Lesson 13- What are the hazards associated with seismicity? Flashcards
1
Q
Ground Shaking +Case study
A
- 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
2
Q
Ground displacement
A
- When the ground moves up, down, sideways to at least 10m
- Can cause distrubance of streets and utilities
3
Q
Earth rupture
A
- 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
4
Q
Avalanches and Landslides
A
- On soak inclines and rocky territories, enormous tremors can set off numerous avalanches, rockfalls or torrential slides.
5
Q
Liquefaction
A
- 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
6
Q
Fires
A
- 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.
7
Q
Tsunami + Case study
A
- 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
8
Q
Can we predict earthquakes
A
- Dont currently posses the resoucres to accuratley predict earthquakes
- But well understood faults can be given approximate probabilities of earthquake ruptions
9
Q
Method of prediction- Precursors/foreshocks
A
- 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
10
Q
Method of prediction- Radon gas
A
Small half life (3.5 days), only found shortly after its emitted
-increased radon gas could mean EQ
11
Q
Method of prediction-Ground water
A
- Levels of this in wells are known to dramitally change
-noted as precursors in China and the USA
12
Q
Method of prediction- Remote sensing
A
- Changes in the earths crust from satalittes which measure change in electromagnetism; not accuratley predicting probabilities
13
Q
Methods of prediction- Electro-magnetism signals
A
- VAN method
- Tracks electric signals (better for small EQ’s)
14
Q
Method of Prediction-Seismic gap theory
A
- 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
15
Q
Method of prediction- Fault line unzipping
A
- 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
16
Q
Is EQ prediction useful?
A
- Not very useful as no form of prediction method can tell us when or where specifically it will happen
17
Q
Preperation method- Tuned mass dampers
A
- Taipei-101
- A large concrete block mounted in the skyscraper which wave in the opposite direction
18
Q
Preperation method-Shock absorbers
A
- Springs with damper base designed to absorb the seismic shocks during the earthquake.
19
Q
Case studies of earthquake resistant buildings
A
- Istanbull Airport- can withstand a magnitude 8 earthquake and has isolating device that moves the entire building off of the ground
- Wellington Central Police Station- 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.
