When there’s an earthquake, be it under our feet on the other side of the world, having reliable and accurate information quickly is essential for several reasons, first of all the safety of the population.
We are used to obtaining this information from our reference news sources or, increasingly, from social media. But where does this information come from? Who provides the magnitude, depth and location of the epicenter when there’s an earthquake?
The bodies responsible for seismic monitoring, that is, those involved in detecting events and in their estimation, are different and generally each nation has its own. Three of the most important for earthquakes in Italy and in the world are the National Institute of Geophysics and Volcanology(INGV) , the United States Geological Survey (USGS) and the Euro-Mediterranean Seismological Center (CSEM – EMSC).
The first reference is the Istituto Nazionale di Geofisica e Vulcanologia, the Italian body in charge for the seismic monitoring in Italy. The data it provides is available across multiple channels, but primarily through the website terremoti.ingv.it. Here earthquakes are classified according to date (from the most to the least recent), magnitude (from the strongest to the weakest) and the zone.
The data comes directly from the Seismic Room of the INGV where the operators assigned to seismic monitoring working 24 hours a day, 7 days a week validate the outputs within 30 minutes from the earthquake.
The INGV page dedicated to the real time monitoring of earthquakes
The same data is available on the INGVterremoti app, which also allows you to sort earthquakes based on the distance from where you are (therefore particularly useful for understanding if the vibration we felt was a real shock or just our imagination).
If app and website are not sufficient, lINGV has also a Facebook page and a Twitter account: here not only theautomatic estimates are published within minutes of an earthquake, but within half an hour the validated data (i.e. verified) are provided.
Bonus: the app contains a “Story Maps” section that collects insights into the most relevant events of the recent past.
United States Geological Survey
Across the pond the United States Geological Survey, USGS, is the reference. Like INGV, also USGS is involved in the seismic monitoring at the national and global scale and makes its data available on its website and social media, mainly Twitter. On this microblogging platform, there are seven accounts dedicated to earthquakes: from the bot account that provides real time date, to theone dedicated to outreach, up to one dedicated to the seismic instrumentation and the one of the ShakeAlert programme, an early warning system able to alert the population a few seconds before an earthquake (they may seem few, but especially when it comes to earthquakes with high magnitude they can be crucial).
The world map with the latest earthquakes indicated on the USGS website
Bonus: the site has a world map on which the latest earthquakes are represented. You can decide what to see as a map, for example only the ocean floors, continents or roads. In addition, the edges of the plates are indicated and, only for the US (unfortunately), the main faults are shown… and here I recommend you to take a look at the San Francisco area!
European Mediterranean Seismological Centre
The third reference body is the European Mediterranean Seismological Centre (EMSC), a scientific NGO founded in 1975 which combines the seismological observations at the Euro-Mediterranean level of 85 institutes from 56 different countries. Although also in this case the data of magnitude, time, date, location of the epicenter and depth is available on the dedicated website, there are actually three bonuses.
The first is the LastQuake app which, in addition to showing the earthquakes closest to where we are, allows you also to search only for the most significant events. But above all, it signals very clearly a possible tsunami alert (even if it is later withdrawn) and allows you to give your contribution if you have felt an earthquake, by writing a comment or uploading an image.
@LastQuake Twitter account of the European Mediterranean Seismological Centre
The second is the excellent @LastQuake Twitter account, which not only tweets about earthquakes in real time, but also provides interesting insights and answers during the events.
Last but not least, the last one is the Telegram channel LastQuake2 (and, maybe, this is my favourite one): in addition to earthquakes in real time, it also provides other contenta, such as seismic maps created by the data provided by the citizen science surveys. But beware, here you will receive many more notifications than you imagine …
Why three references?
Indeed, one references is (or rather, should) be more than enough to keep up with the latest earthquakes. And, in most cases, it is.
The three bodies described above provide the data they calculate on each earthquake, and often (indeed, almost always), the values they obtain are slightly different from each other. In other words, for the same earthquake, the magnitude and depth of the epicenter are similar, but not the same.
But while this may seem a contradiction, it really isn’t. When it comes to locating an earthquake, what technicians and seismologists do is estimate these values through seismic wave propagation models, which are based on the current knowledge available. Furthermore, when it comes to magnitude, there is no single definition, but there are several, more or less suitable for various situations (for example, if the earthquake has a magnitude greater than 6.0 or if it occurred in a volcanic area).
Since we are talking about “estimates”, it is normal that there are differences, given that the tools used (the models), the information (the seismograms collected by seismometers) and the type of estimated magnitude are different. A bit like if we all had to estimate the height of a building, each using its own set of information (how many floors the building has, how high each floor is, etc.), perhaps with a different definition of height (for me is from the ground floor to the top floor, for another person it also includes the roof). Eventually we would get similar, but not the same, values.
Therefore, there are no exact magnitude and depth values for each event, but estimates that are close to each other, which provide an idea of the characteristics of the earthquake. Obviously, for those involved in research, these variations are fundamental and extremely interesting, but, if we want to be honest, in everyday life they are almost irrelevant. So yes, looking for information on just one of these entities is more than enough, but comparing it with that provided by the others is at least fascinating.