Earthquakes
A fault is a break in the Earth’s crust where the rocks on either side have slid past each other and are independent of each other. When they rub, it causes stress and when the tension and to release this energy, the two plates slip/move and create earthquakes.
Earthquakes are measured with seismographs which records details such as force and duration.
Parts of an Earthquake
Focus
This is the location where the earthquake begins. It is where the plates slip and is always on a fault line at the plate edges. A focus can be shallow and deep but deeper quakes are stronger than shallow ones.
Epicentre
This is the point on the earth’s surface that is directly above the focus, the point where an earthquake and underground explosion originates.
Parts of a fault
Fault plane, fault trace, hanging wall and footwall
Fault plane : when the action is, the area where the fault occurred,
Fault trace: line created by a fault plane
Hanging wall : the rock that is on top of the fault line
Footwall : the rock that is underneath the fault line
When the fault plane is vertical, there is no hanging wall or footwall.
The cliff-like feature the fault creates is called a fault scarp
Type of faults
Normal, reverse and strike-slip
Normal faults form when the hanging wall drops down. They are created by pulling the sides apart (is extensional) [Convergent boundary]
Reverse faults form when the hanging wall moves up. They are created by compression, which is pushing the sides together. [Divergent boundary]
Strike-slip faults have walls that move sideways, not up or down. In these faults the fault plane is usually vertical, so there is no hanging wall or footwall. The forces creating these faults are horizontal, carrying the sides past each other. [Transform boundary]
Earthquakes are measured with seismographs which records details such as force and duration.
Parts of an Earthquake
Focus
This is the location where the earthquake begins. It is where the plates slip and is always on a fault line at the plate edges. A focus can be shallow and deep but deeper quakes are stronger than shallow ones.
Epicentre
This is the point on the earth’s surface that is directly above the focus, the point where an earthquake and underground explosion originates.
Parts of a fault
Fault plane, fault trace, hanging wall and footwall
Fault plane : when the action is, the area where the fault occurred,
Fault trace: line created by a fault plane
Hanging wall : the rock that is on top of the fault line
Footwall : the rock that is underneath the fault line
When the fault plane is vertical, there is no hanging wall or footwall.
The cliff-like feature the fault creates is called a fault scarp
Type of faults
Normal, reverse and strike-slip
Normal faults form when the hanging wall drops down. They are created by pulling the sides apart (is extensional) [Convergent boundary]
Reverse faults form when the hanging wall moves up. They are created by compression, which is pushing the sides together. [Divergent boundary]
Strike-slip faults have walls that move sideways, not up or down. In these faults the fault plane is usually vertical, so there is no hanging wall or footwall. The forces creating these faults are horizontal, carrying the sides past each other. [Transform boundary]