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.


UN-SPIDER Regional Support Offices with hazard-specific expertise

Related content on the Knowledge Portal

  • NASA's Earth Observing System Data and Information System (EOSDIS) is a program for archiving and distributing Earth science data from multiple missions to users.
    Publishing institution:
  • Map Viewer that allows downloading and time series creation of meteosat products.
  • 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 Disaster Preparedness and Response in Latin America and the Caribbean. Guatemala:…

    read more
  • The Hazards Mapper home page is a base map of the world with darker shaded areas indicating higher population densities. Custom population estimates generated by the Hazards Mapper are provided by SEDAC’s Population Estimation Service (PES). Population and settlement data are based on SEDAC’s Global Rural-Urban Mapping Project (GRUMP) and Gridded Population of the World, version 3 (GPWv3) data collections. GPWv3 provides a resolution of roughly 4 km (2.5 miles) at the equator. This population resolution will increase significantly when the updated version, GPWv4, is released in 2016. “Our new population layer will be at a resolution of 1 km (0.6 miles) at the equator, which will give higher precision for smaller areas,” says de Sherbinin.

    Continuously updated data layers that can be overlaid on the base map are available from NASA’s EOSDIS, including data from SEDAC; NASA's Land, Atmosphere Near real-time Capability for EOS (LANCE); and Global Imagery Browse…, The default base map includes:

    Red dots indicating fires and other hotspots detected over the past 48 hours by NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) instrument;
    Colored circles indicating earthquakes over the past seven days from the USGS Earthquake Hazards Program;
    Icons indicating the location of individual dams, dam clusters, and nuclear power plants from SEDAC’s Global Reservoir and Dam and Population Exposure Estimates in Proximity to Nuclear Power Plants, Locations databases; and,
    Colored polygons indicating tornado and flood warnings issued by NOAA (U.S. locations only).
  • Hazards and Population Mapper (HazPop) is a free app that enables users to easily display recent natural hazard data in relationship to population, major infrastructure, and satellite imagery. Hazards data include the location of active fires over the past 48 hours; earthquake alerts over the past seven days; and yesterday′s air pollution data measured from space. The app shows the location of major dams and nuclear power plants and provides more detailed information and imagery for these facilities where available. By drawing a circle around a point or area of interest on the map, users can obtain an estimate of the total population and land area enclosed within., Developed by the NASA Socioeconomic Data and Applications Center (SEDAC) operated by the Center for International Earth Science Information Network (CIESIN) at Columbia University, HazPop combines data and map layers from various sources including NASA's Land, Atmosphere Near real-time Capability for EOS (LANCE) and Global Imagery Browse Services (GIBS), the U.S. Geological Survey (USGS), and others using a variety of open Web mapping services. The custom population estimates are provided by the SEDAC Population Estimation Service (PES) based on SEDAC′s Gridded Population of the World, version 4 (GPWv4) data for 2015.
  • The accuracy of the TanDEM-X 90m DEM relates to the TanDEM-X 12m (0.4 arcsec) DEM products from which it has been derived. For the 12m DEM: the Absolute horizontal and vertical accuracy is below 10m. The relative vertical accuracy expressed as linear errors at 90% confidence level (LE90) for slopes at or below 20% at 2m, and for slopes above 20% at 4m.

    The TanDEM-X 90m DEM product is delivered in a compressed ZIP (*zip) format. Each zip file contains a main folder, which contains basically the meta data of the product in XML (*.xml) format. In the main folder there are 3 subfolders:
    DEM: The DEM raster layer
    AUXFILES: The 7 information raster layer
    PREVIEW: All quicklook raster and KML files
    Publishing institution:
  • 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 Disaster Reduction Centre (ADRC) on behalf of the Indonesian National Institute of Aeronautics and Space (LAPAN). Both institutions are UN-SPIDER Regional Support Offices (RSO). Mapping products made available under the activation are available on the…

    read more

Term Parents

UN-SPIDER Regional Support Offices with hazard-specific expertise