Terminology related to Earthquakes

Earthquakes occur when two earth blocks slip past each other. The surface at which the slip occurs is named the fault plane. The hypocentre is generally situated below the earth’s surface, while above the earth, it will be denoted as the epicentre. 

More minor shocks might occur before the main earthquake. It is referred to as foreshocks. There are seven types of Seismic plates beneath the earth. Thus the knowledge of essential terms is beneficial.

Seismology 

Seismology is a scientific discipline for studying earthquakes. It is a part of geophysics that provides insights into the composition of the earth’s interior. The seismological investigations can be conducted on both local and regional levels. The investigations help identify subsurface faults, structural exploration, and related geophysical features like island arcs, ocean trenches, etc. 

In recent years, increased focus has been given to studying the movement of seismic plates and the prediction of earthquakes. Computer analysis has enabled the determination of seismic plates. The seismologists have successfully studied earthquakes implicated by varied human activities, impounding underneath water and others. Thus, the study of seismic plates in seismology relates to the search for ways to distinguish between explosions and earthquakes (which occur naturally). 

The terminology for earthquake under seismology is listed below 

• Epicentre: It forms the point in between the vertical free earth’s surface, and the earthquake originated place. In geography, it is denoted as latitude and longitude. In simpler words, it is the point above the earth’s surface where the earthquake has occurred. 
• Focus: It is also known as hypocentre and usually is the point of origination of seismic waves. The focal depth is generally calculated through the vertical distance between the hypocentre and epicentre. 
• Magnitudes: The earthquake’s energy is generally measured by its quantity, a size known as magnitude. It is not part of the observation of where the earthquake originated. The earthquake is classified under three categories of magnitude which are moderate, excellent and very high. The average magnitude ranges from 5.0 to 6.9, while the significant magnitudes will range from 7.0 to 7.9. The highest magnitude of 8.0 and above will destroy artificial structures and some natural structures (like the occurrence of landslides, the formation of plateaus and others). 
• Intensity: It is scales or ratings of earthquake effects from any place. The intensity of an earthquake is usually based on observations from the affected place. Descriptive scales such as the Modified Mercalli Scale are used to measure intensity. 
• Richter scale: The earthquake’s magnitude is measured by recording ground motion through an instrument. The tool or instrument is helpful for correctly recording the epicentral distance from the observation office. It has a linear relation with the logarithm of released energy from the earthquake and is usually expressed through the Richter scale. 

It is observed that there are seven seismic layers in alignment with the earth’s layers. The upper mantle and crust, part of the lithosphere, are rocky and brittle layers. It is further broken into seven types of seismic plates. The lithosphere also includes minor tectonic plates that fit together like pieces of puzzles.  

Theory of tectonic plates 

The sea floor and all the continents usually move around the surface of the earth. In the year 1950 and 1960s, scientists created seismographs for detecting atom bomb testing by enemy countries. This network of seismographs was also helpful to record earthquakes. The records have enabled scientists to measure and locate the epicentre. 

In simpler words, plate tectonic theories usually explain the formation of landforms due to the earth’s subterranean movements. This theory is ancient as it was developed in 1960 and had been helping scientists in explaining natural events like volcanic eruptions and earthquakes.  

The lithosphere is composed of large rocky plates located above the asthenosphere (molten rock layer). The convection of the asthenosphere and lithosphere results in the movement of plates. It is observed that each year, the plates move 15 centimetres to six inches. 

The interactive tectonic plates are accountable for several geological formations like Himalayan Mountain ranges in Asia, East African Rifts, Californian San Andreas Fault, etc.  

The aggressive movement of tectonic plates results in earthquakes and volcanoes. Hence, seismic records are beneficial to detect the epicentre of an earthquake. The earthquake’s epicentre will outline the plate-like mid-ocean ridges, trenches, significant faults and others. Many scientists call tectonic plates also refer to seismic plates. 

Conclusion 

Earthquakes occur when two earth blocks slip against each other. The surface at which the slip takes place is the fault plane. The sudden breakdown of rocks increases rapid motion. It releases energy due to which seismic waves are formed, which shakes the ground. 

Thus, scientists are focusing on seismic plates that predict an earthquake. Although, the common terminologies related to earthquakes might include magnitude, epicentre, Richter scale, intensity and focus. The article has also discussed explanations of seismology and tectonic plates.