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How it works & Disclaimer

Towards our goal of providing and disseminating earthquake information as quickly as possible, the EMSC has developed a system to rapidly detect felt events through the real-time analysis of our web site traffic. In the event of a felt earthquake, eyewitnesses rush to our website to find information about the shaking they just felt. Therefore, the first manifestation of a felt earthquake in an area where the EMSC is well-known is a flash-crowd (i.e. a sudden surge in the number of visitors to the website). It is typically detected within 30 to 90 seconds of the earthquake's occurrence. Thanks to a partnership with DigitalElement, the geographical region(s) of origin of the eyewitnesses are automatically determined through their IP addresses.

When it triggers, this novel system allows us to detect the occurrence of a felt earthquake much more quickly than traditional seismological methods. It is, however, still an area of active research and a system under development, and, although so far it proved remarkly reliable, it is not yet 100% accurate. Smaller or remote events, and events in areas where the EMSC is not yet well-known, may go undetected.

How it works

When eyewitnesses feel the ground shaking they turn instantaneously to the Internet to find out the cause of the ground motion. Many reach the EMSC website, the second most popular earthquake information website generating massive and instantaneous increases in traffic. Once the surge has been detected, EMSC identifies the geographical origin of the eyewitnesses to map where the earthquake was felt. To identify the origin of this traffic, the EMSC uses geolocation technology, which uncovers the geographical location of eyewitness activity based solely on users’ Internet Protocol (IP) addresses. This allows the EMSC to identify the origin of quake activity before the first reports from seismological monitoring networks are issued.

The detection is on average, within 90 seconds following the earthquake occurrence. When the cause of the earthquake is reported several minutes later by the seismological networks, a second message is published that identifies the location, origination time, and magnitude of the earthquake. Messages are also published on twitter (@lastquake)

In addition to the service’s unique ability to rapidly identify felt quake activity, another key benefit is the ability to identify activity that causes public concern. Leveraged alongside classical tools for earthquake monitoring, the EMSC’s real-time service shortens the length of time it has traditionally taken to disseminate information to the public. An example of actual tweets is provided below.

How does the detection of felt earthquakes actually work?

Felt earthquakes are detected through traffic surges generated on the EMSC website*. Earthquakes which are felt in countries where the EMSC website is well known by the public (mainly in Europe) cause immediate surges of traffic on our site. These surges reflect the massive convergence of eyewitnesses on the site.

How do you identify the region where the earthquake was felt?

Through the IP (Internet Protocol) address of the eyewitnesses. The IP location service is provided by Digital Element in the framework of a partnership with the EMSC. Locations are given at the city level and cannot be used to identify individuals.

What is the benefit of this service?

The main benefit of this service is to focus on the effects of the earthquake rather than its geophysical characteristics (magnitude, location). This is fundamental information needed by the public, where measurement of the effects of the earthquake are more significant than the magnitude. Rapid identification of felt earthquakes improves the way answers can be provided to both citizens and authorities.

What is the benefit of publishing the information on Twitter?

The EMSC’s real-time service shortens the length of time it has traditionally taken to disseminate information to the public. Sharing this information on Twitter allows anybody to evaluate the service performances on their own. Also, because questions and comments are welcome, it creates a community of information sharing.

How many felt earthquakes are detected?

During the last 24 months, an average of two felt earthquakes have been detected a month. This is only an average and in case of aftershocks, several felt earthquakes can be detected in a single day.

How reliable is the service?

No automatic system can pretend to be 100-percent reliable. During the last two years, we have been working to strengthen the reliability of the detection. During this period, there has been only one false trigger (i.e. a detection which had not been caused by an earthquake). Even if reliability were more important than rapidity in defining the trigger criteria, new false triggers would still happen.

What are the limitations of the service?

The service does not pretend to report all the felt earthquakes. It only detects felt earthquakes in countries where a sufficient number of eyewitnesses naturally visit the EMSC website after the ground has shaken. In practice, the service currently performs well in Europe. However, in areas where the level of seismicity is low and the EMSC awareness is not as high, such as Scandinavia, there are not as many eyewitnesses to cause a significant traffic surge after a felt earthquake.

Are there any privacy issues associated with this service?

No. No personal data is used, only the IP locations. The accuracy is at the city level and individual visitors cannot be identified through their IP addresses. IP locations are determined at the EMSC premises thanks to a database provided by our partner Digital Element. IP addresses are not transferred to third parties.

Can one expect even faster detection of felt earthquakes?

Yes. The rapidity of the detection is directly linked to the visibility of the EMSC website which has been continuously improving since 2004. The results are already visible: In a 2008 paper*, we were reporting triggers within three to five minutes. Detection within less than one minute is likely to become a standard in the future.

Can one expect an extension of the geographical coverage of the service?

Yes. The geographical coverage of the service is directly linked to the local level of awareness of the EMSC website. With the growing and expanding knowledge of our services, the geographical coverage of the service will naturally extend to other areas.

What are the next steps?

Our current research shows that it should be possible not only to detect the felt earthquakes but also to characterize the actual level of shaking in the different localities and map the extent of the damaged areas. We hope to ultimately publish an automatic map of an earthquake’s effects within a few minutes of its occurrence.

* R. Bossu, Mazet-Roux, G., Douet, V., Rives, S., Marin, S. and M. Aupetit, Internet users as seismic sensors for improved earthquake response. EOS, Transactions, Vol. 89 (25), 17 June 2008, pp. 225-226

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Scientific references