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How DO they actually locate earthquakes?

How DO they actually locate earthquakes?. Alternatives to S-P 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 event Location Origin time.

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How DO they actually locate earthquakes?

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  1. How DO they actually locate earthquakes? Alternatives to S-P Triangulation Hubenthal, M. Taber, M.

  2. An Inverse Problem • We know the end product; arrival times • We have a velocity model for Earth and • we want to calculate the original event • Location • Origin time Forward Problem = Model parameters → Data Inverse Problem = Data → Model parameters

  3. The bisector method • P arrivals are much easier to pick  • Assumes an extremely simple velocity model 3 1 5 2 6 4 Which station of this record section was closest?

  4. Bisector Steps • Mark and measure path between TATO/WAKE • Find midpoint of path • Draw bisector perpendicular to path • Label Bisector with station names • Determine which side of the bisector was close to the event. • Repeat with TATO/YAK • Repeat with WAKE/YAK • Repeat with additional stations of your choice

  5. Bisector TATO WAKE X Path

  6. Bisector Steps • Mark and measure path between TATO/WAKE • Find midpoint of path • Draw bisector perpendicular to path • Label Bisector with station names • Determine which side of the bisector was close to the event. • Repeat with TATO/YAK • Repeat with WAKE/YAK • Repeat with additional stations of your choice

  7. Solution

  8. Compare to regional seismicity

  9. Earth is Complex PREM Model

  10. Earth is Complex PREM Model

  11. 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 met

  12. In reality • More data • More complex models • Iterative approach

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