Lecture 1: Earthquakes

Question 1

Earthquake scales- Eq intensity

Answer 1

measure of the shaking created by the earthquake- value varies w location- indicates damage

Question 2

Earthquake scales- EQ magnitude

Answer 2

a measured value of the EQ size- energy released- ground motion- at set number of km- area of fault

Question 3

Richter magnitude scale

Answer 3

using amplitude of seismic waves- corrected for distance from the focus

takes seconds to calculate- less accurate

Question 4

moment magnitude scale

Answer 4

measure of energy release, calculated from area- slip and rock strength

takes hours to calculate- ore accurate

Question 5

models for EQ- prediction

Answer 5

all eq-

characteristic m- will be same size and occur with reg periodicity

probabilistic- based on historical obvs

slip predictable m and time- know the time of last eq- estimate size of next- by reaccumulation of strain

Question 6

short term prediction

Answer 6

p waves arrive quicker- more damaging then s waves- high amplitude shaking

radio waves- much faster also

very rapid warnings- disseminated to railways power and gas companies and hospitals

Question 7

secondary hazards

Answer 7

liquefaction- loose weakly compacted sediment soil- causes buildings to collapse and buckled roads

tsunamis- fire- aftershocks- landslides- infrasture damage

resonant natural freq- atoms are in constant vibration- rate at which structure likes to vibrate

Question 8

eq - human induced

Answer 8

yes- monticello reservoir- south carolina- first 6 monts- 1000 seismic events

rocky mountain arsenal- waste injection triggered eq

Question 9

moonquakes

Answer 9

yes- happen less freq- smaller magnitudes- than earth eq

appear to be released to tidal stresses - associated w varying differences between earth and moon

occur at great depth- halfway btw surface and centre of moon

Question 10

no thing as Eq weather

Answer 10

equal distribution- of eq in all weather

no physical way weather could affect forces beneath earths surface

the fact of barometric pressure doesn’t reach beneath the soil

Question 11

before electronics

Answer 11

spring pendulum - 15 tons