SOUNDS OF SEISMOLOGY:
Earthquakes in Sumatra: demonstration of magnitude with sound

The largest earthquake that has and probably will occur in your lifetimes has already happened, in 2004 in Sumatra. This region is very active, seismically... so we compare three earthquakes from approximately the same fault, with very different magnitudes, about M5, M7 and M9, to demonstrate the meaning of magnitude. Since we cannot use volume to demonstrate these differences in a true way, we use the duration of the ringing of the Earth after each earthquake. The larger the magnitude, the farther the waves travel and the longer the earth is ringing.




Northern Sumatra, Mw 7.2, 2002/11/2 1:26 GMT
with Mw 5 aftershock
12 hrs at 20 sps

40 k

56 k

64 k


SYNTHETIC calculation of waves from same source
4 k, synthetic calculation

8 k, synthetic calculation


Sumatra-Andaman Islands Great Earthquake, 2004/12/26
Mw 9.0, Depth 28 km.
the earthquake that produced the catastrophic tsunami.

The following movies (made by Vala Hjorleifsdottir, when she was at the Seismological Laboratory, CalTech) show the surface wave propagation near the source:
Note that the duration of the rupture is about 12 minutes (HUGE!).



and a movie of the surface waves propagating around the globe:


Sounds:
24 hrs of data, 20 sps

40 k

56 k



coming soon: Sumatra M9.0, three weeks of data... !!!!!