  The nearby radio galaxy M87 offers a unique opportunity for exploring the
connection between gamma-ray production and jet formation at an unprecedented
linear resolution. However, the origin and location of the gamma-rays in this
source is still elusive. Based on previous radio/TeV correlation events, the
unresolved jet base (radio core) and the peculiar knot HST-1 at >120 pc from
the nucleus are proposed as candidate site(s) of gamma-ray production. Here we
report our intensive, high-resolution radio monitoring observations of the M87
jet with the VLBI Exploration of Radio Astrometry (VERA) and the European VLBI
Network (EVN) from February 2011 to October 2012. During this period, an
elevated level of the M87 flux is reported at TeV with VERITAS. We detected a
remarkable flux increase in the radio core with VERA at 22/43 GHz coincident
with the VHE activity. Meanwhile, HST-1 remained quiescent in terms of its flux
density and structure at radio. These results strongly suggest that the TeV
gamma-ray activity in 2012 originates in the jet base within 0.03 pc
(projected) from the central supermassive black hole.
