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TEMPO.CO, Bandung - Residents of Bogor City were widely reported to have heard rumbling and booming sounds or what sounded like explosions during a magnitude 4.1 earthquake that struck on Thursday night, April 10, 2025. Several residents described hearing loud booms on two separate occasions.
According to Daryono, the Head of the Earthquake and Tsunami Center at Indonesia's Meteorology, Climatology, and Geophysics Agency (BMKG), these noises were caused by high-frequency vibrations occurring close to the Earth's surface. This phenomenon also indicates that the earthquake's epicenter was at a very shallow depth.
"The Bogor earthquake being accompanied by rumbling and booming sounds is a normal occurrence. All very shallow earthquakes are accompanied by sounds such as explosions, booms, and rumbling," Daryono said in a written press release issued on Friday, April 11, 2025.
The epicenter of the Bogor earthquake on Thursday night, which occurred at 10:16 PM Western Indonesian Time (WIB), was recorded at a depth of five kilometers. Its geographical coordinates were 6.62 degrees South Latitude and 106.8 degrees East Longitude, placing it on land approximately 2 kilometers southeast of the Bogor City center.
An earthquake measuring a magnitude of 4.1 on the Richter Scale centered in Bogor City, West Java, April 10, 2025. BMKG
"The Bogor earthquake is strongly suspected to have been triggered by the Citarik Fault through a sinistral strike-slip mechanism," explained Daryono. Analysis of the BMKG earthquake map suggests that this fault line appears as a straight, right-sloping feature originating from the southern coastal tip of Sukabumi and extending towards or intersecting with areas near Bekasi.
Geological Agency Reports Stronger Tremors
However, Supartoyo, a leading earthquake investigator at the Geological Disaster Mitigation Research and Development Center (PVMBG) of the Geological Agency, expressed uncertainty regarding the Citarik Fault being the cause of the Bogor earthquake. "We are not yet certain that the fault extends that far," he commented on Friday, April 11, 2025.
The center of the 4.1-magnitude earthquake in Bogor City that occurred on Thursday night, 10 April 2025. According to BMKG, the earthquake's epicenter was on the Citarik Fault line, and therefore it was suspected that the earthquake was generated by the fault's activities. (BMKG)
Based on geological analysis, the area closest to the earthquake's epicenter, according to BMKG data, is Bogor City. Data from the Geological Agency indicates that Bogor and its surrounding areas primarily consist of hard to moderately firm soil types (classified as Class D), while the northern region is mostly composed of moderately firm to soft soil types (Class E).
According to the Geological Agency's data, the tremors around the epicenter were felt at an intensity level of IV-V on the Modified Mercalli Intensity (MMI) scale. An intensity of IV MMI is generally described as causing noticeable shaking indoors during the day, felt by many, and can cause doors and windows to creak.
Meanwhile, at an intensity of V MMI, the vibrations are felt by almost everyone. Tremors at this level can cause many people to wake up, pottery to break, and items to fall from shelves. "The distribution of residential areas affected by earthquake tremors is mostly located in Medium and High Earthquake Disaster-Prone Areas (KRB)," according to a statement from the Geological Agency.
Earlier information from BMKG reported that the earthquake was felt in Bogor Regency and City, as well as Depok City, at an intensity level of III-IV MMI. An intensity of III MMI is typically described as a tremor felt noticeably indoors, similar to the vibrations caused by a passing truck.
"Slight damage to some residential buildings in Bogor City" was reported by Daryono. According to BMKG monitoring, as of Friday morning, April 11, 2025, at 6:00 AM WIB, four aftershocks were recorded with magnitudes ranging from 1.6 to 1.9.
Series of Shallow Earthquakes in Bogor on April 10
The magnitude 4.1 earthquake on Thursday night occurred in Bogor following a magnitude 2.9 earthquake earlier that afternoon. The afternoon earthquake, which struck at 4:32 PM WIB, was felt in parts of the Bogor Regency at an intensity of II-III MMI. Based on BMKG analysis, this earlier event in Bogor was centered on land, approximately 28 kilometers southwest of the Bogor City center.
The map of the Bogor earthquake center that occurred on Thursday afternoon, April 10, 2025. BMKG
According to BMKG, the source of this earlier earthquake was also shallow, originating at a depth of eight kilometers. The cause was attributed to general active fault activity in the region. BMKG recorded one aftershock following this event.
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