unit 7: dynamic earth topic: earthquakes - t-birds earth...
TRANSCRIPT
Unit 7: Dynamic Earth Topic: Earthquakes
Time for a new note packet!
Sub-project 1: Earthquake Risk
International experience, including tragic lessons from recent large earthquakes, shows that the growth of earthquake prone communities, following the global processes of development and urbanization, commonly gives rise to seismic risk unless proper countermeasures are taken to prepare for future earthquakes and manage the risk. This is true as well for the countries of low and moderate seismicity taking into account that the risk value depends not only on the hazard level, but also on the aggregate elements at risk and their vulnerability to probable seismic influence. Thus, the proper approach to the problem of risk assessment and risk management should include consideration of all the contributing factors:
Hazard:
Living in seismic prone areas means that seismic risk is unavoidable. It is impossible to manage the risk through prevention of future earthquakes. But improvement of seismic hazard assessment and providing reliable seismological and engineering-seismological information for planning and design purposes is an important factor contributing to efficiency of risk management programs.
Exposure (elements at risk):
When earthquakes occur in uninhabited areas they are not considered as disasters. Sometimes civilization and urbanization make human beings more vulnerable to the natural phenomena. It happens, in particular, when there is high concentration of population and complicated infrastructure in earthquake prone zones. So, the processes of land use and urban planning as well as development of new technologies should take into account the existing seismic threat.
Vulnerability:
The bitter engineering truth is that earthquakes do not kill people, vulnerable buildings do. Though future earthquakes cannot be avoided, the community can improve seismic performance of buildings and lifelines, reconstruct or retrofit old structures and build new earthquake-resistant constructions, in particular, for residential and critical buildings.
Awareness:
Lack of awareness (as a psychological component of vulnerability) contributes to seismic risk considerably. It concerns people from every sector of the community, all members of which are to realize how to prepare for possible disasters, how to behave if an earthquake strikes and what to do after.
Earthquake
Shaking caused by rapid movement of
crustal rock
Plastic Mantle
Fault
Earthquake Fault
Shaking caused by rapid movement of
rock
Crack within the Earth where the rock slips, or
moves
One Famous Fault in the USA The San Andreas Fault in California
Focus
Earthquake Fault Focus
Shaking caused by rapid movement of
rock
Crack within the Earth where the rock slips, or
moves
In the Earth where the earthquake occurs
Epicenter
Earthquake Fault Focus
Epicenter
Shaking caused by rapid movement of
rock
Crack within the Earth where the rock slips, or
moves
In the Earth where the earthquake occurs
On the surface directly above the focus
Topic: Seismic (Earthquake) Waves
Energy waves from an earthquake
1) P-waves (Primary)
2) S-waves (Secondary)
3) L-waves (Surface Waves)
Seismic Waves
1. Primary (P) Waves
2. Secondary (S) Waves
3. Surface (L) Waves
Compression waves First Fastest Through solid, liquid, gas
Shear waves Second Slower Through solids only
Surface waves Slowest Cause most damage
Seismograph
Used to detect the strength of an earthquake and
location
Japan Earthquake, 3/11/2011 Skidmore College, NY Seismograph
YOUR BEST FRIEND
Page 11
Richter Scale
(Magnitude)
Measures the
magnitude (the
amount of
energy released)
Mercalli Scale –
Measures intensity,
the earthquake’s
effect on people
and buildings.
Moment Magnitude Scale
Explained
http://www.iris.edu/hq/programs/education_
and_outreach/animations/26
Crust
Mantle
Outer Core Inner
Core
Simple Model of Earth’s
Interior
Waves refract (bend) in different densities
Earthquake waves tell us what the interior of the Earth is like!
We believe the outer core is a liquid because S-waves stop at this layer.
What type of wave?
What type of wave?
What is this point called?
Earth’s surface
Focus
What is this point called?
Earth’s surface
Focus
Epicenter
Final Question
Which seismic wave type travels the slowest?
Final Question
What is the name given to a location where an earthquake originates?
