BMKG’S CLARIFICATION REGARDING THE SERIES OF EARTHQUAKES IN MAMBERAMO RAYA

Clarification provided by BMKG in regard to the series of earthquakes in Mamberamo Raya

A series of earthquakes rocked Central Mamberamo, Mamberamo Raya Regency, Papua, Saturday (10/9/2022) morning. As quoted from https://papua.inews.id/, there were four series of earthquakes with a Magnitude of 5.9, M 6.9, M 5.5 and M 6.2 from 06.31 WIT to 07.05 WIT.

Acting Head of the Earthquake and Tsunami Center of the Meteorology, Climatology and Geophysics Agency (BMKG), Daryono, said the results of the BMKG analysis showed that the earthquake had an updated parameter for the first earthquake of a magnitude of M 6.1, the second earthquake of a M 5.9, the third earthquake of a M 5.5 and the fourth earthquake of a M 6.2.

The epicenter of the first earthquake was located at the coordinates of 2.21 LS, 138.25 BT or precisely located on land at a distance of 8 km northeast of Central Mamberamo, Mamberamo Raya, Papua at a depth of 19 km. Daryono said, taking into account the location of the epicenter and the depth of the hypocenter, the four earthquakes that occurred were shallow earthquakes due to the Anjak Mamberamo fault activity.

“The results of the analysis of the source mechanism show that the four earthquakes have an upward movement mechanism,” he said. The earthquake had an impact and was felt in the Sarmi area with an intensity scale of IV MMI (if during the day it was felt by many people in the house), the Mamberamo area with an intensity scale of III MMI (real vibration was felt in the house. The vibration felt was like a truck was passing by) and Jayapura area with an intensity scale of II MMI (vibration felt by several people was swaying of light objects).

So far, there have been no reports of damage as a result of the earthquake. The model results show that the earthquake did not have the potential for a tsunami. “We urge the public to remain calm and not be influenced by issues that cannot be justified. We also urge the public to stay away from buildings that were cracked or damaged by the earthquake,” he said.

Quoting https://vsi.esdm.go.id/, the Mamberamo Raya Regency area is composed of plain morphology, plains to curvy plains, and rolling hills to steep hills. Based on the Geological Map of the Sarmi and Bufareh Sheets published by the Geological Agency in 1995, the area of Mamberamo Raya Regency is generally composed of Quaternary deposits in the form of river deposits, swamp deposits, and coastal deposits, as well as Tertiary-aged rocks in the form of sedimentary rocks (limestone, sandstone, claystone, flakes and conglomerates).

Some of the Tertiary-aged rocks have undergone weathering. Quaternary deposits and rocks of Tertiary age that have undergone weathering are generally soft, loose, unconsolidated and strengthen the effects of shocks, making them prone to earthquakes.

Based on data on the location of the earthquake center and depth, the occurrence of this earthquake is associated with active fault activity with an upward fault mechanism. According to data from the Geological Agency, this rising fault is trending relatively northwest – southeast.

Until this report was made, no information has been obtained about casualties and damage to buildings due to the earthquake. According to kompas.com information, people around the location of the earthquake’s epicenter had panicked due to the series of tremors.

According to information from the BMKG, the earthquake shocks in the Mamberamo Raya and Sarmi districts were felt on the MMI (Modified Mercalli Intensity) IV intensity scale.

According to data from the Geological Agency, the distribution of residential areas affected by earthquake shocks is located in the Disaster-Prone Areas (KRB) for medium to high earthquakes.

This earthquake did not cause a tsunami because the epicenter of the earthquake was located on land. The government urges the public to remain calm and follow directions and information from local BPBD officers, but remain alert to aftershocks.

In addition, do not be provoked by irresponsible issues regarding earthquakes and tsunamis. Buildings in Mamberamo Raya Regency must be constructed using earthquake-resistant building construction.

In addition, it must be equipped with evacuation routes and areas. The area of Mamberamo Raya Regency is classified as prone to earthquake disasters, which originate mainly from active faults on land.

Therefore, it is recommended that earthquake disaster mitigation activities be increased through structural mitigation and non-structural mitigation. This earthquake is estimated to have the potential to cause collateral hazards in small dimensions (such as ground cracks, ground movement and liquefaction).