Earthquakes - METHODS OF ASSESSING EARTHQUAKES

Question 1

three methods of assessing earthquakes

Answer 1

long-term forecasting
short-term prediction
other methods (gephysical)

Question 2

based mainly on the knowledge of when and where earthquakes have occurred in the past

Answer 2

long-term forecasting

Question 3

long term forecasting are based on ______ and _____

Answer 3

historical records and geologic evidences

Question 4

t or f: in seismically active areas, large earthquakes are more likely to occur as the amount of time increases since the last major event

Answer 4

T

Question 5

two important aspects of long-term forecasting

Answer 5

paleoseismology
seismic gaps

Question 6

study of prehistoric earthquakes

Answer 6

paleoseismology

Question 7

what is paleoseismology

Answer 7

study of prehistoric earthquakes by studying offsets in sedimentary layers near fault zones and looking into materials that can be dated

Question 8

materials that can be dated in paleoseismology

Answer 8

coal seams, peat

Question 9

paleoseismology determines

Answer 9

recurrence intervals of major earthquakes prior to historical records

Question 10

paleoseismology is done thru:

Answer 10

trenching

Question 11

depth of trenching:
width of trenching:

Answer 11

2m;
depends on the fault

Question 12

formation of sand blows is linked to

Answer 12

liquefaction

Question 13

sand and water that come out onto the ground surface during an earthquake as a result of liquefaction

Answer 13

sand blows

Question 14

what type of dating are used in sand blows to determine earthquake event?

Answer 14

radiocarbon dating

Question 15

a zone along a tectonically active area where no earthquakes have occurred recently but is said to be still accumulating strain

Answer 15

seismic gaps

Question 16

it was known as a gap before the september 15, 1985 earthquake

Answer 16

Former Michoacan Gap

Question 17

two gaps along the cocos plate and acapuclo trench

Answer 17

Former Michoacan Gap and Guerrero gap

Question 18

involves monitoring of processes that occur in the vicinity of earthquake prone faults that may signify a coming earthquake

Answer 18

short-term prediction

Question 19

anomalous events or processes that may precede an earthquake

Answer 19

precursor events

Question 20

successful short term prediction have been difficult to obtain because:

Answer 20

earthquakes are generated deep beneath the surface and are difficult to monitor

Question 21

t or f: no consistent patterns for short-term prediction have been recognized because earthquakes in different region or faults all behave differently

Answer 21

T

Question 22

earthquakes precursors

Answer 22

1. increased foreshocks
2. slight swelling/uplift or tilting of ground surface
3. decreases electrical resistance
4. fluctuating water level in wells
5. increased radon concentration in groundwater
6. generation of radio signals

Question 23

these form prior to complete rupture

Answer 23

microcracks

Question 24

t or f: microcracks decrease the volume of rocks

Answer 24

F (increase)

Question 25

water entering void spaces results in a _____ in electrical resistance

Answer 25

decrease

Question 26

water entering new cracks causes water in well to ______; and will ______ when voids are closed again

Answer 26

lower ; rise again

Question 27

t or f: radon is an inert gas, meaning it is non-reactive

Answer 27

T

Question 28

radon is a radioactive decay product of ____

Answer 28

uranium

Question 29

radon escape from ____ and enter ____-

Answer 29

rocks ; wells

Question 30

radio signals are caused by

Answer 30

changes in rock strain;
movement of saline groundwater

Question 31

advantages of non-conventional / alternative geophysical surveys

Answer 31

non-intrusive;
sensors are planted on the ground;
utilizes passive sources;
cost-effective
cover wide area and up to 3km deep
fast and efficient, 4 hrs max

Question 32

examples of passive sources

Answer 32

ambient noise, microtremors

Question 33

three types of non-conventional methods

Answer 33

microtremor survey method
refraction microtremor survey
horizontal-to-vertical spectral ratio method

Question 34

microtremor survey method uses

Answer 34

7 portable seismometers

Question 35

each instrument in microtremor survey method is equipped with ______ for _____ and _______

Answer 35

Global Positioning System ;
time synchronization and location coordinates

Question 36

microtremor surveys records

Answer 36

microtremors for a few minutes

Question 37

a hammer striking a steel plate is used as a seismic source

Answer 37

refraction microtremor survey

Question 38

in refraction microtremor survey, a series of _____ are planted on the ground and connected to _______

Answer 38

geophones ; seismograph

Question 39

in refraction microtremor surveys, ________ were measured and analyzed

Answer 39

propagating waves

Question 40

uses the same instrument as microtremor survey method but only a single station

Answer 40

horizontal-to-vertical spectral ratio method

Question 41

what does horizontal-to-vertical spectral ratio method record?

Answer 41

ground period of an area

Question 42

recording time required for horizontal-to-vertical spectral ratio method

Answer 42

20 mins at most

Question 43

reducing earthquakes risk (4)

Answer 43

1. structural engineering
2. early warning systems
3. planning and education
4. earthquake control?

Question 44

seismic engineering provide greater structural strength with respect to the ____ generated by ______ and structure’s own ________

Answer 44

shear forces ; lateral ground motion ; inertia

Question 45

seismic engineering methods

Answer 45

shear walls
cross bracing
base isolation
steel jacket
steel jacket wrapped spirally

Question 46

a somewhat expensive but viable option to make existing buildings resistant to lateral movement is to _____

Answer 46

retrofit existing buildings with seismic controls

Question 47

the basic idea behind an early warning system is to take advantage of the ______ and the fact that

Answer 47

time lag ; P waves do very little damage

Question 48

the first ______ is simply used as an alert that a highly destructive _____ and ______ will follow soon

Answer 48

P-waves ; S waves ; surface waves

Question 49

examples of early warning systems

Answer 49

close valves on gas lines
shut down electrical powers
trains stopped

Question 50

planning and education for earthquake includes:

Answer 50

hazard assessment
development of building codes
informing people on what to do before, during and after
regular earthquake drills

Question 51

examples of human induced eartquakes

Answer 51

1. hoover dam blocked colorado river generated 600 earthquakes , one with mag 5 and 2 with mag 4
2. injection of toxic waste in disposal wells, generated earthquake 4-8 km below 3.8 km well
3. underground nuclear testing generated 6.3 magnitude earthquake, aftershock was mag 5