Earthquakes

                           Earthquakes

Earthquake: Earthquake is a sudden shaking of ground caused by the passage of seismic

waves through Earth’s rocks.

Causes of earthquakes:

1. Tectonic Earthquakes

Earthquakes caused by tectonic plates are called tectonic quakes. They account for most

earthquakes worldwide and usually occur at the boundaries of tectonic plates. The Earth’s crust

consists of seven large lithospheric plates and numerous smaller plates. These plates move

towards each other (a convergent boundary), apart (a divergent boundary) or past each other (a

transform boundary).

Earthquakes occur most often along geologic faults, zones where rock masses move in relation

to one another. The major fault lines of the world are located at the fringes of the huge tectonic

plates that make up Earth’s crust. Earthquakes are caused by a sudden release of stress along

faults in the earth's crust. The continuous motion of tectonic plates causes a steady build-up of

pressure in the rock strata on both sides of a fault until the stress is sufficiently great that it is

released in a sudden, jerky movement. The resulting waves of seismic energy propagate through

2. Induced Earthquakes

Induced quakes are caused by human activity, like tunnel construction and fracking projects

3. Volcanic Earthquakes

Volcanic quakes are associated with active volcanism. They are generally not as powerful as

tectonic quakes and often occur relatively near the surface. Consequently, they are usually only

felt in the vicinity of the focus.

4. Collapse earthquakes

Collapse quakes can be triggered by such phenomena as cave-ins, mostly in karst areas or close

to mining facilities, as a result of collapsing.

Effects of earthquakes:

• Ground shaking

• Ground rupture

• Landslides

• Tsunamis

• Liquefaction

• Fires

Richter Magnitude scale

• The Richter magnitude scale is a scale of numbers used to tell the power

(or magnitude) of earthquakes

the ground and over its surface, causing the shaking we perceive as earthquakes.

Focus/hypocenter: The spot underground where the rock breaks is called the focus of the

earthquake.

Epicenter: The place right above the focus (on top of the ground) is called the epicenter of the