Ambient Seismic Noise:
What we can learn from
what we can’t feel
Celeste Labedz
Massachusetts Institute of Technology
Incorporated Research Institutions for Seismology
Summer Internship 2014
What can ambient seismic
noise give us?
• Clues about the inside of the earth
– A “telescope” for looking down
• Earth’s structure
– Earth’s history
– Earth’s hazards
wikipedia.org
geo.arizona.edu
What does “seismic” even mean?
• Earthquakes!
• Movement of waves through the earth
– Big waves
– Little waves
• Ambient seismic noise
How do we get ambient
seismic noise?
• Seismometers
• …LOTS of seismometers
usarray.org
How do we turn ambient seismic
noise into something we can use?
• Correlation between stations
wikipedia.org
• Analyzing the correlations
A plot of correlations:
How does seeing waves let us see
inside of the earth?
• Seismic waves bend and bounce
– Different paths
– Different times
aeic.alaska.edu
The Big Idea:
• Look at the arrival times of seismic waves
• Figure out the paths they took
• Turn the paths into a model of the inner
structure of the earth
• Use the model to observe layers,
subducted plates, hazard zones, and more