  In a recent paper [Phys. Rev. X 12, 031021], we reported experimental
observations of ``ultrastable'' states in a shear-jammed granular system
subjected to small-amplitude cyclic shear. In such states, all the particle
positions and contact forces are reproduced after each shear cycle so that a
strobed image of the stresses and particle positions appears static. In the
present work, we report further analyses of data from those experiments to
characterize both global and local responses of ultrastable states within a
shear cycle, not just the strobed dynamics. We find that ultrastable states
follow a power-law relation between shear modulus and pressure with an exponent
$\beta\approx 0.5$, reminiscent of critical scaling laws near jamming. We also
examine the evolution of contact forces measured using photoelasticimetry. We
find that there are two types of contacts: non-persistent contacts that
reversibly open and close; and persistent contacts that never open \yiqiu{and
display no measurable sliding}. We show that the non-persistent contacts make a
non-negligible contribution to the emergent shear modulus. We also analyze the
spatial correlations of the stress tensor and compare them to the predictions
of a recent theory of the emergent elasticity of granular solids, the Vector
Charge Theory of Granular mechanics and dynamics (VCTG) [Phys. Rev. Lett. 125,
118002, arXiv:2204.11811]. We show that our experimental results can be fit
well by VCTG, assuming uniaxial symmetry of the contact networks. The fits
reveal that the response of the ultrastable states to additional applied stress
is substantially more isotropic than that of the original shear-jammed states.
Our results provide important insight into the mechanical properties of
frictional granular solids created by shear.
