Sileri crater located in Dieng Volcano, with a geographic position in the Batur Subdistrict, Banjarnegara Regency, Central Java, has experienced phreatic eruptions in this crater. Among them on the date of July 2, 2017 a phreatic eruption occurred at 11:54:24 WIB, issued a mudflow material as high as 150 m, a distance of 50 meters from the crater to the south and north side. Then on April 1, 2018 at 13:42:55 WIB, there was a phreatic eruption in the Sileri Crater, which released a mudflow with a height of about 150 m. On April 8, 2018 at 11:21:03 WIB again a phreatic eruption with a height of about 50 meters and the material being sprayed about 20 meters from the crater to the east side.
Field Monitoring Result
The results of monitoring in the field show phreatic eruptions in the form of mud bursts with a height of about 50 m, with the distribution of mud material as far as about 20 m, to the east from the center of phreatic eruptions in the Sileri Crater. From the results of gas measurements around Crater Sileri no harmful gas was detected. CO2 gas is 0.04 vol% (below the normal threshold of 0.5 vol%), while H2S and SO2 gases are not detected.
Instrumental Monitoring
- Visual
Monitoring using a digital seismograph records the phreatic eruption earthquake at 11:21:03 WIB (Sileri Station) with a maximum amplitude of 9.5 mm, the duration of the earthquake is 16-18 seconds. The earthquake before the phreatic eruption was not recorded by any significant volcanic or tectonic earthquakes that preceded it. On April 7, seismographs only record 1 type of Local Tectonic earthquake.
- Temperature
Telemetry (TLR) temperature monitoring in Sileri Crater records data on April 8, 2018 from 00:02:56 to 15:03:14 WIB, increasing from 71.5˚C to 76.3˚C (sensor Ch.1); and from 71.8˚C to 81.1˚C (sensor Ch.2). The increase in the temperature of Crater Sileri water has been detected since April 3, 2018, which is from 48.8˚ C to 58.8˚ C on April 6 2018 which is measured manually. The increase in the temperature of the crater on April 6, 2018 has been coordinated with PT Waterboom DQIANO as a tourism manager for preparedness and alertness.
Follow-up
After monitoring the phreatic eruption in the Sileri Crater, Dieng volcano observers immediately conducted an inspection of the affected areas around the Crater of Sileri, and coordinated with relevant agencies: Banjarnegara BPBD, Batur KORAMIL, Batur POLSEK, Banjarnegara District Government, Volunteers, and PT Waterboom DQIANO.
Recommendation
- The citizen and tourists do not approach Sileri Crater at a distance of 200 meters from the edge of the crater.
- The citizen must stay calm and not being provoked by any issues related to the activities of the Dieng Volcano and to always follow the instructions of the Regional Disaster Management Agency (BPBD) of Central Java Province.
- The Provincial Governments of Central Java and BPBD of Banjarnegara Regency, Wonosobo BPBD, and Batang BPBD always coordinate with the Center for Volcanology and Geological Disaster Mitigation or through the Dieng Volcano Observation Post in Karangtengah Village, Batur sub-district, Banjarnegara regency, Phone 082330123236, about Dieng Volcano activities.
Source: Center for Volcanology and Geological Disaster Mitigation, Geological Agency, Ministry of Energy and Mineral Resources. Ir. Kasbani, M.Sc.
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