Santa Maria volcano has been erupting from the Santiaguito lava dome complex almost continually since 1922. The complex is formed of four vents, and current activity is concentrated at the Caliente Vent.
InSAR measurements of lava flows extruded between 2000 and 2009 were able to estimate a maximum flow thickness of 140 m and a maximum flow subsidence rate of 10 cm/yr at the thickest part of the flows (Ebmeier et al., 2012).
Campaign measurements of the dome, using particle image velocimetry from high resolution optical cameras and doppler shifted radar, have observed uplift of the surface of the dome (Sharff et al., 2012, Johnson et al., 2008). Dome uplift occurs 1-2 s before regular minor explosions and has a maximum amplitude of 50 cm. Ultra long period (ULP) seismic signals coincident with explosions are interpreted to be due to tilting of seismometers. Modelling of a Mogi tilt source suggests deflation of a reservoir located ~250 m below the summit and a volume loss of 125 to 1825 m³ (Sanderson et al., 2010).