What is an earthquake?

An earthquake is a sudden release of energy in the Earth's crust that creates seismic waves.

Earthquake in Turkey

Table of Contents

Context: Three earthquakes measuring — 7.8, 7.6, and 6.0 — magnitude has devastated Turkey and Syria, while impacting regions as far away as Cyprus, Lebanon, Israel, and Egypt.

Turkey’s Vulnerability to Earthquakes

Turkey is frequently shaken by earthquakes. In 2020 itself, it recorded almost 33,000 earthquakes in the region.
According to one estimate, almost 95% of the country’s land mass is prone to earthquakes.
Tectonic location: Turkey’s proneness to earthquakes comes from its tectonic location.
- Turkey is located on the Anatolian tectonic plate, which is wedged between the Eurasian and African plates.
- Arabia is moving northwards into Europe, causing the Anatolian plate (which Turkey sits on) to be pushed out westwards.
- The movement of the tectonic plates builds up pressure on fault zones at their boundaries. It is the sudden release of this pressure that causes earthquakes and ground shaking.
Major fault lines:
- North Anatolian fault (NAF) line: It is the meeting point of the Eurasian and Anatolian tectonic plates — is known to be “particularly devastating”.
- East Anatolian fault line: It is the tectonic boundary between the Anatolian Plate and the northward-moving Arabian Plate.

About Earthquakes

An earthquake is a sudden release of energy in the Earth’s crust that creates seismic waves.
Key terms related to earthquakes:
- Focus: The focus, also known as the hypocentre, is the point within the Earth where an earthquake originates.
- Epicenter: The point on the Earth’s surface directly above the focus or source of an earthquake.
- Aftershocks: Smaller earthquakes that occur after a larger earthquake, as the Earth adjusts to the sudden movement.
- Seismic waves: The waves of energy that travel through the Earth’s crust and cause ground shaking during an earthquake.
Causes of earthquakes:
- Plate tectonics: The movement of the Earth’s tectonic plates can cause earthquakes when the plates interact along plate boundaries.
- Volcanic activity: Earthquakes can occur when magma moves beneath a volcano, causing the ground to shake.
- Human activity: Human activities, such as the injection of fluid into the ground for waste disposal, or the extraction of oil and gas from underground reservoirs, can induce earthquakes.
- Reservoir-induced earthquakes: The filling or emptying of large reservoirs, such as lakes or dams, can cause earthquakes as the weight of the water changes and affects the Earth’s crust.
- Glacial rebound: The movement of glaciers can cause earthquakes as they advance or retreat and cause changes in the Earth’s crust.
Measurement of earthquakes: The magnitude and intensity of an earthquake are two ways to measure its size and impact.
- Magnitude: The magnitude of an earthquake is a measure of its energy release, and is determined from measurements of the seismic waves generated by the earthquake.
  - The most commonly used scale for measuring earthquake magnitude is the Richter scale, which was developed in the 1930s.
  - The Richter scale ranges from 0 to 9, with each increase in magnitude representing a tenfold increase in energy release.
- Intensity: The intensity of an earthquake is a measure of its impact at a specific location, and is determined by the effects of the seismic waves on the ground, buildings, and people.
  - The most commonly used scale for measuring earthquake intensity is the Modified Mercalli Intensity (MMI) scale, which ranges from I to XII.
  - The MMI scale takes into account factors such as the type of building construction, the height of the building, and the distance from the earthquake’s epicenter.
Seismic waves: Seismic waves are waves of energy that travel through the Earth’s crust and cause the ground to shake during an earthquake.