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Report on Semeru (Indonesia) — June 2002

Bulletin of the Global Volcanism Network, vol. 27, no. 6 (June 2002)
Managing Editor: Richard Wunderman.

Semeru (Indonesia) Seismicity increases beginning in March 2002; Alert Level increased to 2

Please cite this report as:

Global Volcanism Program, 2002. Report on Semeru (Indonesia) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 27:6. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200206-263300.

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Semeru

Indonesia

8.108°S, 112.922°E; summit elev. 3657 m

All times are local (unless otherwise noted)


Since mid-July 2001, Semeru was at Alert Level 1 (on a scale of 1-4). On 8 March 2002 two pyroclastic flows traveled 2.5 km downslope to the Besuk Kembar river. The same day, tectonic and volcanic earthquakes increased, prompting the Volcanological Survey of Indonesia (VSI) to raise the Alert Level to 2. Tectonic and volcanic earthquakes continued, along with explosions, avalanches, pyroclastic flows, and tremor (table 7). Plumes, sometimes containing ash, were visible reaching up to 500 m above the summit (table 8).

Table 7. Seismicity registered at Semeru during 3 March-16 June 2002. "--" indicates that information was not reported. Courtesy VSI.

Date Deep volcanic Shallow volcanic Explosion Avalanche Local tectonic Pyroclastic flow Tremor Far tremor
03 Mar-10 Mar 2002 8 1 479 22 2 2 -- --
11 Mar-17 Mar 2002 1 2 444 21 -- -- 3 --
18 Mar-24 Mar 2002 2 -- 514 10 1 -- -- --
25 Mar-31 Mar 2002 9 6 302 171 1 -- 2 --
01 Apr-07 Apr 2002 26 2 415 278 -- -- -- --
08 Apr-14 Apr 2002 9 -- 509 141 3 -- 1 --
15 Apr-21 Apr 2002 16 4 791 194 -- -- -- --
22 Apr-28 Apr 2002 6 0 585 64 3 0 5 14
29 Apr-05 May 2002 0 0 664 52 0 0 3 14
06 May-12 May 2002 5 0 783 62 0 0 0 15
13 May-19 May 2002 1 0 575 146 0 0 0 13
20 May-26 May 2002 -- -- -- -- -- -- -- --
27 May-02 Jun 2002 2 1 556 90 1 -- 2 --
03 Jun-09 Jun 2002 2 -- 556 45 -- -- 1 --
10 Jun-16 Jun 2002 2 -- 637 31 -- -- -- --

Table 8. Plumes observed at Semeru during 8 March-16 June 2002. Courtesy VSI.

Date Plume Type Plume height (above the summit)
08 Mar 2002 White-gray 400 m
12, 14, and 17 Mar 2002 White-gray 300-400 m
19-23 Mar 2002 White-gray ~300-500 m
25-31 Mar 2002 White-gray 300-500 m
15-21 Apr 2002 White-gray, medium pressure 400 m
22 Apr-26 May 2002 White-gray, medium pressure 400 m
10-16 Jun 2002 White-gray ash 200-400 m

On 31 March two tremor earthquakes occurred with amplitudes of ~3-17 mm. During mid-April, a tremor earthquake occurred with an amplitude of 0.2 mm. Lava avalanches continued to travel up to 750 m down to Besuk Kembar. Seismic signals thought to indicate local floods registered 15-21 April. Incandescence was observed up to 25 m above the crater rim during 1820-2025 on 18 April. During that time, seismicity was dominated by low-frequency earthquakes, with amplitudes of 2-3 mm. During 27 May-2 June ash explosions produced white-gray plumes that reached ~200-400 m above the summit, while lava avalanches traveled ~100 m away. Semeru remained at Alert Level 2 through at least 16 June 2002.

Geologic Background. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Information Contacts: Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).