Mount Anak Krakatau: What's Next After The Eruption?

Image of the eruption of Anak Krakatau (PVMBG)

JAKARTA - The Meteorology, Climatology and Geophysics Agency or BMKG conducted sea level and seismic monitoring related to the eruption of Mount Anak Krakatau on Friday to Saturday, April 11, morning. As a result, no sea level anomalies were found.

BMKG Head of Earthquake and Tsunami Mitigation Division, Daryono, said sea level monitoring uses two types of tools that are scattered in several locations. Tide Gaude on Kota Agung Beach, Panjang Harbor, Binuangen and Jambu Marina. Also Radar Wera which is located in Kahai, Lampung and Tanjung Lesung, Banten.

"The tide gaude activity closest to Mount Anak Krakatau is also absent. Including in Bakauheni, there are no tectonal earthquakes. So from the tide gaude records, radar wera, tsunami radar, and automatic water level there is no (potential) tsunami," he said. contacted VOI, in Jakarta, Saturday, April 11.

Meanwhile, the results of seismic monitoring carried out right at the time of the eruption, namely at 21.58 WIB and 22.35 WIB indicated that the BMKG sensor did not record any seismic activity.

"So that the eruption of Mount Anak Krakatau this time, based on BMKG sensor records, is weaker than the eruption that occurred on December 22, 2018," he said.

The BMKG also found something else from the results of the seismic monitoring, namely the earthquake in the Sunda Strait. The earthquake was recorded at 22.59 to 23.00 WIB several seismic sensors, both existing and new sensors installed in 2019.

BMKG analysis results related to the earthquake showed a tectonic earthquake occurred in the Sunda Strait at 22.59 WIB with a magnitude of 2.4. The center of the earthquake was at coordinates 6.66 latitude and 105.14 east longitude to be precise in the sea at a distance of 70 km south-west of Mount Anak Krakatau at a depth of 13 km.

Daryono appealed to the public not to panic excessively. This is because BMKG has provided information and developments regarding the condition of Mount Anak Krakatau (GAK).

"So that people who are worried are not afraid, because we have informed that there is no potential for a tsunami," he said.

Possible future

Daryono said, as an active volcano, GAK will show active volcanic symptoms. The small eruptions that are currently happening, he said, are something that is common.

"Like yesterday there were bubbles of seawater coming out of the seabed. That is something that is normal in an active volcano," he said.

Even so, Daryono said, the worse protection from GAK activities would not cause a tsunami. This is because some of the bodies of this young volcano have landslides and caused a tsunami at the end of 2018.

"To cause a tsunami, the body of the mountain must be large, and it must fall into the sea. Now the body is already small, there are already landslides on December 22, 2018. So there is a small potential for landslides that are large in scale. The potential (tsunami) is relatively small," he said.

Earthquakes don't always erupt

LIPI Associate Researcher in Applied Geophysics, Nugroho D. Hananto said, there are two types of earthquakes, namely tectonic and volcanic. The two of them are something different. Tectonic earthquakes arise due to plate movements that cause faults. As happened in Palu.

Then, continued Nugroho, the volcanic earthquake was due to magma activity in the body of the volcano. The characteristics of the earthquake differ from tectonics, so it can indicate the maturity of the magma beneath a volcano whether or not to erupt.

"But sometimes if we look at the volcanic earthquake, we estimate that it will erupt, but because there is an acid dynamic in the body of the volcano, it does not erupt. Indeed, most of the time there is an earthquake (volcanic) activity that is higher," he said.

Nugroho explained, even though the volcanic earthquake was intense, it would not necessarily cause the volcano to erupt and it might not have erupted.