Blazars, a subclass of AGN jets, show extreme flux variability across the electromagnetic spectrum from radio to gamma-rays. A challenge to theoretical interpretation is the rapid flux variability at GeV energies, which implies an origin from ultra-compact emission regions (< sub-pc). The exact location of the gamma-ray emitting region within the AGN is also controversially discussed. The prime objective of my project is, therefore, to identify such gamma-ray emitting regions and constrain their physical conditions using multi-epoch high-resolution VLBI imaging.

In this talk, I will present a case study of the gamma-ray flaring events which occurred in the compact blazar 2013+370 during 2002-2012. Preliminary analysis of gamma-ray light curves sampled by the Fermi space satellite and multi-epoch VLBI imaging from 15 to 86 GHz reveal the following: (a) the flaring events are clearly correlated with the jet kinematics on VLBI scales and (b) with the flux density of the VLBI core. A tentative interpretation of our results will be presented.