Lecture 5+6

Question 1

the Mercalli intensity scale

Answer 1

• method of measuring intensity of earthquakes
• based on observable earthquake damage
• not necessarily accurate (eyewitness accounts aren’t reliable)

Question 2

intensity

Answer 2

• measure of the effects of an earthquake on people and infrastructure

Question 3

magnitude

Answer 3

• amount of energy released during an earthquake

Question 4

shake map

Answer 4

• intensity map generated automatically in near - real time using data from seismograph stations
• input : ground motion data; knowledge of regional geology
• output: computed intensity

Question 5

frequency of different terrains

Answer 5

• soil = <1 Hz
• hard rock = >1Hz

Question 6

resonance

Answer 6

• a system experience a very large oscillations when it is disturbed by a forcing function of frequency equal to its natural frequency
• the energy of the forcing function is added to the system so that oscillations are reinforced
• oscillations grow bigger until the object breaks
• The oscillation caused by a seismic wave

Question 7

liquefaction

Answer 7

• the strength of soil is reduced by rapid and violent shaking or loading
• occurs in saturated soils in which the space between articles is filled with water
• low pore pressure = strong binding force
• high pore pressure = weak binding force

Question 8

elastic limit

Answer 8

• material exhibit elastic behavior
• beyond elastic limit there are two scenarios:
• material fails immediately
• plastic deformation

Question 9

flexibility of buildings

Answer 9

`- 10 Hz/ number of storeys

Question 10

resonance

Answer 10

• seismic waves act as forcing functions on foundation materials and buildings
• the building resonance is the number of seconds it takes for he building to naturally vibrate back and forth

Question 11

faults

Answer 11

• complex zones of breakage
• rough interlocking rocks

Question 12

fault rupture

Answer 12

• initiated at hypocenter
• the initiation of an earthquake

Question 13

slip fault

Answer 13

• displacement between the two rock blocks

Question 14

seismic waves

Answer 14

• caused by the release of energy in the earth

Question 15

amplitude

Answer 15

• max value measured from the equilibrium
• attuation: loss in amplitude as the wave propagates away from its source

Question 16

period

Answer 16

• time between two successive crests

Question 17

frequency

Answer 17

• number of waveforms in 1 second

Question 18

wavelength

Answer 18

• distance between two successive crests

Question 19

propagation

Answer 19

• velocity of propagation: v(m/s) = L(m/s)/T(s)

Question 20

seismometer

Answer 20

• sensor that detects ground motion

Question 21

seismograph

Answer 21

an instrument that record ground motion

Question 22

siesmogram

Answer 22

• paper record or digital file with data describing ground motion

Question 23

Zhang Heng

Answer 23

• first seismograph in china

Question 24

Body waves

Answer 24

• propagate through the whole body of the earth
• Large earthquakes generate body waves recorded all over the world

Question 25

P waves

Answer 25

• primary waves
• compressional energy
• small amplitude
• travel fastest: frist to be recorded
• faster in water slower in hard rock

Question 26

s waves

Answer 26

• secondary waves
• shear energy
• larger amplitude
• don’t travel as fast

Question 27

surface waves

Answer 27

• low frequency
• slow velocity
• very large amplitudes

Question 28

Richter magnitude scale

Answer 28

• difference between S and P wave arrival times
• max amplitude of body waves
• logarithmic scale (when the amplitude is multiplied by a factor of 10 the magnitude increases by +1