Earthquakes Flashcards
What are earthquakes?
Earthquakes are caused by the rapid release of energy stored.
What is the focus?
The focus is where the point of energy gets released.
What is the epicenter?
The epicenter is the point on the surface directly above the focus.
How come isostatic rebounds happen?
Isostatic rebounds happen because the Earth is relaxing. This relaxation is because the ground was weighted down during the Ice Age.
How do we mitigate against earthquakes?
The Earthquake Early Warning (EEW) system has a rapid detection of seconds to ten seconds before strong shaking starts.
What are the depths of the different types of waves?
Divergent/transform- shallow
Convergent- shallow to deep
What is a seismic wave?
Once an earthquake sets off this is the release in energy.
What are and what is the difference between magnitude and intensity?
A magnitude is the measurement of how much energy is released. The intensity is the result
Give me information about the Nepal Earthquake
Give me information about the Nepal Earthquake
April 25, 2015 Shallow- 8km, $10 billion dollars in damages
7.8 magnitude earthquake
Triggered landslides and avalanches
What is a Richter magnitude scale and a moment magnitude scale?
Richter magnitude- based on distance and amplitude or size of largest seismic wave produced, using a logarithmic scale.
Moment magnitude- measure of amount of energy released by earthquake taking into account movement, fault area and rock stiffness, making it more effective for larger earthquakes.
What is a fault?
A fault is the break between two blocks of rocks due to two rocks moving relative to each other.
Difference between elastic deformation and brittle deformation?
Elastic deformation is reversible and a brittle deformation is permanent and a rupture
What is the Modified Mercalli Intensity Scale?
This measures the effects instead of the intensity- qualitative way to describe/ compare earthquakes.
When measuring earthquakes what is the difference between magnitude and intensity?
Magnitude is quantitative; measures the amount of energy that is released at its source.
Intensity is qualitative; depends on the effects.
What is the process of a fault during an earthquake?
Original position, deformation, rupture and release of energy then rocks rebound to original undeformed shape.
What are the different faults?
Normal fault is the extension/tension
Reverse fault (locked fault) a fault gets locked and stress builds up
Strike-slip fault involves sheer stress
What is a primary hazard and an example?
Caused directly by fault movement (ground shaking, surface rupture)
What is a secondary hazard?
Caused as a consequence of fault movement (I.e. land elevation changes, landslides, tsunami,
Give me 5 examples of a secondary hazards?
Land elevation change
Landslides
Tsunami
Fires
Disease and poverty
What is a subduction zone?
Subduction zones are locked faults
What causes a subduction zone earthquake?
Locked by frictional resistance, buildup of strain, eventually releases along fault
What is an asperity?
Area on an active fault that is stuck or locked.
What happens with a locked fault
One plate is going under another and the one above gets locked, which causes a buildup of energy that produces an earthquake.
What is the after cause of a tsunami?
After a tsunami recedes the land scape elevation drops.
Where is the Cascadia Subduction zone and what 2 plates are involved?
West coast from some of Vancouver island to some of California. North American plate and Juan de Fuca Plate
What are clues about past earthquake activity?
In the soil and ghosts forests
