What causes Earthquakes

An earthquake is the trembling of the earth’s surface caused by an abrupt energy release in the earth’s lithosphere that generates seismic waves. Earthquakes can vary in diameter from those so small that they are hardly felt to those powerful enough to drive things or people into the air and wreak havoc on entire cities. Seismic activity, or seismicity, is defined as the frequency, kind, and magnitude of earthquakes experienced during a given period. This paper will focus on the primary causes of earthquakes and their definition and recording way-outs. 

What is an earthquake definition?

When two slabs of the planet abruptly find a way out of one another, an earthquake occurs. The area on which they slide is the fault and the plane’s fault. The hypocenter is the region of earth’s crust where the earthquake originates, while the epicentre is the location exactly above the earth’s surface.

During an earthquake, foreshocks might occur. These are minor earthquakes that occur in the same area as the following major ones. Scientists won’t know if such a quake is a foreshock until the larger one hits. The mainshock is perhaps the most powerful and largest earthquake. Mainshocks are always the source of aftershocks. These are minor earthquakes that happen in a similar place as the mainshock. Though the aftershocks can last months, weeks, and even a few years, depending on the severity of the mainshock.

Earthquakes show themselves at the planet’s surface by shaking, displacing, or altering the ground. When a big earthquake’s epicentre is situated offshore, the seafloor may be moved sufficiently to generate a tsunami. Earthquakes can also cause landslides and, on rare occasions, volcanic activity. In its broadest sense, the term earthquake refers to any seismic activity that produces seismic waves, either natural or caused by humans.

What causes earthquakes?

Although the earth appears to be a reasonably solid entity from the surface, it is incredibly active just beneath the surface. The earth is divided into four main layers, “the solid crust, the hot and almost solid mantle, the outer liquid core, and the solid inner core”. 

The lithosphere is made of the solid crust and the uppermost, hard layer of the mantle. The lithosphere is not a single chunk surrounding the entire planet like an eggshell. Instead, it’s made up of substantial puzzle pieces called tectonic plates. Tectonic plates continually move about on the dense or gradually flowing mantle layer beneath them. This constant movement puts strain on the earth’s crust. When the tensions get too great, they cause fissures called faults. When tectonic plates flow, the faults move with them. An earthquake is defined as a sudden displacement of the earth’s crust along a fault line.

The epicentre is the place where an earthquake begins. Therefore, the most intense shaking during the earthquake is often experienced near the epicentre. However, earthquake vibrations can be felt and recognized hundreds, if not thousands, of miles apart from the epicentre.  

While the fault edges remain stuck together while the remainder of the block is flowing, the energy that might ordinarily force the blocks to move past each other is stored. Whenever the force of the sliding blocks eventually exceeds the resistance of the fault’s jagged edges, and it unsticks, all of the stored energy is released. Like ripples on a pond, energy radiates from the fracture in all directions. Seismic waves move through the earth, and when they reach the earth’s surface, they disturb the ground and everything on it.

How to record earthquakes?

The force from an earthquake flows through the earth in vibrations known as seismic waves. Seismometers are tools that scientists use to measure seismic waves. Seismometers detect seismic waves beneath the device and record them as zig-zags. Scientists can use seismometer data to identify an earthquake’s time, position, and severity. This report also contains details about the rocks through which the seismic waves passed.

The strength of an earthquake is determined by the size of a fault and the quantity of slip on the fault, which scientists cannot quantify with a measuring tape because faults are many kilometres beneath the earth’s surface. So, how do they calculate the magnitude of an earthquake? They use seismogram recordings collected on seismographs near the earth’s surface to determine the earthquake’s magnitude. A short wavy line that doesn’t jiggle indicates a minor earthquake, while a long wiggling line that wiggles a lot indicates a significant earthquake. The length of the wiggling line is proportional to the size of the fault, as well as the size of the wiggle is proportional to the amount of slide.

Conclusion

The magnitude of an earthquake refers to its size. Each earthquake has a single magnitude. Scientists also discuss the severity of an earthquake’s shaking, which changes based on where one is during the earthquake. Normal, reverse and strike-slip faults are the three main faults that might trigger an interplate earthquake. Normal and reverse faulting are instances of dip-slip, in which the movement along the fault is in the line of the dip, and movement on them has a vertical component.