  We derive average radial gradients in the dust attenuation towards HII
regions in 609 galaxies at z~1.4, using measurements of the Balmer decrement
out to r~3kpc. The Balmer decrements are derived from spatially resolved maps
of Halpha and Hbeta emission from the 3D-HST survey. We find that with
increasing stellar mass (M) both the normalization and strength of the gradient
in dust attenuation increases. Galaxies with a mean mass of <log(M)> = 9.2Msun
have little dust attenuation at all radii, whereas galaxies with <log(M)>=
10.2Msun have dust attenuation toward Halpha A(Halpha)~2mag in their central
regions. We parameterize this as A(Halpha) = b + c log(r), with b = 0.9 + 1.0
log(M10), c = -1.9 - 2.2 log(M10), r in kpc, and M10 the stellar mass in units
of 10^10Msun. This expression can be used to correct spatially resolved
measurements of Halpha to radial distributions of star formation. When applied
to our data, we find that the star formation rates in the central r<1kpc of
galaxies in the highest mass bin are ~ 6 Msun/yr, six times higher than before
correction and approximately half of the total star formation rate of these
galaxies. If this high central star formation rate is maintained for several
Gyr, a large fraction of the stars in present-day bulges likely formed in-situ.
