Subject: corvid quake conniptions
Date: Mar 2 15:00:15 2001
From: Fred Sharpe - fsharpe at sfu.ca



When the earthquake hit, I was visiting some friends in the farm country
on the Saanich Peninsula just north of Victoria. Having just finished up
school, I was laying in bed wondering what to do with my life (I had come
to the conclusion that I would was going to stay in bed forever).

Louise was showering in the bathroom in the next room. One of my friends
decided to take the garden hose and slip it through the bathroom and give
her a good soaking with freezing water. At the same moment earthquake hit,
she gave blood curdling screams in response to the cascade of cold water.
I was pretty confused by the chain of events, but was sure that the world
was ending. I decided to remain hidden under the covers. Blankets are
well know to provide protection from monsters and I figured they would also
provide some immunity from Armageddon

>From this vantage point, I didn't notice any wildlife having a quake
related conniption. However, I am intrigued by the many Tweeter
observations of animals reacting to the quake. The most important
questions are 1) what signals does the tremor produce and 2) what sensory
mode are the animals using to detect the signals?

I know little about sound transmission through land masses. However, my
experience in marine mammal acoustics suggests that there could be a sound
wave that travels in advance of the tremor. When a whale breaches, it
sends a loud, fast moving sound wave underwater. However, the actual wake
from the impact travels much slower, and reaches the observer much later.

Could a similar phenomenon be occurring with earthquakes? The Olympia
quake appeared to be a largely silent earthquake. However, there could
have been an advance acoustic wave that traveled in front of the tremor.
This sound wave may occur at frequencies above or below human hearing, or
simply be to quiet for humans to deect. If this was the case, then the
time delay from when dogs start howling, and humans feel the tremor should
increase with distance from the epicenter (sorta like the time delay with
lighting and thunder). In addition, only acoustically sensitive animals
should react in advance of the tremor. Its seems that most birds such as
crows and gulls reaced to the slower moving dispacement waves that human
can feel. It would interesting to see if observations support these
notions. In the mean time, I'm going back to bed.

Fred Sharpe
Port Ludlow Wa
fsharpe at sfu.ca


><>< <>< <>< <>< <>< <>< <"}}}}}}}><{
>Behavioral Ecology Research Group
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