Lecture 3- Earthquake Intensity And Hazard Flashcards
What is ground acceleration?
The rate of change fo ground acceleration in an earthquake event
Where does most damage from ground acceleration occur?
In the horizontal plane
What is PGA?
Peak ground acceleration- the maximum acceleration of the ground during an earthquake event
What is the smaller PGA value for a “felt” earthquake?
0.001g
What is the smallest PGA value to cause damage to weak buildings?
0.05g
What is the PGA value typically associated with large earthquakes?
> 1.0g
What are the 9 factors that influence earthquake damage (besides ground acceleration)
- Duration of shaking
- Type of building (eg. Height, material)
- Frequency of ground oscillations
- Bedrock
- Direct surface fault breakage
- Landslides
- Liquefaction
- Fires
- Floods
Which frequency of shaking causes the most damage to tall buildings?
Low frequency
What does frequency of seismic waves interfere with?
Resonant frequency
How many people died in the 1970 Mt. Huscavaran earthquake?
6000 people
Give an example of a famous liquefaction event
Port royals, Jamaica, 1962. Magnitude 8 earthquake causes 1/3 of the two not disappear under the sea and 2500 resident deaths
Give four examples of earthquake related fire events
- Sean Francisco 1906
- Tokyo 1923
- Managua 1972
- Kobe 1995
What happened in San Fernando in 1971?
80000 people were evacuated on a flood risk from the van Norman dam damn
What does earthquake intensity describe?
The severity of shaking with a numerical scale
What is EMS-98 and where is it used?
The European Macroseismic scale, used in europe
What is the MMI56 and where is it used?
Modified metrically intensity scale, used in North America
What is the MSK scale and where is it used?
Medvedev- Sponheuer scale, used in Israel, Russia
What is the JMA 96 and where is it used?
The Japanese meteorological agency and used in japan
How may divisions does the jma sclae have?
7
What is the MMI scale based on?
Observations not equipment
What is intensity a product of?
Moment magnitude, PGA, focal depth and stance from the epicentre
What is M (moment magnitude) directly proportional to?
Ground factor
What is D (focal depth) indirectly proportional to?
The distance from the epicentre
What is the most hazardous region on earth?
The Kermadic islands
