Fault
These are cracks or breaks in the surface of the earth.
These are the most obvious indications of earthquake activity.
Earthquake
Occurs due to rock movements at the faults.
Whether the cracks are deep or shallow, there are deformations in the surrounding rock features.
Stress - Force exerted in the rocks
Shearing Stress - happens when forces slide past each other in opposite directions.
most common stress found at Transform Plate Boundaries
Compression Stress - stress squeezes rocks together. Causes rocks to fold or fracture. It is also the most common stress at convergent plate boundaries.
Tension Stress - Pulls rocks apart. Causes rocks to lengthen or break apart. Tension is the major type of stress found at divergent plate boundaries.
Fault Plane - The plane along which the rock or crustal material has fractured.
Hanging Wall Block - The rock material which lies above the fault plane.
Footwall Block - The rock material below the fault plane .

Lesson 2: Types Of Faults
Dip-slip Fault - Has a dip angle, which means the crack or strike is slanted.
Normal Fault - Caused by tension forces where plates diverge. The fault is at an angle where the Footwall block is hanging on the hanging wall block. When movement occurs on a normal fault the hanging wall slips downward.
Reverse Fault - Caused by compression forces along convergent plate boundaries. As the same structure as a normal fault, but blocks move in the opposite direction. Where the hanging wall is on top of the footwall.
Strike-slip Fault - Created by shearing along transform boundaries.Rocks on either side of fault slip past each other sideways with a little up-or-down motion.
Strike Slip right - Wherein the right lateral strike slip fault.
Strike Slip left - Wherein the left lateral strike slip fault.
Oblique-Slip Fault - Movements are a combination of the movements of a strike-slip and dip-slip fault. The fault slips into simultaneous directions, a combination of vertical and horizontal..
Active, Inactive and Reactive Faults
Active Faults
Exhibit much movement.
Crustal movements and displacements are expected and detected.
Inactive Faults
Do not have movement’s characteristics of earthquakes.
If the rocks indicate that the fault has not been active for millions of years, a fault is considered inactive.
Active faults may induce renewed activity in adjacent faults. An inactive fault may be reactivated by the forces and stresses in the crust.

Lesson 3: General Structure Of The Earth
Layers Of The Earth
Crust - It is a solid layer of rock on the surface of the planet. The thickness varies 3 to 30 miles.
Mantle - It is a semi-liquid layer of magma, or molten rock, that moves due to