Category Archives: Magnitude

7 years in Japan (Tohoku Eq, 2011)

This movie shows earthquakes from Japan larger than Magnitude 3.5 (more than 10,000 events), in the years between Jan. 1, 2008 – Dec. 31, 2014. The Magnitude 9.0 Tohoku-oki earthquake was on March 11, 2011 (note the title bar in the movie says 2012, which is incorrect!). This is the same time window and distance in latitude (but not longitude) as the movie on the Caribbean and Haiti M7.0 earthquake: Haiti: The dot size is (non-linearly) proportional to magnitude and the color is proportional to depth according to these rules:
Key: .
The sound is generated by adding to the sound track tiny earthquake sounds, as described by that link.
The data comes from the ANSS catalog of the US Geological Survey, accessible from here:

Ben Holtzman, Douglas Repetto, Jason Candler, Nolan Lem. CC licence .

Seismicity in Nepal

We have just produced a movie of seismicity (earthquake patterns in space and time) in the region of the Himalaya centered on Nepal, to demonstrate the context for the recent M7.8 earthquake on April 25, 2015, that had terrible consequences for many many people.¬†This movie represents 42 years of seismicity in the Nepal region, with all earthquakes above M3.5 (from the ANSS catalog). The size of each dot represents the magnitude, while the color scales with depth; blue indicates shallow upper crust, increasing to purple, then red and then orange (the “Key” is here ). The orange earthquakes are > 50 km, and are mostly in the subducting plate. The lack of earthquakes to the west of the April 25th, 2015 earthquake and its aftershocks indicates a potentially elevated risk in that region. The sounds are generated from a library of tiny earthquake sounds (“granules”) that we created.

Magnitude 9 Tohoku Earthquake (March 11, 2011): SPECFEM with sound

This is a recent movie we put together using simulations of the Tohoku earthquake with sound from broadband seismometers (8 in a great circle mixed to stereo). We have been experimenting with ways to render the SPECFEM3D simulations to separately visualize surface and body waves, relatively low and high frequency parts of the spectrum respectively, to correspond to the sounds that are given low- and high-pass filters. So the two renderings shown here are from the same seismic data and the same simulation, just filtered differently. Matt has been developing methods in “yt” to render complex migrating wave fronts, which is an interesting visualization problem. This is our first presentation of these movies, with lots of improvement to come.¬†For best results, view the movie at full screen and use big headphones.