WAVEFORMS	Subroutines to define some wavelets for modeling of seimic
		data.
	
ricker1_wavelet		Compute the time response of a source function as
			a Ricker wavelet with peak frequency "fpeak" Hz.	

ricker2_wavelet		Compute a Ricke wavelet with a given period, amplitude
			and distorsion factor

akb_wavelet 		Compute the time response of a source function as
			a wavelet based on a wavelet used by Alford, Kelly, 
			and Boore.

spike_wavelet		Compute the time response of a source function as
			a spike.	

unit_wavelet 		Compute the time response of a source function as
			a constant unit shift.	

zero_wavelet		Compute the time response of a source function as
			zero everywhere.	
Function Prototypes:
void ricker1_wavelet (int nt, float dt, float fpeak, float *wavelet);
void ricker2_wavelet (int hlw, float dt, float period, float ampl, 
	float distort, float *wavelet);
void akb_wavelet (int nt, float dt, float fpeak, float *wavelet);
void spike_wavelet (int nt, int tindex, float *wavelet);
void unit_wavelet (int nt, float *wavelet);
void zero_wavelet (int nt, float *wavelet);
Authors: Tong Fei, Ken Larner