Earthquake observation

In the event of an earthquake stress that has accumulated in the bedrock is suddenly released. This sends seismic waves in all directions from the epicenter. In the case of large-magnitude earthquakes the waves are strong and propagate long distances before they finally attenuate. A smaller earthquake generates weaker seismic waves.
Specific instruments are used to register the seismic waves. The instruments are located at different distances to the epicenter, and they record the arrival times of the wave phases. They are used to locate the earthquake.
Also people can notice the seismic waves as they pass by. Outdoors people may observe ground tremors, and indoors the shaking may have effects on objects. An individual person notices earthquake effects at a given place. If there are many observations from different places, it may become possible to determine the area of perceptibility.
Our aim is to collect information about the size of the areas where earthquakes of different sizes (magnitudes) are noticed and what effects they have. It would be great if as many persons as possible fill in the questionnaire on the web. It is also useful for us to receive information from sites where nothing was observed after an earthquake.
Collection of felt reports is a fully non-commercial activity.

 Background information