Rotational misalignment of two stacked honeycomb lattices produces a moire pattern that is observable in scanning tunneling microscopy as a small modulation of the apparent surface height. This is known from experiments on highly-oriented pyrolytic graphite. Here, we observe the combined effect of three-layer moire patterns in multilayer graphene grown on SiC ($000bar{1}$). Small-angle rotations between the first and third layer are shown to produce a double-moire pattern, resulting from the interference of moire patterns from the first three layers. These patterns are strongly affected by relative lattice strain between the layers. We model the moire patterns as a beat-period of the mismatched reciprocal lattice vectors and show how these patterns can be used to determine the relative strain between lattices, in analogy to strain measurement by optical moire interferometry.
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