Natural Hazards

Question 1

Palaeoseismology

Answer 1

estimate earthquake through ancient patterns of area look at laid down deposits

Question 2

Seismic gaps

Answer 2

is a segment of an active fault known to produce significant earthquakes that has not slipped in an unusually long time, compared with other segments along the same structure.

Question 3

Short Term precursors

Answer 3

• ground uplift and tilting

- foreshocks

Question 4

Water levels in wells

Answer 4

opening cracks may force water to rise or fall

Question 5

Emission of radon gas

Answer 5

cracks may allow radon to escape (from granites)

Question 6

Changes in electrical resistivity of rocks

Answer 6

rocks are poor conductors but if small cracks develop and are filled with water then resistivity will decrease

Question 7

Unusual radio waves

Answer 7

observed but no clear explanation

Question 8

Strange animal behaviour

Answer 8

possibly detecting p-waves or foreshocks

Question 9

Tsunami Warning System (TWS)

Answer 9

• Pacific tsunami warning system
• 26 member states
• monitor tidal gauge heights and seismometer readings
• warnings issued (TV/Radio, Sirens/Loudspeaker, WWW)
• evacuation plant publicised and rehearsed

Question 10

Earthquake resistant buildings

Answer 10

• shock absorbers base isolation bearings to stop shaking of building
• strong column, weak bean design
• cross bracing reinforce walls
• shear walls (concrete walls with steel bars) to reduce rocking movement