Merapi Eruption

Mount Merapi Status Increased from Level I (Normal) to Level II (Alert) May 21, 2018

1. Observation Result

Based on visual observations from Observation Post and CCTV, sunny weather occurs during the day, morning, and evening until the night is dominantly misty, accompanied by windy rain. Solfatara smoke is generally thick white, weak gas pressure with a maximum height of 25 m, observed from the Kaliurang Post. The weather at Pasar Bubrah is 12° C, humidity 92.3% RH, air pressure 74.26 kph, maximum wind speed 23.28 km/hr, and dominant wind direction from Northwest to Southeast.

Monitoring posts reported roar along with phreatic eruptions three times on May 21, 2018 each at 1:25 WIB, 19-minute duration of 700 m eruption column, at 09.38 WIB duration 6 minutes the height of the eruption column 1200 m, and at 5:50 WIB the duration of the 3-minute eruption column was not observed. Phreatic eruptions that occurred on May 21, 2018 were counted intensively. Previous phreatic eruption occurred on May 11, 2018 after about 4 years there was no phreatic eruption. This week, the earthquake of Mount Merapi was recorded 1 time volcanic earthquakes (VT), 12 times multiphase earthquakes (MP), 1 earthquake tremor, 12 earthquake collisions (RF), 3 earthquake eruptions, and 5 tectonic earthquakes (TT). The earthquake that occurred on May 20, 2018 at 21:30 WIB was classified as large and could be heard by citizen.

On May 21, 2018, the earthquake of Mount Merapi was recorded 1 times a volcanic earthquake (VT), 1 time earthquake tremor, 2 earthquake avalanches (RF), 3 earthquake eruptions, and 3 times tectonic earthquakes (TT).  The VT and tremor earthquake occurred after the eruption at 17:50 WIB. The Tremor earthquake has a frequency of about 0.2 Hz with an average amplitude of 5-10 mm.

The temperature of the center of the crater is around 85° C, increasing from normal conditions (<50° C).

• Conclusion

Depend with an increase in phreatic eruption activity and followed by VT earthquakes and tremor earthquakes, it was concluded that the volcanic activity of Mt. Merapi had increased.

With the increase in these activities, starting from 21 May 2018 at 23.00 WIB, the activity status of Mt. Merapi is raised from the NORMAL level to BEWARE.

• Recommendation

With the increase in the activity status of Mt. Merapi from NORMAL to be BEWARE to stakeholders in Mt. Merapi disaster management, it is recommended as follows:

• The climbing and hiking activity of Mt. Merapi is temporarily not recommended except for the purposes of investigation and research related to disaster mitigation efforts.
• Radius 3 km from the summit to be emptied of citizen activities.
• People who live in KRB III ask to increase awareness of the activities of Mt. Merapi.
• If there is a significant change in Mt. Merapi activity, the activity status of Mt. Merapi will be immediately reviewed.
• The citizen should not be provoked by issues regarding the eruption of Mount Merapi, whose sources are unclear and keep following the instructions of the local government officials or ask directly to the nearest Mt. Merapi Observation Post via radio communication at the frequency of 165,075 MHz, or through the website www.merapi.bgl.esdm.go.id,   BPPTKG social media, or the BPPTKG office, Jalan Cendana No. 15 Yogyakarta, call (0274) 514180-514192.
• The regional government is recommended to socialize the current condition of Mount Merapi to the public.

