The itype argument in lamb.

• itype=1: The vertical and horizontal ground displacement will be computed and output in files lambv.seg and lambh.seg, respectively. The source function is a displacement step function.
• itype=2: This may be viewed in either of two ways. The derivative of a step function is an impulse function, and itype=2 is the derivative with respect to time of the itype=1 case. Thus, this may be viewed as the ground displacement for an impulse source function. Alternatively, this can also be viewed as the ground particle velocity for a source step function.
• itype=3: The source function is a single degree of freedom dampened resonator (exponentially decaying sinusoid wavelet, ground displacement function). The source is described by the sfreq and sdamp parameters. The output signals are ground displacements.
• itype=4: The source function is the same as itype=3, but the signals have been differentiated with respect to time. Thus, the output signals may be viewed as ground particle velocity for the itype=3 source.
• itype=5: This option switches the output signal from the actual ground motion to the motion of a geophone element (which is modeled as a single degree of freedom dampened oscillator bonded to the half-space at the surface). The geophone is described by the gfreq and gdamp parameters.
• itype=6: The itype=5 option with the output signal differentiated with respect to time. The output is the geophone element velocity. This case corresponds to the voltage that would be recorded by a velocity geophone.
• itype=7: The output signal is the source displacement function corresponding to itype=3, at the point of source application. If you have run a case with itype=3, this is the source wavelet.
• itype=8: The particle velocity of the source function at the point of application. This corresponds to itype=4 source wavelet.
• itype=9: This is like itype=7, with a geophone bonded at the source point. This is the displacement source wavelet as seen from the motion of a modeled geophone element.
• itype=10: This is like itype=8, with a geophone bonded at the source point. This is the particle velocity of the source wavelet as seen from the particle velocity of a geophone element bonded to the source point.