EQ Hazard and Mitigation

Question 1

EQ precursors

Answer 1

Decrease in seismic velocity
Deformation
Geomagnetic field varitations
Foreshocks
Groundwater flow
Radon Gas emissions
Animal behaviour

Question 2

pore fluid in the brittle crust

Answer 2

reduces fracture strength of rocks and stress needed to break them

Question 3

Effective pressure/stress

Answer 3

= lithostatic pressure - pre fluid pressure

Question 4

Man made fluid changes

Answer 4

filling reservoirs, water into boreholes

Question 5

Stress increase in EQ build up

Answer 5

small fractures, more space for pore water, pore water pressure may drop before an EQ

Question 6

Fluid examples

Answer 6

Aswan high dam, egypt. sandstones

Question 7

Probabilistic Seismic Hazard Assessment

Answer 7

regional tectonics, current seismic info, intensity levels, patterns, location of know faults and slips,
OUTPUT: EQ hazard zoning

Question 8

Accelarartions exceeding 0.25g have a 50% prob of occurring here in 30 years

Answer 8

Eg of PSHA

Question 9

Global seismic hazard map

Answer 9

from earthquake catalogues, potential EQ sources, 8% of earth in high seismic range
70% low hazard

Question 10

Seismic hazard in california

Answer 10

probability of ground shaking exceeding 0.2g in next 50 years

Question 11

Hazard

Answer 11

Prob of ground shaking of a particular intensity or acceleration

Question 12

Risk

Answer 12

probability of damage to people and buildings

Question 13

Vulnerability

Answer 13

criticality of risk, effects and benefits of mitigation

Question 14

Risk =

Answer 14

Hazard x Vuln

Question 15

Secondary hazards

Answer 15

Ground conditions
Liquefaction
Mudlsides, landslides,
Tsunamis

Question 16

Anthropogenic factors

Answer 16

Building construction, pop density, dams/nuclear etc, communcation roads e.g. bridges, education and preparation, gas/fire potential

Question 17

Soft sediments vs. bedrock

Answer 17

amplicates seismic waves in soft low density sediments

Focussing of seismic waves by refraction; amplitude increases

Question 18

Liquefaction

Answer 18

soft sediments with high water content:
lose bong, sediments beome saturated and lose strength
reduced ground stability

Question 19

Engineering buildings

Answer 19

minimal cost protection, withstand shaking
cross braced
flexibility
resonant freq in materials

Question 20

masonry

Answer 20

add steel

Question 21

future EQ risk

Answer 21

1/3 of 27 big cites near plate boundaries

high likelihood of catastrophic fatalities