•Earth Structure Flashcards
What is an earthquake?
The intense shaking of the ground due to the release of elastic strain energy that has built up in response to crystal movement
What is a seismometer?
A device that records ground vibrations (Seismic waves)
What is a fault?
A fissure or crack in the Earth’s crust created by movement of rock during an earthquake
What is the foci?
The point within the Earth’s crust where an earthquake occurs
What is the Richter scale?
A measure of magnitude (explosive power) of a tremor
What is an epicentre?
A point on the surface immediately above the foci
What are seismic waves?
Waves of energy that ripple out from the foci
What are the layers of the Earth called?
What state are they?
What is their density?
Crust-solid-3.0
Upper mantle-solid-3.4
Asthenosphere-partially molten-3.3
Lower mantle-solid-3.5 to 3.5
Outer core-liquid-10.0
Inner core-solid-13.0
What are the characteristics of primary waves?
Compressional
Incompressibility
6kms-1
Travel through all materials
What are the characteristics of secondary waves?
Shear
Rigidity
3kms-1
Travel through solids and semi-solids
Changed to P waves when hits liquid
Where is earthquake pressure formed?
Generated by tectonic movement
Common along boundaries of collision
What order are waves found on a seismic reading?
P-waves
S-waves
Surface waves
What happens to the earthquake travel path in the crust?
Incidence > refraction = acceleration (speed up)
P wave= 6.5 kms-1
S wave= 3.1 kms-1
What happens to the earthquake travel path in the upper mantle?
Refraction > incidence = slow down
More incompressible than crust
More rigid than crust
P wave = 8.0 kms-1
S wave = 4.5 kms-1
What happens to the earthquake travel path in the asthenosphere?
Incidence > refraction = acceleration (speed up)
Less incompressible than upper m
Less rigid than upper m
P wave = 7.5kms-1
S wave = 4.0kms-1
