= Double-couple radiation pattern
{title2=$A_P=2n_1n_2,\quad \boldsymbol A_S=(n_2,n_1,0)-2n_1n_2n$}
For the <seismic moment tensor> $M=e_1e_2^{\mathsf T}+e_2e_1^{\mathsf T}$, source differentiation of the outgoing <elastodynamic Green tensor> gives $A_P=n^{\mathsf T}Mn$ and $\boldsymbol A_S=(I-nn^{\mathsf T})Mn$. In the $x_1x_2$ plane the signed radial <P wave> and tangential <S wave> factors are $\sin2\phi$ and $\cos2\phi$. The full <S wave> magnitude squared is $n_1^2+n_2^2-4n_1^2n_2^2$.
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