EARTHQUAKES

 

These days we hear much about earthquakes in relation to the magnitude 7.8 earthquake that hit Turkey and Syria on the morning of Monday 6th February. This earthquake was destructive; razing cities to the ground and killing more than 40 thousand people. In addition to this, it has also inflicted immeasurable damage on the cultural lands of Syria and Turkey by destroying the oldest city in the world: Aleppo.  

                

 

But what is an earthquake? An earthquake is an intense shaking of Earth’s surface. The shaking is caused by movements in Earth’s outermost layer. 

There are three different types of earthquakes: 

-Induced Earthquake; they are caused by human activity, like tunnel construction, filling reservoirs and implementing geothermal or fracking projects.

-Volcanic Earthquakes; they 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 hypocentre.

-Collapse Earthquakes; they can be triggered by such phenomena as cave-ins, mostly in karst areas or close to mining facilities, as a result of subsidence.

Why Do Earthquakes Happen?

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

The location where an earthquake begins is called the epicenter. An earthquake’s most intense shaking is often felt near the epicenter. However, the vibrations from an earthquake can still be felt and detected hundreds, or even thousands of miles away from the epicenter.

 

How Do We Measure Earthquakes?

The energy from an earthquake travels through Earth in vibrations called seismic waves. Scientists can measure these seismic waves on instruments called seismometer. A seismometer detects seismic waves below the instrument and records them as a series of zig-zags.    

Scientists can determine the time, location and intensity of an earthquake from the information recorded by a seismometer. This record also provides information about the rocks the seismic waves travelled through.

 

Do Earthquakes Only Happen on Earth?

Earthquake is a name for seismic activity on Earth, but Earth isn’t the only place with seismic activity. Scientists have measured quakes on Earth's Moon, and see evidence for seismic activity on Mars, Venus and several moons of Jupiter, too. NASA’s mission took a seismometer to Mars to study seismic activity there, known as marsquakes. On Earth, we know that different materials vibrate in different ways. By studying the vibrations from marsquakes, scientists hope to figure out what materials are found on the inside of Mars.

 

                                                                                                      Alessia, 5scB