A211

Changes in Mass Eruption Rate during 2014-2018 Sinabung's Eruptive Period estimated using
Seismic Energy〇Vico L. IPMAWAN, Masato IGUCHI, Taishi YAMADA, Takeshi TAMEGURI

Introduction

farthest seismic station to avoid amplitude saturation.

Sinabung is a volcano located to the northwest ofLake Toba,

Sumatra,Indonesia. This

The total MER is obtained from the combination ofvolcano

MER of PDC and MER of Vulcanian events. To

reactivated after a hiatus of 1200 years (Iguchi et al.,calculate the MER of PDC, we assessed the empirical2012). The phreatic eruption on September 27, 2010,

relationship between the seismic energy of PDC and themarked the beginning of pre-magmatic activity, which

run-out distance from observer records. Then,continued until the end of December 2013. Eruption

separately, we conducted pyroclastic flow simulations

activity transitioned to fully magmatic in 2014, with(Yamashita and Miyamoto, 1993) by varying thehigh-intensity pyroclastic density currents (PDC)

volume to obtain the run-out distance. Using theoriginating from the lava dome that developed insimulation results, we evaluated the relationship

December 2013. PDC activity ceased on January 10,

between volume and run-out distance. To obtain the2014, followed by lava flow until mid-September 2014.

Mass from volume, a density value of 𝜌 = 1400 kg/m3

The lava dome regrew, and PDC activity resumed until

was used. To calculate the Mass Eruption Rate, the totalFebruary 2018. However, in August 2014, vulcanianmass of each event was divided by the duration ofactivity occurred, accompanied by a decrease in PDC

material ejection.

activity.

To determine the MER of Vulcanian events, weThe transition from non-Vulcanian to Vulcanianassessed the empirical relationship between seismicstyle is important for further study. A change in

amplitude and plume height. Subsequently, aneruption style implies a shift in disaster eruption

empirical relationship between mass eruption rate andmitigation strategies as well. Some researchers reported

plume height, based on a theoretical approach, wasthat change in eruption style can be controlled by Mass

obtained from Sakurajima (Iguchi et al., 2022)

Eruption Rate (MER) as a crucial parameter (Melnikand Sparks, 2005) andas an indicator of eruption

Results and Discussion

style changes (Cashman, 2004; Gonnermann andThe total MER is obtained by summing the MER ofManga, 2013; Kozono et al., 2013). We estimate thePDC and vulcanian events, as presented in Fig. 1c. The

total MER, both from PDC and Vulcanian events, fromhighest MER value is 0.43 megaton/day, which

October 2014 to February 2018. Changes in the total

occurred in early October 2014. Then, the MER rate

MER over time are discussed in relation to changes indecreased to 0.2 megaton/day in mid-December 2014

eruption style.

to March 2015. As it enters the vulcanian period, MER
becomes 0.15 megaton/day. MER remains relatively

Data and Method
We analyze PDC and Vulcanian events from theconstant at 0.15 megaton/day until June 2016.
Afterward, MER gradually decreases, reaching a value

of 0.12 megaton/day at the end of the calculation onperiods. This may lead to the interpretation thatFebruary 28, 2018.

changes in MER can control the transition in eruption

We compared the discharge rate of PDC and volcanic
ash with calculations from Nakada et al. (2019),
CVGHM staff and Kriswati and Solikhin (2020).
Nakada et al. (2019)style from lava dome growth with PDC to lava dome
growth with PDC and vulcanian eruptions.
A significant difference of discharge rate occurred in

calculations are based on

October 2015 between the previous and this study. It

measurements using a Laser Distance Meter andmay be due to the inclusion of vulcanian ashfall in thesatellite images, while CVGHM staff measures thedischarge rate calculation. It is also worth noting thatdischarge rate using the growth of lava dome by using

the MER from vulcanian events has been increasing

Laser Distance Meter. The comparison results are

since December 2015. This increasing MER would

shown in Fig. 1d. Overall, the volume rate trend fromcertainly affect the accuracy of hot spot detection using

this study matches the results of previous studies.

the MODIS method. Thus, the differences in

Examining the declining trend, the MER graph can becalculations may be attributed to the increased

divided into two periods: one with relatively high MER

vulcanian activity, as explained by Kriswati and(>0.15 megatons per day) and one with low MER

Solikhin (2020). Another explanation may be attributed(<0.15 megatons per day). This change corresponds toto irregularity of lava dome measurement.

the boundary between the non-vulcanian and vulcanianFig. 1. Cumulative Mass of a) PDC event and b) vulcanian event, c) total MER based on seismic
calculation, d) comparison of log discharge rate from this study with the previous studies.