Lesson 13- What are the hazards associated with seismicity?

Question 1

Ground Shaking +Case study

Answer 1

• Ground shaking is brought by seuismic waves
• an area that shurken by waves (P and S) and surface can move a structure in an alternate way
• Mexico City suffered from an earthquake in 1985 where numerous structures crumbled and over 20,000 people lost their lives

Question 2

Ground displacement

Answer 2

• When the ground moves up, down, sideways to at least 10m
• Can cause distrubance of streets and utilities

Question 3

Earth rupture

Answer 3

• Delivers an issue scarp of up to a few metres of vertical uprooting
• This burst of the earth during a tremor may happen on auxiliary issues

Question 4

Avalanches and Landslides

Answer 4

• On soak inclines ans rocky territories, enormous tremors can set off numerous avalanches, rockfalls or torrential slides.

Question 5

Liquefaction

Answer 5

• When there is unconsolidated residue immersed in groundwater, the shaking provided by a seismic tremor may cause the dreg drains to lose contact with one another and become suspended in the water
  -transforms solid ground into fluid ground causing structures to sink, tilt or slide

Question 6

Fires

Answer 6

• The violent shaking can damage infrastructure such as gas lines and electrical networks. When these are severed or damaged, it can lead to gas leaks, which may ignite and cause fires.

Question 7

Tsunami + Case study

Answer 7

• A tsunami is a lot of waves in the sea with a very long wavelength, commonly more than 100km long. Torrents can be set off by seismic tremors that enormously shake the sea depths, which usually occurs at subduction zones.
• The tsunamis from the Sumatra seismic tremor of 2004 excecuted more than 100,000 individuals in seaside territories

Question 8

Can we predict earthquakes

Answer 8

• Dont currently posses the resoucres to accuratley predict earthquakes
• But well understood faults can be given approximate probabilities of earthquake ruptions

Question 9

Method of prediction- Precursors/foreshocks

Answer 9

• The Haicheng in 1975 earthquake produced foreshocks and the city was successfully evacuated
• However the Tnagshang earthquake in 1976 produced no foreshocks and killed 500,000

Question 10

Method of prediction- Radon gas

Answer 10

Small half life (3.5 days), only found shortly after its emitted
-increased radon gas could mean EQ

Question 11

Method of prediction-Ground water

Answer 11

• Levels of this in wells are known to dramitally change
  -noted as precursors in China and the USA

Question 12

Method of prediction- Remote sensing

Answer 12

• Changes in the earths crust from satalittes which measure change in electromagnetism; not accuratley predicting probabilities

Question 13

Methods of prediction- Electro-magnetism signals

Answer 13

• VAN method
• Tracks electric signals (better for small EQ’s)

Question 14

Method of Prediction-Seismic gap theory

Answer 14

• Area of a fault line that has’nt erupted in a long time
• Tried to prove this at Parkfield but didnt happen the way they expected

Question 15

Method of prediction- Fault line unzipping

Answer 15

• Used on Instabull to predict an earthquake along the North American fault.
• Measures the stress transfer along a faultline to predict where the next EQ will occur

Question 16

Is EQ prediction useful?

Answer 16

• Not very useful as no form of prediction method can tell us when or where specifically it will happen

Question 17

Preperation method- Tuned mass dampers

Answer 17

• Taipei-101
• A large concrete block mounted in the skyscraper which wave in the opposite direction

Question 18

Preperation method-Shock absorbers

Answer 18

• Springs with damper base designed to absorb the seismic shocks during the earthquake.

Question 19

Case studies of earthquake resistant buildings

Answer 19

• Istanbull Airport- can withstand a magnitude 8 airport and has isolating device that moves the entire building off of the ground
• Wellington Central Police Statiuon- The exterior walls have X-shaped bracing that enables the building to move as a rigid body. The building rests on 24 flexible piles, isolating it from the ground, and it has lead dampers to reduce shaking.