Lesson 3

Question 1

2 ways to measure earthquake size

Answer 1

1. Intensity
2. Magnitude

Question 2

is a non-instrumental perceptibility measure of damage to structures, ground surface effects (e.g. fractures, cracks and landslides) and human reactions to earthquake shaking.

Answer 2

Intensity

Question 3

it is a descriptive method which has been traditionally used to establish earthquake size, especially for pre-instrumental events.

Answer 3

Intensity

Question 4

the levels are represented by _______________ and each degree of intensity provides a qualitative description of earthquake effects.

Answer 4

Roman Numerals

Question 5

Most common intensity scales:

Answer 5

1. Mercalli-Cancani-Seiberg (MCS) - 12-level scale
2. Modified Mercalli (MM) - 12-level scale
3. Medvedev-Sponheuer-Karnik (MSK) - 12-level scale
4. European Macroseismic Scale (EMS) - 12-level scale
5. Japanese Meteoral Agency (JMA) - 7-level scale

Question 6

The first intensity scale

Answer 6

Rossi-Forel Scale

Question 7

______________ are usually obtained from interviews of observers after the event.

Answer 7

Earthquake intensities

Question 8

Intensity scales are used to plot contour lines of equal intensity or “isoseisms” “isoseismal” then generates an ____________.

Answer 8

Isoseismal Map

Question 9

provide approximate distributions of damage and the extent of ground shaking and shows how the intensity decreases, or attenuates, with increasing epicentral distance.

Answer 9

Intensity maps

Question 10

The intensity is generally greatest in the vicinity of the __________

Answer 10

Epicenter

Question 11

• is a quantitative measure of earthquake size and fault dimensions.
• based on the maximum amplitudes of body or surface seismic waves.
• an instrumental, quantitative and objective scale.

Answer 11

Magnitude

Question 12

The first attempt to define magnitude scales were made in _________ by _________ and in __________ by ___________ in the 1930s.

Answer 12

Japan-Wadati
California-Ritcher

Question 13

scales are ___________ because they measure amplitudes of seismic waves with different properties.

Answer 13

frequency-dependent

Question 14

Magnitudes are calculated from earthquakes recorded by an instrument called

Answer 14

seismograph

Question 15

Instruments that measure and record, as a function of time, motions of the ground, including those of seismic waves.

Answer 15

Seismometer/Seismographs

Question 16

Number of seismic stations in the Philippines (as of Dec. 2020)

Answer 16

108

Question 17

Seismograms can provide
information on

Answer 17

• epicenter location
• magnitude of earthquake
• source properties

Question 18

The most commonly used instruments for engineering purposes are strong motion

Answer 18

accelerographs/accelerometers

Question 19

These instruments record the acceleration time history of ground motion at a site, called an

Answer 19

accelerogram

Question 20

the resulting corrected acceleration record can be used by engineers to obtain __________ and ___________ by appropriate integration.

Answer 20

ground velocity and ground displacement

Question 21

Most common magnitudes scales:

Answer 21

i. Local (or Richter) magnitude(ML)
ii. Body wave magnitude (mb)
iii. Surface wave magnitude (MS)
iv. Moment magnitude (MW)

Question 22

In 1935, Charles Richter use a _______________________ to define a magnitude scale for shallow, local (epicentral distances less than about 600km (375miles) earthquakes in southern California

Answer 22

Wood-Anderson seismometer

Question 23

This scale is suitable for deep earthquakes that have few surface waves.

Answer 23

Body wave magnitude (mb)

Question 24

is a worldwide magnitude scale based on the amplitude of the first few cycles of P-waves which are not strongly influenced by the focal depth

Answer 24

Body wave magnitude (mb)

Question 25

is a measure of the amplitudes of LR-waves with a period of 20seconds, i.e. wavelength of about 60km, which are common for very distant earthquakes,

Answer 25

Surface wave magnitude (MS)

Question 26

accounts for the mechanism of shear that takes place at earthquake sources and not related to any wavelength.

Answer 26

Moment magnitude (MW)

Question 27

A phenomenon wherein as the total amount of energy released during an earthquake increases, however, the ground-shaking characteristics do not necessarily increase at the same rate.

Answer 27

Saturation