  Resonant Shattering flares (RSFs) are bursts of gamma-rays expected to be
triggered by tidal resonance of a neutron star (NS) during binary inspiral.
They are strongly dependent on the magnetic field strength at the surface of
the NS. By modelling these flares as being the result of multiple colliding
relativistic shells launched during the resonance window, we find that the
prompt non-thermal gamma-ray emission may have luminosity up to a few
$\times10^{48}\text{ erg/s}$, and that a broad-band afterglow could be
produced. We compute the expected rates of detectable RSFs using the BPASS
population synthesis code, with different assumptions about the evolution of
surface magnetic field strengths before merger. We find the rate of detectable
RSFs to be $\sim 0.0001-5$ per year for BHNS mergers and $\sim 0.0005-25$ per
year for NSNS mergers, with the lower bound corresponding to surface-field
decay consistent with magneto-thermal evolution in purely crustal fields, while
the upper bounds are for systems which have longer-lived surface magnetic
fields supported by flux frozen into the superconducting core. If some of the
observed SGRB precursor flares are indeed RSFs, this suggests the presence of a
longer-lived surface field for some fraction of the neutron star population,
and that we could expect RSFs to be the most common detectable EM counterpart
to GW detections of BHNS mergers. The non-detection of a RSF prior to
GRB170817A provides an upper bound on the magnetic fields of the progenitor NSs
of $B_{\rm surf}\sim 10^{13.5} \text{ G}$.
