Temporal change in mass eruption rate estimated from co-eruptive seismograms during 2014–2018 eruption at Sinabung Volcano, Indonesia

Abstract An effusive eruption occurred at Sinabung volcano, Indonesia, from December 2013 to February 2018. The eruption peaked with violent pyroclastic density currents (PDCs) and a lava flow in the first three months of 2014 and then gradually declined. After the lava flow activity ceased, in October 2014, minor PDCs repeated and Vulcanian eruptions started in August 2015. For estimating the erupted mass from individual PDCs and Vulcanian eruptions after October 2014, a simple but robust method that uses the co-eruptive seismic energy associated with PDCs and Vulcanian eruptions is proposed. Empirical relationships between co-eruptive seismic energies and masses are obtained for both eruption types. PDC masses are estimated using numerical simulation, where the inundation area is determined based on the observed runout distance. For Vulcanian eruptions, the ash mass eruption rate is calculated using the method of Woodhouse et al. [1] considering wind velocity. The estimated PDC masses range from 1 × 10 4 to 1.5 × 10 9 kg. Ash masses from Vulcanian eruptions range from 2 × 10 1 to 2 × 10 8 kg, representing the first quantitative estimates of Vulcanian ash mass during the 2014–2018 Sinabung eruption. The uncertainties are approximately 60% for PDCs and 30% for Vulcanian eruptions and may reflect the discrete nature of the observational data, seismic limitations, and topographic effects. PDC masses generally extend to higher values, although the two ranges overlap. The total erupted mass from October 2014 to February 2018 is estimated to be 3.6 × 10 10 kg, where the Vulcanian ash mass is only 8% of the total. The mass eruption rate from March 2014 to February 2018 shows an exponential decay throughout the entire magmatic eruption. The appearance of Vulcanian eruptions beginning in August 2015 may be related to a gas pocket formed by the repeated ascent and arrest of magma in the conduit that behaves as a Bingham fluid.