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Summary Different kinds of seismic sources Green’s function and Representation Theorem GFs for several important cases Acoustic, homogeneous whole space, explosion Elastic homogeneous whole space, point forces
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Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Mar 13, 2019

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Page 1: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Summary

•  Different kinds of seismic sources

•  Green’s function and Representation Theorem

•  GFs for several important cases –  Acoustic, homogeneous whole space, explosion

–  Elastic homogeneous whole space, point forces

Page 2: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Stokes, 1849

Page 3: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Earthquake as shear dislocation

Page 4: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Difficulties for “Internal” Sources

•  Wave equation not satisfied everywhere –  Discontinuity of displacement

–  Boundary conditions unknown

•  Kinematic description –  Distributed slip along fault, u(x, t)

Page 5: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

1920s~1960s

Can we find body forces that are equivalent to earthquake faulting, in terms of producing the same seismic responses everywhere?

YES!!!

Page 6: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Seismic Moment Tensor

Page 7: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Moment and Moment Rate Function

Page 8: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Response for a force couple

Page 9: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Displacement due to M0(t)

Page 10: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Radiation Pattern

Page 11: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s
Page 12: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s
Page 13: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s
Page 14: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s
Page 15: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Displacement due to M0(t)

Page 16: Different kinds of seismic sources Green’s function and ...web.gps.caltech.edu/classes/ge162/Ge162_Slides_March1st.pdf · Summary • Different kinds of seismic sources • Green’s

Static deformation