What is the P wave 'shadow zone' and what
does it mean if you are located in that zone?
- When an earthquake occurs, seismic waves
radiate from the focus. These seismic waves tell us a great
deal about the internal structure of the Earth.
The P-wave shadow zone is a region that extends from 104 degrees
to 142 degrees from the epicenter of an earthquake and is marked
by the absence of P waves. Beyond 104 degrees the p-wave amplitudes
diminish as they are refracted into the core and emerge at epicentral
distances beyond 142 degrees where they are concentrated. Since
waves are detected, then not, then reappear again, something
inside the Earth must be bending the P waves. The P-wave shadow
zone is due to the refraction of seismic waves in the liquid
outer core.
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