Earthquake hazard and mitigation

Question 1

What are 2 uses of the Global Seismograph Network?

Answer 1

Earthquake monitoring in seismogenic regions
Compliance with the Comprehensive Nuclear Test Ban Treaty

Question 2

What is an earthquake precursor?

Answer 2

A change that would indicate an earthquake were to occur

Question 3

Give some examples of earthquake and earthquake precursor monitoring devices

Answer 3

Seismometers- on and offshore
Tilt strain meters
Satellite radar interfermometry
Seafloor hydrosphere arrays
Ocean floor tsunami (pressure) guages

Question 4

Give some examples of earthquake precursors

Answer 4

Decrease in seismic velocity
Deformation: uplift, tilt, horizontal strain
Geomagnetic field variation
Level of seismic activity- foreshocks
Radon gas emission
Animal behaviour

Question 5

Why is earthquake prediction difficult?

Answer 5

The prediction system is complex due to there being so many different variables being involved

Question 6

What information is needed to predict an earthquake?

Answer 6

An understanding of stress cycles, strain transfer, seismic gaps, including geological earthquakes
To identify high-risk areas and produce risk assessments for them

Question 7

What is an example of a successful earthquake prediction?

Answer 7

Yingkow, China, 1975

Question 8

What is the aim of the Probabilistic Seismic Hazard Assessment?

Answer 8

To determine the probability that an area will experience earthquake-induced shaking, leading to some value of seismic intensity, over a defined time interval into the future

Question 9

What are the inputs of the probabilistic hazard assessment?

Answer 9

Regional scale tectonic setting
Seismicity records
Location of known faults

Question 10

What data was used to create the global seismic hazard map?

Answer 10

Earthquake catalogues
Potential earthquake sources
Ground motion records

Question 11

What % of the earth’s land is in the high/very high seismic range?

Answer 11

8%

Question 12

What % of the earth’s land surface is in the low hazard range?

Answer 12

70%

Question 13

What megacities lie within high or very high seismic range?

Answer 13

Kathamndu
Istanbul
Manila
Tokyo
Mexico City

Question 14

What 3 things do full assessments by authorities need to include?

Answer 14

Risk
Hazard
Vulnerability

Question 15

What is the definition of hazard?

Answer 15

Probability of ground shaking of a particular intensity or acceleration

Question 16

What is the definition of risk?

Answer 16

Probability of damage to people and building

Question 17

What is the definition of vulnerability?

Answer 17

How critical is the risk to the area e.g. assessing loss of life, injury or damage likely to be sustained

Question 18

What is the equation involving risk?

Answer 18

Risk = hazard x vulnerability

Question 19

What is liquefaction?

Answer 19

The process when water fills soft sediemnt when shaken, and allows the sediment to flow like a liquid

Question 20

What is the most important factor to consider when engineering buildings for earthquakes?

Answer 20

Cost vs risk

Question 21

What are most collpses caused by?

Answer 21

Horizontal shaking e.g. so buildings must be cross-braced

Question 22

What materials should be used to build appropriate buildings for earthquakes?

Answer 22

Steel and timber

Question 23

What is the biggest issue for future engineering of buildings for earthquakes?

Answer 23

Increasing global population, including increasing in cities increases future earthquake risk