Scientist-Musician Digs Earthquakes

By MATTHEW FORDAHL
..c The Associated Press

  
SAN FRANCISCO (AP) - The hills are alive with the sound of music - and so are 
the Earth's valleys, mid-ocean ridges and volcanoes. 

Earthquake waves that topple buildings, raise mountains and split the ground 
have long been used to study tremors and the structure of the Earth. Now, 
they're being turned into sound to make truly hard-rock music that can help 
teach seismology. 

Though seismic waves make no noise on their own, their motions as recorded by 
seismometers can be sped up to produce sounds, says Andrew Michael, a 
trombone-playing seismologist at the U.S. Geological Survey and composer of a 
quake quartet. 

``The music came from a concept of how the Earth strains to create 
earthquakes and earthquakes providing a backdrop to civilization,'' he said. 
``The general population is almost completely unaware until there's a very 
large earthquake.'' 

Michael's piece for trombone, cello, vocalist and earthquake is about the 
strain that leads to quakes as well as their impact on society. It premiered 
last month at the annual meeting of the American Geophysical Union. 

The two-minute quartet begins with a trombone and cello glissando punctuated 
by the thundering roars generated from the 1992 Landers, Calif., earthquakes. 
The sliding noise represents the buildup in the Earth before a quake strikes. 

A jazzy movement, which borrowed from a Bach cello sonata, is interrupted by 
the quakes' thunder-like rumbling. The glissando then returns and the piece 
ends with the thud of a big quake. 

``It made a good percussion track,'' said Stephanie Ross, Michael's wife who 
sings the quartet's vocal line. She's also a researcher at the USGS in Menlo 
Park. 

Michael's interest in music and earthquakes began in 1997, when he was 
preparing a lecture on earthquake waves trapped in fault zones. It struck him 
that the situation was similar to sound waves trapped and vibrating inside a 
trumpet. 

The parallels didn't work for that lecture because of the fleeting nature of 
earthquake waves in a small area. ``But I started thinking more about the 
comparisons and decided to do a whole lecture on the analogy,'' he said. 

Seismic waves are much more complex than sound waves, but both transmit 
energy from a source through a path like the ripples from a pebble dropped in 
a pond or a spring compressing or decompressing. 

Earthquake waves move too slowly to make audible sound, though many people 
hear the rumbling of objects being shaken. To actually hear a quake, Michael 
speeds up recordings of their waves. 

Seismograms - the squiggly line graphs that show ground motion - measure 
several types of waves. To become sound, the entire range of a quake's motion 
is reduced to the in-out motion of a speaker, which vibrates to make sound. 

``We are playing fast and loose by taking the whole seismogram and turning it 
all into compressions and noncompressions,'' he said. ``But it works well 
enough.'' 

And it has scientific value. 

``It puts us in the position of being the music critic to the Earth,'' said 
Michael, a trombonist since childhood. 

By listening, scientists can tell how much a fault slipped. Smaller faults, 
like small musical instruments such as trumpets, produce higher frequency 
waves than longer faults, or big instruments like tubas. 

So a magnitude-6.3 quake from a small fault has a higher pitch than a 
magnitude-6.5 quake generated along a larger fault. 

Quakes recorded from a distance have a much deeper sound resembling thunder. 
Closer quakes, on the other hand, sound more like a gunshot. 

The reason? High frequency waves dissipate more quickly over distance, 
leaving only a low rumble. It's not unlike the boom heard through the wall 
from a neighbor's stereo. The higher-pitch lyrics and melodies don't travel 
as far. 

Michael so far has presented his lecture less than a dozen times at 
universities and scientific conferences. He hopes someday to make it 
available on video. 

``There's actually been a good reaction from the general public,'' he said. 
``It's spoken to different people in different ways. People are actually 
learning some seismology and music.'' 

EDITOR'S NOTE: Sounds generated from earthquakes are available on the World 
Wide Web at http://quake.wr.usgs.gov/more/listen/ 

AP-NY-01-23-00 1202EST

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