There are 33 Aftershocks BMKG Calls the Banten Earthquake an Intraslab Earthquake

The Banten earthquake caused quite a lot of damage. (photo: doc. Antara)

JAKARTA - From Friday afternoon to Saturday, January 15 at 12.00 western Indonesia time, the Meteorology, Climatology, and Geophysics Agency (BMKG) has recorded 33 aftershocks after the Banten earthquake with a magnitude of 6.7 last Friday.

"The aftershocks that occurred had the largest magnitude of 5.7 and the smallest magnitude of 2.5," said the BMKG Earthquake and Tsunami Mitigation Coordinator, Daryono through a short message received in Jakarta, Antara, Saturday, January 15.

The earthquake, which was previously recorded with a magnitude of 6.7, was centered at sea at a distance of 132 km southwest of Pandeglang City, Banten, with a hypocenter depth of 40 km which had a thrust fault source mechanism due to a strong pressure process.

This earthquake is destructive or destructive. Based on BPBD data in Pandeglang Regency, the earthquake-affected areas included 113 Kelurahan from 17 Subdistricts, causing more than 700 houses and more than 30 public facilities to be damaged.

The earthquake did not have the potential for a tsunami because its magnitude was still below the average threshold for a tsunami-generating earthquake of 7.0 plus a hypocenter depth of 40 km.

Sea level monitoring data does not show any record of changes in sea level after the earthquake, this is evidence that the earthquake that occurred did not trigger a tsunami.

The type of earthquake is a shallow earthquake due to deformation or rock fractures in the Indo-Australian Plate which is subducted/subducted under the Sunda-Banten Strait.

Experts call this type of earthquake an intraslab earthquake. The hallmark of an intraslab earthquake is that it is able to radiate ground motion that is larger and stronger than an earthquake of its class from other sources. So it is natural that this earthquake has a very broad spectrum of shocks felt as far as South Sumatra to West Java.

Earthquake shocks were also felt very strongly in Jakarta due to the local site effect of soft and thick layers of soil in the Jakarta area which triggered the resonance of earthquake waves until finally the ground shaking experienced amplification or enlargement in addition to the long period vibration phenomenon (long period vibration) due to a strong earthquake whose source is relatively far away.

According to Daryono, the earthquake on Friday afternoon was similar to the 6.1 magnitude South East Java earthquake on April 10, 2021, which was also destructive. Both intraslab earthquakes are earthquakes with sources within the Indo-Australian Plate.