About Earthquakes

Types of Earthquakes


  • A tectonic earthquake is one that occurs when the earth's crust breaks due to geological forces on rocks and adjoining plates that cause physical and chemical changes.

  • A volcanic earthquake is any earthquake that results from tectonic forces which occur in conjunction with volcanic activity.

  • A collapse earthquake are small earthquakes in underground caverns and mines that are caused by seismic waves produced from the explosion of rock on the surface.

  • An explosion earthquake is an earthquake that is the result of the detonation of a nuclear and/or chemical device.


types of faults
  • Normal faults form when the hanging wall drops down. The forces that create normal faults are pulling the sides apart, or extensional.

  • Reverse faults form when the hanging wall moves up. The forces creating reverse faults are compressional, pushing the sides together.

  •  Transcurrent or Strike-slip faults have walls that move sideways, not up or down.

What are the types of earthquakes?


Earthquakes can come in three main forms, depending on the plate movements that occur beneath the earth's surface. They could occur on a Convergent Boundary, Divergent Boundary or a Transform Fault.

Type of Earthquakes

Convergent boundary:  Here, one plate is forced over another plate during movement creating a thrust fault.

Divergent boundary:  Here, plates are forced apart each other, usually forming a Rift Zone. This kind is common in ocean floors where new floors are created. An example is the Mid Atlantic Ridge.

Transform fault: Unlike divergent and convergent, the plates here slip by each other. This is also called Strike-Slip.

New research shows that a big earthquake can not only cause other quakes, but large ones, and on the opposite side of the Earth. ... "Earthquakes are part of a cycle of tectonic stress buildup and release. As fault zones near the end of this seismic cycle, tipping points may be reached and triggering can occur."

Deep Earthquake Zones
Deep Earthquake Zones

After a period of time, the built-up energy and movement causes huge tension in the plates, and there is massive pressure on the fault lines. This intense pressure resulting from energy build up causes the fault lines give way, and plates move over, against or apart from each other.

Subduction Zones Worldwide

Earthquake  Waves

There are 2 types of earthquakes waves and the difference lies in the way the seismic waves are transmitted. To understand this better, let us see what a seismic wave is.

These are waves of energy that travel through the earth's layers, and other elastic layers, often as a result of earthquakes. A wave, by general definition is the transfer of energy from one place to another without transferring solid, liquid or gas matter. Examples include light and sound waves.

During an earthquake, the waves released may be “P” or “S” waves depending on the speed and ways in which they travel.

P-Waves (Primary Waves)
p-wave of seismic wave

P-waves are longitudinal in nature. The vibrations are along the same direction as the direction of travel. It is also known as compressional waves. P-waves travel faster than S-waves.


S-Waves (Secondary waves)
s-wave
Here the waves travel at right angles to the direction of travel. They are also known as transverse waves and example include water waves.