program ex15

** Counting the number of quakes in a circle with a radius of rcircle
*		and centered at (flon0, flat0)


*** Define the parameters:

	flat0=35.0
	flon0=-96.0

	rcircle=30.0    !! circle radius in degrees

** Open the earthquake catalog file and compute the distance
*	from each quake to the center of the circle

*1980/01/01 16:41:45.70 -31.2110   58.7170  10.00  5.00
*123456789012345678901234567890123456789012345678901234
*         1         2         3         4         5

	nn=0   !! initiate the counter

	open(2,file='/home/sgao/compgeop/quakes.dat')

	do i=1,10000000
	read(2,21,end=222) iy, mo, id, ih, im, 
     &            flat, flon, dep, fmag
21	format(i4, 1x, i2, 1x, i2, 1x, i2, 1x, i2, 7x,
     &            f8.4, 1x, f9.4, f7.2, f6.2)


* Compute the distance (in degree) using the subroutine of distazsub

	call distazsub(flat,flon,flat0,flon0,distkm, distdeg,az,baz)

	if(distdeg.le.rcircle) nn=nn+1

	enddo
222	close(2)

	print*,'The number of quakes in the circle is ', nn

	stop
	end


** The code should be compiled using

*   gfortran ex15.f -m64 /home/sgao/subs/distazsub.f -o ex15.exe
*  or even better, a Makefile like (pay attention to the tab before gfortran):
*ex15.exe:ex15.f
*	gfortran ex15.f -m64 /home/sgao/subs/distazsub.f -o ex15.exe