Earthquake fault types
An earthquake is a massive release in energy from the movement of the tectonic plates which make up the earth’s crust.
Areas of the earth’s surface where tectonic plates meet are known as faults, the tectonic plates slide past each other, but sometimes they become stuck and this causes energy to be stored, as the energy builds the plates will eventually become unstuck causing them to jolt quickly, releasing the stored up energy over a short period of time, this energy radiates outwards as what we call seismic waves. The more energy that was stored before the sudden release, the stronger the seismic waves.
Earthquakes are very difficult to predict but sometimes there are smaller shocks, called foreshocks which happen just before the mainshock, which can warn people to take precautions. Sometimes after the mainshock there can be powerful aftershocks which can happen any time after the earthquake, these are usually less powerful but can still be damaging.
The majority of the time earthquakes occur at fault lines and they’re less likely to happen elsewhere. This is why earthquakes are far more frequent in certain countries, because these countries are sitting on one or sometimes multiple fault lines.
How do we measure the strength of earthquakes?
The majority of earthquakes are too minor have an effect on people but sometimes they can be very destructive, the tremors being violent enough to destroy buildings or even entire cities. The magnitude of an earthquake is measured with a seismometer and the level is recorded on the Richter scale. The Richter scale is logarithmic, which means every point on the scale is ten times stronger than the last, so for example, an earthquake measured to be at 5.0 on the Richter scale is 10 times stronger than one measured to be at 4.0, which would make a 7.0 1000 times stronger than a 4.0 earthquake.
There are roughly 10,000 earthquakes a day around the world or around 3 million per year. The majority of these earthquakes measure at less than 3.0 on the Richter scale so they’re no felt by people. But occasionally earthquakes can be much stronger.
Earthquakes in History
While most earthquakes go unnoticed, sometimes they can be so strong they cause devastation.
The strongest earthquake ever to have been recorded was in Valdivia, Chile rated at 9.5 in magnitude. Nearly half the houses in in Valdivia were destroyed leaving around 20,000 people homeless and the resulting tsunami affected many other countries. It’s estimated that up to 6,000 people may have died as a result of the earthquake.
Destroyed houses in Chile
More recently was the 2004 earthquake in the Indian Ocean, this earthquake had a lower magnitude of roughly 9.0 but caused a tsunami so large it devastated many countries coastlines (particularly Indonesia, Sri Lanka, India and Thailand) and was one of the deadliest earthquakes in history.