomena

A

Lineaments

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29
Q

Types of faults

A

Normal Fault
Reverse fault
Strike-slip fault
Oblique Fault

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30
Q

There are two important parameters associated with describing faults

A

dip and
strike

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31
Q

is the direction of a horizontal line on the surface of the fault

A

strike

32
Q

measured in a vertical plane at right angles to the strike of the fault

A

dip

33
Q

refers to the upper rock surface along which
displacement has occurred

A

hanging wall of a fault

34
Q

The vertical
shift along a fault plane is called the

A

throw

35
Q

horizontal displacement is termed as

A

heave

36
Q

the slippage
occurred along the dip of the fault

A

dip-slip fault

37
Q

the
movement has taken place along the strike

A

strike-slip fault

38
Q

The movement occurs diagonally
across the fault plane in case of an

A

oblique slip fault

39
Q

Based on relative
movement of the hanging and foot walls faults are classified into

A

normal, reverse and wrench
faults

40
Q

the hanging wall has been displaced downward relative to the footwall

A

normal fault

41
Q

the hanging wall has been displaced upward relative to the
footwall,

A

reverse fault

42
Q

the foot or the hanging wall do not move up or
down in relation to one another

A

wrench fault

43
Q

which are a subdivision of
reverse faults, tend to cause severe earthquakes.

A

Thrust faults

44
Q

are nucleating surfaces for seismic activity

A

Faults

45
Q

The region on the fault, where rupture initiates is known as the

A

e focus or hypocenter of
an earthquake

46
Q

is the location on the earth surface vertically above the focus.

A

Epicenter

47
Q

Distance from epicenter to any place of interest is called the

A

epicentral distance

48
Q

The depth of
the focus from the epicenter is the

A

focal depth

49
Q

e is the vibration of earth’s surface caused by waves coming from a source of
disturbance inside the earth

A

Earthquake

50
Q

arriving at a site on the surface of the earth are a result of
complex superposition giving rise to irregular motion.

A

seismic waves

51
Q

These waves propagate by longitudinal or compressive action, which mean that the
ground is alternately compressed and dilated in the direction of propagation

A

primary waves, push-pull waves, longitudinal waves

52
Q

are the fastest among the seismic waves and travel as fast as 8 to 13 km per second.

A

P
waves

53
Q

these are the first waves to reach any seismic station
and hence the first to be
recorded.

A

P
waves

54
Q

These are transverse or shear waves, which mean that
the ground is displaced perpendicularly to the direction of propagation

A

​
shear waves, secondary waves, transverse waves

55
Q

These waves are capable of
traveling only through solids

A

Secondary (S) Waves

56
Q

They travel at the rate of 5 to 7 km per second. For this reason these waves are always
recorded after P waves in a seismic station.

A

Secondary (S) Waves

57
Q

When the vibratory wave energy is propagating near the surface of the earth rather
than deep in the interior

A

Surface Waves

58
Q

wo other types of surface waves

A

Rayleigh and Love waves

59
Q

their journey is confined to the surface
layers of the earth only

A

Surface Waves

60
Q

s travel through the earth crust and does not propagate
into the interior of earth

A

Surface Waves

61
Q

are the slowest among the seismic waves

A

Surface Waves

62
Q

They travel at
the rate of 4 to 5 km per second

A

Surface Waves

63
Q

hese waves are capable of travelling through solids and liquids

A

Surface Waves

64
Q

are tension-compression waves similar to the P-waves
expect that their amplitude diminishes with distance below the surface of the ground

A

Rayleigh surface waves

65
Q

are the counterpart of the “S” body waves

A

Love waves

66
Q

Generally, the rupture causing earthquakes initiates from a point, termed

A

hypocenter
or focus

67
Q

The point on
earth’s surface diametrically opposite to the epicenter is called the

A

anti-center

68
Q

An imaginary
line which joins the points at which the earthquake waves have arrived at the earth’s surface at
the same time is called a

A

‘co-seismal’

69
Q

The seismograph has three components

A

the sensor, the recorder and the timer

70
Q

The instruments measure the ground displacements and are called

A

seismographs

71
Q

The
record obtained from a seismograph is called a

A

seismogram

72
Q

e devises that measure the ground accelerations are called

A

accelerometer

73
Q

e refers to the degree of destruction caused by it

A

intensity

74
Q

An imaginary line joining the points of same intensity of the earthquake is called an

A

iso-seismal

75
Q

related to the amount of energy released by the
geological rupture causing it, and is therefore a measure of the absolute size of the earthquake,
without reference to distance from the epicenter

A

magnitude of an earthquake

76
Q
A

Earthquake-Prelims (3 decks)

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