Earthquake

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.

Further information

USGS Earthquakes

PreventionWeb Earthquakes

UN-SPIDER Regional Support Offices with hazard-specific expertise

Title: Asian Disaster Reduction Center (ADRC)

Title: Germany Regional Support Office

Title: Greece Regional Support Office

Title: Indonesia Regional Support Office

Title: International Centre for Integrated Mountain Development (ICIMOD)

Title: Pakistan Regional Support Office

Title: United States of America Regional Support Office

Related content on the Knowledge Portal

Earthquake in Honduras

On 28 May 2009, at 2:24 a.m. an earthquake measuring 7.1 on the Richter scale, struck the Northern part of Honduras at a depth of 10km. The epicenter was located between the island of Roatan and Guanaja, but it was felt throughout the country.

Source : Glide number

Ressources from OCHA / Reliefweb, click here
Earthquake in Salvador

A swarm of earthquake struck the western region during the first week of May. 42 houses damaged and more than 200 people affected.

Source : Glide number
Earthquake in Afghanistan

Two earthquakes killed at least 22 people and destroyed several hundred homes when they struck two hours apart in eastern Afghanistan (17/04/2009).

Source : Glide number

Ressources from OCHA/Reliefweb, click here
Earthquake in Italy

A number of people were reported to have been injured and others trapped under rubble in the city of l'Aquila and outlying areas from the quake that measured 6.3 on the Richter scale.

Source : Glide number

Ressources from OCHA /Reliefweb, click here
Earthquake in Pakistan

An earthquake of magnitude 5.8 struck the Kashmir valley in Pakistan on 20 Feb 2009 local time. There were no reports of deaths, but damage was said to be widespread, particularly in the Neelum Valley area north of Muzaffarabad.

Source : Glide number
Earthquake in Indonesia

On 2/11/2009 5:34:50 PM UTC an earthquake of magnitude 7.2 and depth 20km has struck an moderately populated area in the Sulawesi Utara Province (population: 2.6 million) in Indonesia. GDACS estimates the likelihood for need of international humanitarian intervention to be medium (Orange alert). It is likely that a tsunami was generated. The maximum tsunami wave height near the coast of Indonesia, Sulawesi Tengah will be 1.6m. Please refer to the GDACS tsunami report for more details. This earthquake can have a medium humanitarian impact since the affected region is moderately populated and has medium vulnerability to natural disasters.

Source : Glide number
Earthquake in China, P. Rep

Thousands of people have been made homeless by an earthquake on Sunday 25 January in remote Qapqal, in China's far western region of Xinjiang near the Kazakh border.

Source : Glide number
Earthquake in Costa Rica

Death toll 14: AFP

Source : Glide number

A 6.1-magnitude earthquake shook north-central Costa Rica on 8 January and many rural towns have been under serious landslide threat. At least 220 people were injured during the earthquake and 34 people died. Electrical infrastructure and roads were also seriously damaged.

Source : International Charter for "Space and Major Disaster"

Ressources from OCHA/Reliefweb, click here

Map Ressources :

Landslides

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Earthquake in Indonesia

A magnitude 7.6 earthquake struck off the northern coast of the island of Papua in Indonesia. Hundreds of people had gathered at a football stadium seeking medical aid for minor injuries.

Source : Glide number

Ressources from OCHA/Reliefweb, click here
Earthquake in New Zealand

On 7/15/2009 9:22:33 AM, an earthquake of magnitude 7.8 and depth 33km occurred in New Zealand generating a small tsunami with estimated maximum wave height of 0.3 m.
Source : Glide number
Ressources from Earthquake Hazards Program, click here.