Moments after an earthquake we all ask where it hit and how strong it was. To know, we turn to the media that obtains information from the seismological networks, through a press release, the respective websites and the social media.
However, location and magnitude vary, often causing confusion.
Which source has the correct information? The answer is: all of them!
In Costa Rica there are several key sources: The Red Sismológica Nacional (RSN: UCR-ICE), the Observatorio Vulcanológico y Sismológico de Costa Rica (OVSICORI – UNA) and the Laboratorio de Ingeniería Sísmica de la Universidad de Costa Rica (LIS-INII, UCR).
Information is also obtained by networks in the neighbouring countries: the Instituto Nicaragüense de Estudios Territoriales de Nicaragua (INETER), the Red sismológica de la Universidad de Panamá (IGC-UPA) and the Observatorio Sismológico del Occidente de Panamá (OSOP). And the big daddy of all networks, the United States Geological Survey (USGS).
After the occurrence of an earthquake it is common initial locations are revised to improve its quality. For example, data can be added more stations use different quality criteria for analysis of the signal, change the velocity model used and even location method.
The differences in reports is due to many factors, including as the number of seismic stations available, their spatial distribution in relation to the earthquake, the distance from the nearest station to the earthquake, seismologist ability to interpret the date and even the method used.
And then there is the updating of the information to improve the quality of the report. For example, data can be added from more stations using different criteria for analysis.
Some seismological networks use automatic report locations (by a computer program) as “preliminary”; then enhanced after analysis by seismologists.
Thus, the same earthquake, hitting the same place, can be reported differently, depending on the amount, type and quality of the data.