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Unformatted text preview: Understanding Seismic Events Ch.3 of “Elements of 3D Seismology” by Chris Liner Or “ How to tell the difference between a reflection, a refraction a diffraction from one or more buried layers” Outline1 • Full space, half space and quarter space • Traveltime curves of direct ground and air waves and rays • Error analysis of direct waves and rays • Constantvelocitylayered halfspace • Constantvelocity versus Gradient layers • Reflections • Scattering Coefficients Outline2 • AVA Angular reflection coefficients • Vertical Resolution • Fresnel horizontal resolution • Headwaves • Diffraction • Ghosts • Land • Marine • Velocity layering • “approximately hyperbolic equations” • multiples A few NEW and OLD idealizations used by applied seismologists….. “Acoustic waves can travel in either a constant velocity full space, a halfspace, a quarter space or a layered halfspace” IDEALIZATION #1: XX zz A full space is infinite in all directionsX z A halfspace is semiinfinite XX z A quarterspace is quarterinfinite X Outline • Full space, half space and quarter space • Traveltime curves of direct ground and air waves and rays • Error analysis of direct waves and rays • Constantvelocitylayered halfspace • Constantvelocity versus Gradient layers • Reflections • Scattering CoefficientsX z A direct air wave and a direct ground Pwave ….. X A direct air wave and a direct ground Pwave ….. A direct air wave and a direct ground Pwave ….. A direct air wave and a direct ground Pwave ….. The data set of a shot and its geophones is called a shot gather or ensemble . Vp air Vp ground ray wavefront geophone Traveltime curves for direct arrivals Shotreceiver distance X (m) Time (s) Traveltime curves for direct arrivals Shotreceiver distance X (m) Time (s) Airwave or air blast (330 m/s) Direct ground Pwave e.g. 1000 m/s dT dT dx dx Outline • Full space, half space and quarter space • Traveltime curves of direct ground and air waves and rays • Error analysis of direct waves and rays • Constantvelocitylayered halfspace • Constantvelocity versus Gradient layers • Reflections • Scattering Coefficients Error analysis of direct waves and rays See also http://www.rit.edu/cos/uphysics/uncertainties/Uncer taintiespart2.html by Vern Lindberg • Liner presents the general error analysis method with partial differentials....
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This note was uploaded on 01/06/2012 for the course GEO 4068 taught by Professor Lorenzo during the Fall '10 term at LSU.
 Fall '10
 Lorenzo

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