Temporal Change in Mass Eruption Rate Estimated from Co-eruptive Seismograms during 2014-2018 Eruption at Sinabung Volcano, Indonesia

An effusive eruption occurred at Sinabung volcano, Indonesia, from December 2013 to February 2018. The eruption peaked with violent pyroclastic density currents (PDCs) and 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 used 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 eruptions types. PDC masses are estimated using numerical simulation, where the inundation area is determined based on the observed runout distance. For Vulcanian eruptions, ash mass eruption rate is calculated using the method of Woodhouse et al. considering wind velocity. The estimated PDC mass ranges from 2×10 ⁵ kg to 7×10 ⁷ kg. Ash masses from Vulcanian eruptions ranges from 8×10 ² kg to 7×10 ⁶ kg, an order of magnitude smaller than that for PDCs. The total erupted masses from October 2014 to February 2018 is estimated to be 2.54 ×10 ¹⁰ kg, with Vulcanian ash mass is only 1.5% of the total. The mass eruption rate from March 2014 to February 2018 shows an exponential decay throughout the entire magmatic eruption. Vulcanian eruptions appearance from August 2015 may be related to a gas pocket formed by the repeated ascent and flow arrest of magma behaving as a Bingham fluid in the conduit.