IMPROVING THE UV CAMERA TECHNIQUE TO CORRELATED VOLCANIC SO2 EMISSION, SEISMIC, AND ACOUSTIC MEASUREMENTS AT PACAYA VOLCANO, GUATEMALA

SO₂ emission measurements are an important component of monitoring volcanic eruption processes. Limitations in the temporal resolution of measurements have made the goal of merging a gas flux record with other geophysical datasets with the aim of investigating subsurface processes elusive. In recent years, ground-based, ultraviolet (UV) digital cameras have improved upon previous methods of SO₂ observation by capturing a large portion of the plume in a single image. The UV digital camera can record at up to 1Hz, producing a data set that is more comparable with other monitoring techniques, allowing for a more precise record of SO₂ flux, and directly providing the plume speed.

Many monitoring advantages are gained by using this technique, but the accuracy and limitations require thorough investigation. The effects of some user-controlled parameters are addressed in this study. Laboratory and field experiments were conducted to clarify methodological consequences and quantify accuracy, including comparisons of SO₂ retrieval results from a coal power plant plume to direct sampling measurements. The results indicate that the UV camera retrieval compares favorably with direct sampling methods; that careful attention must be paid to exposure times; and that there is some latitude in the calibration cell conversion technique.

A multi-instrument field campaign was undertaken at Pacaya volcano, Guatemala to relate complementary high-temporal-resolution datasets. Between January 5 and January 9, 2008 SO₂ flux was recorded at Pacaya using the UV camera. These measurements were coincident with recordings from a temporary network of five broadband seismometers and five low-frequency microphones deployed between 0.6 and 3.1 km from the summit. The dominant event type recorded with the seimo-acoustic array was a small summit explosion characterized by simple “N”-wave acoustic signals. The locations, magnitudes, and timing of explosive events recorded by each monitoring method were evaluated for correlations with the SO₂ flux data. We present results of our efforts to evaluate the complementary data with respect to shallow conduit processes.