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GEOHAZARD > EARTHQUAKE > Flashcards

EARTHQUAKE Flashcards

1
Q

For rocks to be deformed, they must be acted upon by stress
which can be classified into three (3) basic types; what are the 3 basic types?

A

Compression, Tension, Shear

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2
Q

pushes on rocks from opposite
directions which causes rocks to be shortened parallel to the stress applied

A

Compression

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3
Q

pulls rocks from opposite directions, resulting it to become stretched/lengthened

A

Tension

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4
Q

occurs when rocks are being pushed in an uneven manner, causing the rocks to be skewed
such that different sides of a rock body slide or move in opposite directions

A

shear

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5
Q

true or false? rock near the surface of the earth are elastic?

A

true

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6
Q

what is rock elasticity?

A

when a force
(stress) that is acting on
them is removed, the
rocks will return to their
original shape

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7
Q

what is elastic limit?

A

the point in which they no longer behave elastically and deformation becomes permanent

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8
Q

when rocks deform they often slide past one another along a fracture plane, the fracture is called?

A

fault

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9
Q

refer to vibrational waves that travel through solid earth
materials which may be magmatic, tectonic, or artificial in origin.

A

seismic waves

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10
Q

what are the two types of seismic waves? differentiate.

A

Body waves; travel trough the earth’s interior, spreading
outward from the hypocenter in all directions and surface waves; travel on the earth’s surface away from the
epicenter (like ripples on water); slowest wave

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11
Q

compressional waves; parallel
to direction the wave is travelling, causing rocks to
alternately compress and decompress as successive
waves pass through.

A

primary waves

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12
Q

type of body wave that transverse/ perpendicular
to direction of wave propagation

A

secondary wave

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13
Q

also known as ground roll, spread to the ground as ripples, similar to rolling waves on the ocean; move both vertically and horizontally in
a vertical plane pointed in the direction in which the
wave is travelling;

A

rayleigh waves

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14
Q

move the ground from side to side in a horizontal plane but at right angles to the direction
of propagation

A

love wave

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15
Q

the instrument used to detect
seismic waves

A

seismometer

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16
Q

a seismometer with a recording device that
produces a permanent record of earth motion, usually in the
form of wiggly line drawn on a moving strip of paper

A

seismograph

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17
Q

the paper record of earth vibration

A

seismogram

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18
Q

how do they locate earthquakes

A
  1. P and S waves start out from the hypocenter.
  2. As they travel, they gradually separate because of
    their different speeds.
  3. The interval of the time of arrival between P and S
    waves increases with increasing distance of the
    seismic stations from the focus and epicenter; the
    longer the time, the greater the distance is.
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19
Q

true or false? The interval of arrival between S and P waves is used to calculate the distance of the seismograph station from the earthquake source.

A

true

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20
Q

how deep is shallow, intermediate and deep in classifying earthquakes?

A
  1. Shallow – 0.70 km
  2. Intermediate – 70-350 km
  3. Deep – 350-670 km
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21
Q

How were the major layers of Earth inferred?

A

through seismic method

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22
Q

when rocks are subjected under a force, also called
_____, they can become deformed and have a
corresponding change in their shape (distortion) or
volume (dilation), a process known as ______.

A

stress; strain

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23
Q

two types of earthquake? explain how this occur.

A

volcanic and tectonic earthquake

24
Q

Based on the relationship between stress and strain
and the deformation of rocks, earth scientists have developed the ________________ that explains the occurrence of earthquakes.

A

elastic rebound theory

25
Q

vibrational wave energy that
radiates outward and causes the ground to shake in
what is called an _____

A

earthquake

26
Q

The release of energy generally begins at a point
called the focus/hypocenter whereas the point on
the earth’s surface directly above the hypocenter is
termed as _____

A

epicenter

27
Q

This redistribution of strain
commonly produces a series of smaller earthquakes called ________, which may continue to occur for days or weeks after the primary earthquake, sometimes called the _____

A

aftershocks; main shock

28
Q

In areas where tensional forces dominate the friction along faults is naturally low, allowing them to slip in an almost continuous process known as _________

A

fault creep.

29
Q

It is often referred to as a _______ due to the network of interlocking faults located on either side.

