  The shear modulus of jammed frictional granular materials with the harmonic
repulsive interaction under an oscillatory shear is numerically investigated.
It is confirmed that the storage modulus, the real part of the shear modulus,
for frictional grains with sufficiently small strain amplitude $\gamma_0$
discontinuously emerges at the jamming transition point. The storage modulus
for small $\gamma_0$ differs from that of frictionless grains even in the zero
friction limit, while they are almost identical with each other for
sufficiently large $\gamma_0$, where the transition becomes continuous. The
stress-strain curve exhibits a hysteresis loop even for a small strain, which
connects a linear region for sufficiently small strain to another linear region
for relatively larger strain. We propose a new scaling law to interpolate
between the states of small and large $\gamma_0$.
