The Reason Strong Tremor Felt In Jakarta Even Though The Earthquake Happens In Banten

Employees scattered out of the building on MH Thamrin street, Jakarta, an earthquake with a magnitude of 6.7 in Banten was felt as far as Jakarta, Friday, January 14. ANTARA PHOTOS/Dhemas Reviyanto/aww.

JAKARTA - The Meteorology, Climatology and Geophysics Agency (BMKG) explained the reason DKI Jakarta also felt the strong tremor, even though the epicenter of the earthquake was far from the area.

Head of the Center for Technical Seismology, Potential Geophysics, and BMKG Time Signs, Rahmat Triyono, in a written statement, said that the magnitude 6.6 earthquake in Banten on January 14, 2022 was felt as far away as DKI Jakarta.

In fact, the epicenter of the earthquake was located at coordinates 7.21° South Latitude; 105.05° east longitude, or to be precise, located at sea at a distance of 132 km southwest of Pandeglang City, Pandeglang Regency, Banten at a depth of 40 km.

"The earthquake that was felt in Jakarta on January 14, 2022, again reminds the public, especially the Jakarta area as the center of government and the many high-rise buildings, where when the earthquake on January 14, 2022, was felt quite strong," said Rahmat in an official statement received in Jakarta, as reported by Antara, Tuesday, January 25.

He said the earthquake was felt in Jakarta, not just this time. The 7 August 2019 earthquake and the 23 January 2018 Banten earthquake were a series of earthquakes that were reported to be felt as far as Jakarta.

BMKG at the time of an earthquake provides information on the level of shock which is a representation of the acceleration value of ground vibrations obtained from equipment called an accelerometer.

The equipment has units of information value in units of g (gravity), m/s2, and cm/s2 which are also commonly referred to in units of gal.

Through observations of the BMKG accelerometer equipment network, one of the sensor points at the Jakarta City Hall showed a vibration value of 2.5 gals.

Then in an area further north at the Kemayoran location, one of the buildings with accelerometers installed on the ground floor and 12th floor shows a value of 6.1 gals on the ground floor and 22.6 gals on the 12th floor.

From a sample of one of the monitoring responses to the building, it shows that the Kemayoran area produces amplification of 3.6 times from the ground floor to the 12th floor for the type of vertical shock.

Other information explains that the further north you go, the higher the maximum ground acceleration (PGA) on the ground floor. This fact shows an appropriate correlation with the sedimentary soil conditions in the Jakarta area.

If viewed from the local site effect conditions in the Jakarta area, the further north the road is, the deeper the estimation of the engineering bedrock depth in the Jakarta area will be.

The earthquake which has been felt strongly in Jakarta several times, if you look at the comparison of the recording recorded by the accelerometer to the threat level design in the 2019 SNI Indonesia Earthquake Hazard Map in Jakarta, the results show that it is still far from the calculation of the design scenario for the vibration threat level which is calculated for the worst scenario for the region of Jakarta.

Where the target value is 375 gals from the results of the Earthquake Map application plot for the Central Jakarta City Hall area.

The threat value is correlated with the background of the geological conditions of Jakarta, which is getting to the north the thicker the form of sediment (sediment), which is the result of the formation of coastal deposits, swamps, and rivers.

"Based on the facts of the January 14, 2022 earthquake south of Banten, a review of the need to update the condition of information on the resilience of existing buildings in the DKI area by conducting an assessment is something that must be done," said Rahmat.

The Regional Government with the Governor's Regulation that already has it can implement it through the BPBD and the Cipta Karya to carry out evacuation methods and guidelines to measure the condition of existing buildings," said Rahmat.

In addition, it is necessary to formulate the provision of regional regulations on the implementation of development planning so that SLF (Other Functional Certificates) can be granted for buildings that have been assessed, as well as the need for a policy of attention to buildings under 8 floors whose construction is not through the Building and Building Expert Team (TABG) is in the process of issuing a Building Permit (IMB).