Recent Updates on Mount Agung Volcanic Activity (5 October 2017 17:00 Central Indonesia Time/CIT UTC+8) 5 October 2017 18:58 WIB, Ir. Kasbani, M.Sc.
A. Observational Data
2. Visual Observation
- The rate of volcanic earthquakes in the last 12 days has not accelerated but continues to fluctuate at high levels. In average, there are still 1-3 earthquakes per minute with the total number reaching greater than 600 per day.
- Shallow volcanic earthquakes from September 24 to October 5, 2017 have increased in number (generally more than 200 earthquakes per day) when compared with the previous period (generally less than 200 earthquakes per day). This may indicate that magmatic activity at shallow depths is still high.
- The largest earthquake to be recorded during this crisis is a M4.3 (27 September 2017 13:12 Central Indonesia Time/CIT UTC+8). It was felt in the local area with an intensity of MMI III-IV (Modified Mercalli Intensity). Most of the largest recorded earthquakes have a magnitude between M2.0-M3.0. The number of felt earthquakes at the Mt. Agung Volcano Observatory in Rendang village (AVO Rendang) (around 12.5 km to the South-Southwest of the volcano) reached a maximum on September 27, 2017 with 14 events. After that, the number of earthquakes felt at the AVO Rendang has decreased.
- Earthquakes are located under Mt. Agung with a range in depths up to 20km below the summit.
- Real Time Seismic Amplitude (RSAM) in the last 12 days has not increased but remains at a high level.
- Earthquake activity is still dominated by high frequency events. This indicates that seismic activity at the volcano still represents the brittle failure of rock inside the volcano in response to magmatic intrusion.
- Changes in seismic velocity indicate that pressurization under the volcano continues as the intruded volume of magma into the system increases and as magma moves towards the surface.
3. Satellite Remote Sensing
- Gas emissions from the crater, as observed from AVO Rendang (South sector) and AVO Batulompeh (North sector), appear as thin to thick white clouds that reach a height of 50-200 m above the crater rim.
- Satellites have detected steam emissions and thermal areas within the summit crater. During the crisis period, these areas have expanded along the north-east edge and including an area of emissions in the center of the crater.
- Water expulsion in the crater near the solfatara field has been observed by satellite. Water expulsion is thought to reflect a disturbance to the hydrologic system in response to intruded magma at depth.
- Tiltmeter observations showed a sudden deflation on October 1, 2017, but following days until today showed continued inflation.
- Differential optical absorption spectroscopy (DOAS) gas measurements made at a distance of 12 km from the summit did not detect any SO2. This lack of detection can not necessarily be interpreted as a lack of SO2 or magmatic activity. SO2 concentrations may be below the detection threshold of the instruments, or emitted SO2 content may be reduced due to scrubbing (removal of SO2 gas as a result of interaction with water).
- White smoke coming from the crater is potentially accompanied by the release of magmatic gases (CO2, SO2, etc.). If the concentration is high, these gases can smell, sting, and endanger the safety of those who inhale it. However, the current hazard from gas exposure is likely to be limited to the area around the crater. These gases will be easily blown and scattered by the wind so that the concentration will decrease significantly distance.
- MultiGas measurements at Mt. Batur do not indicate the supply of new magma under Batur. As of today, all indications suggest that all recent activity is related to Mt. Agung.
- The evaluation of observational data indicates that volcanic activity at Mt. Agung remains at a high level. It is still more likely than not that an eruption will result from current activity. Probabilities of eruption, however, can change with time and are dependent on changes in observational data.
- If an eruption were to occur, it is likely that the first eruption would be small. Larger eruptions could follow initial, smaller eruptions. The size of impending eruptions, however, can not be forecasted precisely.
- The exact date and time of a possible eruption can not be predicted. CVGHM will, however, issue warnings as early as possible if activity at Mt. Agung changes or if the probability of eruption increases.
- Residents and tourists who remain outside of the hazard zone may continue their normal activities. The current hazard zone extends as a 9km radius from the summit and up to 12 km from summit towards the N-NE and SE-S-SW sectors.
- Tourists activities are still considered safe in Bali. Residents and tourists, however, may not enter the Hazard Zones. CVGHM continues to work with BNPB (National Agency for Disaster Management) as well as local governments to improve eruption early warning systems.
- Tourists and residents in Bali are encouraged to comply with recommendations set by the Government of Indonesia. Official information issued by CVGHM on the activity at Mt. Agung can be accessed via Magma Indonesia, which is available on the web(magma.vsi.esdm.go.id) or the GooglePlay store.
C. Preparedness Coordination
From 29 September - 5 Oktober 2017, CVGHM, Badan Geologi (Geologic Agency), ESDM (Ministry of Energy and Mineral Resources) has been coordinating activities in an effort to increase preparedness for the potential threat of eruption hazards, including:
- Coordination meetings with the Governor of Bali and the head of BNPB regarding the return of evacuees who live within the exclusion zone set with Level IV (Awas).
- Disseminating information regarding recent activity at Mt. Agung as discussed during the coordination meetings to the Posko Tanah Ampo.
- Coordination meetings with BMKG (Meteorology Climate and Geophysical Agency) as it relates to the need for meteorological data to model the effects of eruptive products.
- Socialization activities for local communities who rely on hotel and tourist industries in Kab. Badung.
- Coordination meetings to make contingency plans for lahar and ash fall hazards.
- Coordination meetings with BNPB to identify evacuation routes for local stakeholders.
- Disseminate information of recent activity to domestic and international print and electronic media outlets.
- Aerial and terrestrial field surveys to verify areas of potential hazards.
- Explain the volcanic hazard map to village heads for those villages that are located in the hazard zones.
Ministry of Energy and Mineral Resources