TEMPO.CO, Jakarta - A series of earthquakes occurred in a number of areas in Indonesia after the earthquake in Cianjur, West Java. An earthquake occurred on Saturday, December 3 at 16.49 Western Indonesia Time (WIB) with a magnitude of 6.4 centered in Garut Regency with the epicenter at a depth of 118 Km, 52 Km southwest of Garut.

A day later, an earthquake hit Bangkalan on Sunday, December 4 at 22.02 WIB. The epicenter came from 6.42 south latitude and 112.60 east longitude at a distance of 77 kilometers northwest of Bangkalan.

Gunung Kidul Regency was also shaken by four earthquakes during the night. Followed by an earthquake on Tuesday, December 6 in Jember Regency, East Java, with a magnitude of 6.2 and other earthquakes. How do experts explain this recent series of earthquakes?

Earthquake expert and Gadjah Mada University (UGM) Geological Engineering Lecturer Gayatri Indah Marliyani – citing the university’s official website – believes that the earthquake that devastated Cianjur on November 21 was not a trigger for following earthquakes that occurred in other Indonesian regions.

According to her analysis, the only earthquakes related to the Cianjur earthquake were only a series of aftershocks concentrated around the epicenter area with decreasing frequency and magnitude.

The earthquake in Probolinggo, according to her, is related to the activity of the active Probolinggo fault which happened on land, while the Garut earthquake was related to the subduction process.

"The Garut earthquake occurred in the intraplate zone of the Indo-Australian plate which infiltrated under the island of Java. Meanwhile, the earthquake in East Java was in the accretionary prism zone in the eastern Java subduction zone," she said as cited from UGM's official website on Thursday, December 8.

Unrelated Natural Disasters

Judging from geographical areas along the subduction zone, such as along the west coast of Sumatra to Lombok, are in an active tectonic area, which is why she deems the consecutive quakes to be a normal phenomenon around this area.

The Indo-Australian, Eurasian, Pacific, and Philippine plates and several other plates move at a speed of about 4-7 cm per year which results in accumulated energy from the movement of the aforementioned plates, causing cracks and fault movements that are accompanied by earthquakes.

"There is no need to panic and worry too much about this natural phenomenon. Raising awareness of the surrounding environment can help us to prepare ourselves for disasters that may occur," she said.

TEMPO.CO | DEVI ERNIS

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