PVMBG described activity at Sinabung during 24-31 January based on observations from a post in the Ndokum Siroga village, 8.5 km away. On 24 January dense white plumes rose as high as 1 km. During 25-26 and 28-31 January dense grayish-white plumes rose 0.1-1.5 km; on 27 January plumes rose 4 km. Each day pyroclastic flows traveled 0.5-4.5 km SE and S. Incandescent material was observed 0.2-1.5 km SE of the vent. Seismicity remained high, with constant tremor, hybrid earthquakes indicating a growing lava dome, and volcanic earthquakes. The number of low-frequency earthquakes continued to decrease. The Alert Level remained at 4 (on a scale of 1-4). Visitors and tourists were prohibited from approaching the crater within a radius of 5 km.

Badan Nacional Penanggulangan Bencana (BNPB) reported on 31 January that since activity at Sinabung had not increased residents from 16 villages outside of the 5-km radius were allowed to return to their homes. At 1030 on 1 February a large dome collapse generated pyroclastic flows that traveled 4.5 km S, killing 15 and injuring two people that had entered the 5-km exclusion zone without permission. On 4 February the number of displaced people reached 31,739 (9,915 families) in 42 evacuation centers, many from outside of the exclusion zone.

Geological Summary. Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

Sources: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM), Badan Nacional Penanggulangan Bencana (BNPB)