Yes, KM2DEG works:
lon=-71
lat=51
gmt grdmath -Rd -I1 $lon $lat SDIST KM2DEG = dist.grd
gmt psbasemap -R -JE-71/-51/18.0 -B20 -P -K > event_map.ps
gmt pscoast -R -J -Dl -B -S255 -G200 -W -A5000/1/4 -O -K >> event_map.ps
gmt grdcontour -J dist.grd -A20+s10+p1+g240 -Glz-/z+ -C20 -O >> event_map.ps