A

fault zone

30
Q

earthquake that forms when an oceanic plate is overridden by another plate

A

subduction zone earthquakes

31
Q

Factors that affect Ground Shaking

A
  • period, Natural Vibration Frequency, and
    Resonance
  • Focal Depth and Wave Attenuation
  • Ground Amplification
32
Q

true or false “Smaller structure take shorter time to vibrate back and forth than larger structures”

A

true

33
Q

Natural Vibration Frequency

A

refers to the vibration of a structure/building at a fixed
frequency; frequency is the number of times the motion is
repeated in a set amount of time.

34
Q

The matching of frequency then leads to the phenomenon called _______, whereby the amplitudes of the individual waves combine

A

resonance

35
Q

energy of the resulting seismic waves steadily decreases as they travel away from the focus, a process referred to as
________.

A

wave attenuation

36
Q

what is ground amplification

A

When seismic waves
travel through weaker
materials, they slow down and
lose energy at a faster rate.
This, in turn, causes wave
amplitude to increase, creating
a phenomenon known as
ground amplification.

37
Q

name secondary earthquake hazards

A

liquefaction
ground displacement
ground fissures
earthquake-induced mass wasting
fires
tsunamis

38
Q

Who is the Italian seismologist who developed a means of comparing both modern and historical earthquakes through the use of firsthand human observations during
earthquakes? what is this called?

A

Giuseppe Mercalli; Mercalli Intensity scale

39
Q

is a seismic scale used and developed by the Philippine Institute of Volcanology and Seismology (PHIVOLCS) to measure the intensity of an earthquake.

A

PHILIPPINE EARTHQUAKE INTENSITY SCALE (PEIS)

40
Q

Intensity scale ranges from ______.

A

I to X

41
Q

they quantify the amount of ground motion during an earthquake and the energy that was released when the rocks ruptured.

A

Magnitude scales

42
Q

Differentiate Moment Magnitude scale and Ritcher Magnitude scale?

A

Richter Scale is mostly effective for regional earthquakes no greater than M5. Moment Magnitude is more effective for large earthquakes Moment Magnitude uses more variables to calculate the energy released using seismic moment. Seismic moment combines the seismic energy with offset on the fault and rigidity of rock.

43
Q

what are the classes of earthquakes based on their magnitude?

A

Great - 8 or more
Major - 7.0-7.9
Strong - 6.0-6.9
Moderate 5.0-5.9
Light - 4.0-4.9
Minor 2.0-3.9
Microearthquake 1.0-1.9

44
Q

A Method of assessing earthquake where it is based mainly on the knowledge of
when and where earthquakes occurred in the past

A

long-term forecasting

45
Q

study of prehistoric earthquakes

A

paleoseismology

46
Q

a zone along a tectonically
active area where no
earthquakes have occurred
recently, but it is known that
elastic strain is building in
the rocks.

A

seismic gap

47
Q

involves monitoring of processes
that occur in the vicinity of earthquake prone faults for activity that signify a coming earthquake.

A

short-term prediction

48
Q

Anomalous events or processes that may precede an earthquake are called _________and might signal a coming earthquake

A

precursor events

49
Q

Earthquake precursors

A
  1. increase in foreshocks
  2. slight swelling/uplift or tilting of the ground surface
  3. decreases electrical resistance
  4. Fluctuating water levels in wells
  5. increased concentration if radon gas in groundwater
  6. generation of radio signals
50
Q

3 examples of non-conventional / intrusive methods

A
  1. Microtremor survey method
  2. Refraction Microtremor Method
  3. Horizontal-to-Vertical Spectral Ration Method
51
Q

Reducing Earthquake Risks

A

Seismic engineering
Early warning systems
planning and education
earthquake control?

52
Q

How long is the Philippine Fault?

A

1200-1250 km

53
Q

Thrust Fault vs Reverse Fault

A
  • Thrust Fault
    o usually less than 45 degrees
    o PHIVOLCS - <30o
  • Reverse Fault
    o Steeper
    ▪ >45/30o
54
Q
  • a planar zone of seismicity corresponding with the down-going slab in a subduction zone
A

Wadati–Benioff zone

55
Q
A

GEOHAZARD (3 decks)

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