Locations at risk from tectonic hazards

DIVERGENT (CONSTRUCTIVE):

• Displayed at mid -cean ridges, numerous low magnitude earthquakes,many are under the sea

CONVERGENT:

• Plates move together, activley deform collision locations with plate material melting in the mantle, frequent volcanoes and earthquakes

CONSERVATIVE (TRANSFORM):

• Plates move past each other, lithosphere is neither created nor subducted, no volcanic activity, numerous shallow focused earthquakes

The zone of magma 'locking in' or 'striking' the Earth's magnetic polarity when it cools. Scientists use this tool to determine historic periods of large-scale tectonic activity through the reconstruction of relative plate motions

• The Benioff Zone is an area of seismicity corresponding with the slab being thrust downwards in a subduction zone. 
• Subduction zones are broad areas where two plates are moving together, often with the thinner, more dense oceanic plate descending beneath a contintental plate. The contact between the plates is sometimes called a thrust or mega-thrust fault. Where the plates are locked together, frictional stress builds. The release of stress causes a mega-thrust earthquake. 
• Locked fault: A fault that is not slipping because the frictional resistance on the fault is greater than the shear stress across the fault, that is, it is stuck.

PRIMARY OR P WAVES:

Vibrations caused by compression, spread quickly, travel through liquids

SECONDARY OR S WAVES:

Move more slowly, vibrate at right angles to the direction of travel, cannot travel through liquids

LOVE WAVES OR L WAVES:

Surface waves with the vibration occuring in the horizontal plain, have a high amplitude

A tsunami is a series of waves generated in an ocean or other body of water by a disturbance such as an earthquake, landslide, volcanic eruption, or meteorite impact. The picture at the left shows how an earthquake can generate a tsunami in the overlying water.

Undersea earthquakes, which typically occur at boundaries between Earth's tectonic plates, cause the water above to be moved up or down. Tsunami waves are formed as the displaced water, which acts under the influence of gravity, attempts to find a stable position again.

Undersea landslides, which can be caused by large earthquakes, can also cause tsunami waves to form as water attempts to find a stable position.

Undersea volcano eruptions can create enough force to uplift the water column and generate a tsunami.

Asteroid impacts disturb the water from above, as momentum from falling debris is transferred to the water into which the debris falls.