Alternatives to SP Triangulation Hubenthal M Taber M An Inverse Problem W e know the end product arrival times W e have a velocity model for Earth and we want to calculate the original ID: 631362
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Slide1
How DO they actually locate earthquakes?
Alternatives to S-P Triangulation
Hubenthal, M. Taber, M.Slide2
An Inverse Problem
W
e
know the end product; arrival times We have a velocity model for Earth and we want to calculate the original eventLocationOrigin time
Forward Problem = Model parameters → Data
Inverse Problem = Data → Model parametersSlide3
The bisector method
P
arrivals are much easier to
pick Assumes an extremely simple velocity model
Which station of this record section was closest?
1
2
3
4
5
6Slide4
Bisector Steps
Mark and measure
path
between TATO/WAKEFind midpoint of pathDraw bisector perpendicular to path
Label Bisector with station namesDetermine which side of the bisector was close to the event.
Repeat with TATO/YAK
Repeat with WAKE/YAK
Repeat with additional stations of your choiceSlide5
Path
Bisector
TATO
WAKE
XSlide6
Bisector Steps
Mark and measure
path
between TATO/WAKEFind midpoint of pathDraw bisector perpendicular to path
Label Bisector with station namesDetermine which side of the bisector was close to the event.
Repeat with TATO/YAK
Repeat with WAKE/YAK
Repeat with additional stations of your choiceSlide7
SolutionSlide8
Compare to regional seismicitySlide9
Earth is Complex
PREM ModelSlide10
Earth is Complex
PREM ModelSlide11
Solution to complexity
Iterative approach
Solution through the model provides result
Result is run back through the model to see if it matches the observations (forward problem)Differences used to refine the model to compute a new solution. Process continues until some condition is metSlide12
In realityMore data
More
complex
modelsIterative approach