# Elastic impedance

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Elastic impedance is a pseudo-property or seismic attribute developed by Connolly in 1998[1] in 1999 [2]. It is a generalization of acoustic impedance for non-normal angles of incidence To invert a vertical-offset (normal incidence) seismic trace, acoustic impedance is used directly from well log bulk density and P-velocity. However, for offset traces, an equivalent of the acoustic impedance can be used to calibrate the non-zero-offset seismic reflectivity.

## Theory

${\displaystyle EI(\theta _{P})=\alpha ^{a}\beta ^{b}\rho _{B}^{c}}$

${\displaystyle a=1+tan^{2}\theta _{P}}$

${\displaystyle b=-8Ksin^{2}\theta _{P}}$

${\displaystyle c=1-4Ksin^{2}\theta _{P}}$, where 'K' is usually set to the average value of ${\displaystyle (\beta /\alpha )^{2}}$ over the log interval of interest,

<references>Connolly, P., 1998, Calibration and inversion of non-zero offset seismic: 68th SEG, New Orleans, USA, Expanded Abstracts, 182-184.<\references> <references>Connolly, P., 1999, Elastic Impedance, 'The Leading Edge', 18 (4), 438-352.<\references>