Area

Identifies the proximity of the earthquake epicenter to Catalonia. Three possible areas are defined:

• Local: earthquakes that occur within the area bounded by the coordinates 40.17ºN – 43.34ºN / 0.33ºW – 4.00ºE are considered local.
• Regional: earthquakes that are not local but occur within 3000 km of Catalonia are considered regional.
• Teleseism: earthquakes that occur more than 3000 km from Catalonia are considered teleseisms.

Date (UT)

Indicates the origin date and time of the earthquake in Universal Time (UT), also known as UTC (Coordinated Universal Time). Time in Catalonia is UTC+1 in winter and UTC+2 in summer.

Depth (km)

Indicates the depth, in kilometers, at which the earthquake hypocenter is located.

Imax

Maximum intensity is the highest value of macroseismic intensity observed in the area affected by an earthquake. It is based on the effects and damage caused to people, buildings, infrastructure, and the environment. Its main characteristics are:

• It is determined from direct observations, reports, and macroseismic surveys.
• It refers to the area where the earthquake was felt most strongly or caused the most damage.
• In Europe, it is generally expressed using the EMS-98 intensity scale, in Roman numerals.

This value is set as “Felt” when it is known that the earthquake was felt (Imax ≥ II), but there is insufficient data to determine the maximum intensity.

Latitude (º)

Indicates the latitude of the earthquake epicenter, expressed in decimal degrees, using the WGS84 reference system. The epicenter is the surface projection of the focus or hypocenter of the earthquake.

Longitude (º)

Indicates the longitude of the earthquake epicenter, expressed in decimal degrees, using the WGS84 reference system. The epicenter is the surface projection of the focus or hypocenter of the earthquake.

Magnitude

Indicates the magnitude of the earthquake, which is a quantitative measure of the energy released during the event, calculated from seismograms recorded at seismic stations. Its main characteristics are:

• An earthquake has a single magnitude, although it can be calculated using different methods.
• The scale is logarithmic. An increase of one unit in magnitude corresponds to about 10 times greater wave amplitude and roughly 32 times more released energy.
• It is independent of surface effects (how strongly it is felt). Effects are described using intensity.

The most common magnitude types are:

• Local magnitude (Ml): measures earthquake size based on wave amplitudes recorded at local distances (see Area). It is particularly suitable for small to moderate earthquakes.
• Body-wave magnitude (Mb): based on the amplitude of short-period P waves, making it useful for distant earthquakes, but it saturates for large events.
• Surface-wave magnitude (Ms): uses long-period surface waves. It is suitable for moderate to large earthquakes, although it also saturates at very high magnitudes.
• Duration magnitude (Md): estimates earthquake size from the duration of the seismic signal, making it especially useful for small earthquakes with low amplitudes.
• Moment magnitude (Mw): based on the seismic moment and tied to the physics of fault rupture, without saturation and applicable across all magnitude ranges.

Seismic release

Indicates whether a seismic alert release has been issued for the event. These releases are issued jointly with Civil Protection for local earthquakes with a magnitude equal to or greater than 2.2 or, regardless of magnitude, for any earthquake that has been felt in Catalonia.

Region

Name of the region where the earthquake epicenter is located. For local earthquakes, an epicentral regions map is used. For regional earthquakes and teleseisms, the region name is typically provided by the agency supplying the earthquake data.

Source

Indicates the acronym of the organization that provided the data for the epicentral location and the earthquake magnitude.

Type

Identifies the nature of the event that generated the seismic record. It distinguishes between earthquakes, explosions, and other phenomena of natural or anthropogenic origin, or even signals of unknown origin. Currently, the service publishes three types of events:

• Earthquake (ke): natural tectonic earthquake. Used when data show a clear, non-induced seismic source. Code: ‘ke’.
• Possible earthquake (se): possible natural tectonic earthquake. Used when data suggest a non-induced source, but are insufficient to confirm it. Code: ‘se’.
• Induced earthquake (ki): seismic event caused by human activity. Code: ‘ki’.