The National Institute of Geophysics and Volcanology (INGV) has created the video of the animation of the propagation of seismic waves on the earth's surface generated by Mw 6.5 earthquake at 07.40 on 30 October 2016 which involved Central Italy.
Animation is necessarily preliminary as the details of the breaking process will be known only in the next few days which, for events of this magnitude, are fundamental for an accurate simulation of wave propagation. Once analyzed they will be included in a higher resolution animation.
The color scale is eight times higher than the shakemovie made for the earthquake of August 24, 2016.
Waves in blue indicate that the ground is moving rapidly downwards, those in red indicate that the ground is moving upwards. The color intensity is higher for faster vertical shifts.
Each second of the animation represents one second in real time. The first 2 minutes starting from the origin of the seismic event are represented.
This is not an artistic animation but the solution of the equations describing the propagation process.
The speed and amplitude of seismic waves depend on the characteristics of the seismic source, the type of soil they pass through and also on the topography. They, therefore, they do not propagate uniformly in space and, consequently, places located at the same distance from the epicenter are affected by the earthquake in a completely different way. In this case it can be observed, for example, that the waves propagated with greater intensity and for longer towards the Adriatic regions, towards Lazio and southern Tuscany.
Technical detail:
to reduce calculation times and given the limited current knowledge of the details of the subsoil, the Italian-scale simulation of this animation is relatively "low-frequency", that is, it displays the frequencies of the waves up to 0.25 Hz. This means that the front of The wave "interacts" with objects the size of 2/4 km. The local seismic response is therefore limited to the effects of geological structures of this size. By increasing the frequency content, smaller details and, for example, amplification due to sediments would be highlighted.
To improve the visualization of waves away from the epicenter, the color scale is saturated at 0.08 m/s: all values above 0.08 or below -0.08 have the same dark red – dark blue color, respectively.
edited by Emmanuel Casarotti e Federica Magnoni (INGV).