Earthquake

Based on data from the Sentinel-1A satellite, this image shows how and where the land uplifted and sank from the 7.8-magnitude earthquake that struck Nepal on 25 April 2015. The image was generated by the German Aerospace Center (DLR) Earth Observation Center (EOC) using data acquired by Sentinel-1A before and after the earthquake event. Image: DLR/EOC.

Definition

Sudden movement of a block of the Earth’s crust along a geological fault and associated ground shaking (IRDR Glossary).

Earthquake can be defined as the shaking of earth caused by waves moving on and below the earth's surface and causing: surface faulting, tremors vibration, liquefaction, landslides, aftershocks and/or tsunamis (WHO).

 

Facts and figures

The size or magnitude of earthquakes is determined by measuring the amplitude of the seismic waves recorded on a seismograph and the distance of the seismograph from the earthquake. These are put into a formula which converts them to a magnitude, which is a measure of the energy released by the earthquake. For every unit increase in magnitude, there is roughly a thirty-fold increase in the energy released. Earthquake magnitude was traditionally measured on the Richter scale. It is often now calculated from seismic moment, which is proportional to the fault area multiplied by the average displacement on the fault (Australian Government).

There are four different types of earthquakes: tectonic, volcanic, collapse and explosion.

  • A tectonic earthquake is one that occurs when the earth's crust breaks due to geological forces on rocks and adjoining plates that cause physical and chemical changes.
  • A volcanic earthquake is any earthquake that results from tectonic forces which occur in conjunction with volcanic activity.
  • A collapse earthquake are small earthquakes in underground caverns and mines that are caused by seismic waves produced from the explosion of rock on the surface.
  • An explosion earthquake is an earthquake that is the result of the detonation of a nuclear and/or chemical device.
 

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Événement

UN-SPIDER and the National Secretariat for Science and Technology of Guatemala (SENACYT) join forces to conduct a seminar on the use of science, technology and innovation in disaster risk reduction and response efforts. The seminar entitled "Science and Technology: Applications for... read more

Actualités

Copernicus Emergency Management Service (© 2018 European Union), [EMSR317] Palu - Indonesia, Grading Map.

The International Charter “Space and Major Disasters” and the Copernicus Emergency Management Service Mapping have been activated on 29 September after a 7.5 magnitude earthquake in the central Indonesian Island of Sulawesi.

At least 844 people have been killed and 64,000 displaced according to reports.

The cities of Palu and Donggala are the worst affected areas by the earthquake and a tsunami with waves as high as six metres.

The International Charter was activated by the Asian... read more

Publishing date: 01/10/2018

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