Volcán Popocatépetl has been erupting semi-continuously since 1994. During this period CENAPRED (Centro Nacional de Prevención de Desastres) has operated a deformation monitoring network consisting of 4 tiltmeters, 7 GPS stations and periodic EDM measurements. 
There have been no observations of long term deformation of Popocatépetl above background tectonic rates in the GPS network, although there may be some small short period transient signals (Cabrol-Cano et al., 2008). This has been supported by InSAR studies, which have also failed to detect deformation at a rate greater than 0.5 cm/year (Pinel et al., 2011, Chaussard et al., 2013).
The conclusion from published deformation studies is that the current eruptive phase of Popocatépetl is supplied by a network of deep rooted conduits rather than a shallow magma chamber. The volcano is thought to behave as a semi-open system, such that significant pressure build up does not occur (Cabrol-Cano et al., 2008).