Blocks of land can move in several different ways relative to each other during an earthquake. This video shows the different types of motion.
Normal fault motion is where one overlying block of land moves or slides down relative to the lower block. This is a vertical movement. The M6.5 Edgecumbe 1987 earthquake is an example of normal faulting.
A reverse fault is where one block of land moves over top of the other one. A thrust fault is a certain type of reverse faulting where the angle of movement is less than 45 degrees. Reverse faulting occurs all over New Zealand. Many shallow earthquakes are reverse faulting, including the M6.2 Christchurch 2011 earthquake. Large, mega-thrust subduction zone earthquakes worldwide are always reverse faulting, such as the M9.1 Sumatra 2004 and M9.1 Tohoku 2011 earthquakes. They often cause a tsunami due to displacing the water vertically when the seafloor thrusts up.
Blind thrust fault is where a reverse fault earthquake does not rupture the Earth’s surface. A reverse fault is where one block of land moves over top of the other one. Blind faults are where any type of fault motion produces an earthquake that doesn’t rupture the Earth’s surface. It is rare that an earthquake ruptures the surface, because most earthquakes are not big enough and occur several kilometres or more below the surface.
Strike-slip faulting is where two blocks of land on either side of the fault move past each other horizontally. There is very little up or down movement. The Alpine Fault is the most well-known fault in New Zealand to move in a strike-slip motion. The Greendale Fault (M7.1 Darfield 2010 earthquake) moved in strike-slip motion and ruptured the Earth’s surface. You can often see metres of horizontal displacement in large enough strike-slip earthquakes.
Oblique fault: An earthquake that is a combination of strike-slip and reverse or normal faulting, with a combined horizontal and vertical component. The Wairarapa and Wellington Faults are examples of this type of oblique fault, with a horizontal and vertical component.
Source: GNS Science
