kernel_fresnel_2d Sensitivity kernel for amplitude and first arrival
 
  Call:
    [kernel_t,kernel_a,P_omega,omega]=kernel_fresnel_2d(v,x,y,S,R,omega,P_omega);
 
 
  Based on Liu, Dong, Wang, Zhu and Ma, 2009, Sensitivity kernels for
  seismic Fresenl volume Tomography, Geophysics, 75(5), U35-U46
 
  See also kernel_fresnel_monochrome_2d
 
  Run with no argument for an example.