New insights into volcanic system using physical model for vulcanian and gas burst explosions at Semeru Volcano, Indonesia.

Abstract:

Behavior of volatiles included in magma is well known to play an important role in volcanic activity. The buildup of gas overpressure is the driving force that leads to explosive eruption. During a sequence of eruptive activity, volcanoes display various styles of eruption with consequent wide variation in terms of magnitude and power. In Semeru volcano (Java, Indonesia), vulcanian eruptions explosively release large amounts of ash. They are preceded by about 200–300 s of inflation before the eruption suggesting volume expansion of the gas phase. In contrast, gas bursts, which rapidly emit water steam accompanied by explosive sounds, are preceded by about 20 sec of inflation before each emission. Tilt amplitudes increase with the magnitude of eruptions for both eruptive styles, but the two different inflation pattern suggest differences in the gas behavior within the same volcanic system. We develop a physical-based model to clarify how volatiles behavior affect the rate of inflation and magnitude observed at one given station. The availability of different scale of deformation related with the two different eruption styles allows us to perform a complete statistical analysis of physical parameters affecting the deformation. We show that it is possible to get reliable and quantitative information on the key physical controlling parameters, such as conduit geometry, magma and host rock properties, based on the large number of events recorded at one station.