Phreatic Eruptions of Merapi Volcano May 21, 2018

1. Observation Result
   1. The seismicity of the May 19, 2018 was detected by multiphase (MP) earthquakes 2 times, 4 fall earthquakes, and 1 tectonic earthquake.
   2. On May 20, 4 times avalanches earthquake and a tectonic earthquake were detected 1 time. The earthquake which occurred at 21:29 WIB. was classified as moderate and reportedly heard by a resident in Srunen.
   3. On May 21 from 00.00 to 12.00, 2 times eruption earthquake was detected, first at 1:25 WIB and the next at 9.38 WIB, multiphase earthquake (MP) 3 times, 3 times avalanches earthquake, and Tectonic earthquake 2 times.
   4. There is no increase in temperature of the crater prior to phreatic eruption. An increase in temperature reaching 275 (maximum temperature of the device) was observed during the eruption.
   5. Volcanic Deformation which is instrumentally monitored using Tiltmeter, EDM and GPS does not show a significant change.
   6. Phreatic eruption of Mount Merapi occurred on May 21 at 1:25 WIB for 19 minutes. The height of the eruption column reaches 700 m above the peak. Ash rains are reported to spread to 15 km to the West.
   7. Phreatic eruption of Merapi Volcano occurred again at 09.38 WIB for 6 minutes. The height of the eruption column reaches 1200 m above the peak. Ash rains are reported to spread to 15 km to the West.
   8. After the eruption, the earthquake recorded did not experience a significant increase and the temperature of the crater decreased.
2. Conclusion
   1. The eruption that occurred today is an eruption triggered by the accumulation of volcanic gas.
   2. The status of Mt. Merapi activities is stated at the NORMAL level.
3. Recommendation
   1. Now, Merapi’s activity has subsided, people are encouraged to stay calm.
   2. Looking with the occurrence of ash rains in several places, the community and the local government conducted the mitigation of the danger of volcanic ash.
   3. The climbing and hiking activity of Mt. Merapi is recommended to only at Pasar Bubrah, except for the purposes of investigation and research related to disaster mitigation efforts. The peak morphological condition of Mount Merapi is currently prone to landslides, so it is very dangerous for the climbers safetyness.
   4. If there is a significant change in Mt. Merapi activity, the activity level of Mt. Merapi will be reviewed soon.

Phreatic Eruptions of Merapi Volcano May 11, 2018

1. Observation Result
   1. Seismicity from May 9, 2018 detected 2 times volcanic earthquakes (VT) and 8 times earthquake avalanches. On May 10, a volcanic earthquake 4 times was detected and 3 times avalanches earthquakes. On May 11, from 00.00 to 08.00 WIB, avalanche earthquake and a multi-phase earthquake were detected once.
   2. The results of monitoring the temperature of the crater, about 2 hours before the eruption, increased the crater rate in area 3 (inside the crater) increasing from 38.2 degrees Celsius at 01:00 to 90.6 degrees Celsius at 08:30 WIB.
   3. The deformation of Mount Merapi which was monitored instrumentally using EDM and GPS did not show a significant change.
   4. Based on visual observations, the Merapi Volcano eruption occurred on May 11, 2018 at 7:40 WIB beginning with a small roar, felt a vibration around the Observation Post of Mount Merapi Babadan with a duration of 10 minutes. The height of the eruption column reaches 5.5 km above the peak. There was a thin rain of ash and sand around Mount Merapi Kaliurang Observation Post. The eruption occurs once and is not followed by a subsequent eruption.
   5. After the eruption, the recorded earthquake did not change and the temperature of the crater decreased.
2. Conclusion
   1. It was concluded that the eruption that occurred at this time was a minor eruption triggered by volcanic gas accumulation and probably would not be followed by further eruptions.
   2. The status of Mt. Merapi activities is stated at the “NORMAL” level.
3. Recommendation
   1. Now, Merapi’s activity has subsided, people are encouraged to stay calm.
   2. The climbing and hiking activity of Mt. Merapi is recommended to only at Pasar Bubrah, except for the purposes of investigation and research related to disaster mitigation efforts. The peak morphological condition of Mount Merapi is currently prone to landslides, so it is very dangerous for the climbers safetyness.
   3. If there is a significant change in Mt. Merapi activity, the activity level of Mt. Merapi will be reviewed soon.

Source: KESDM, Geology Agency, PVMBG Geological Disaster Research and Development Center.