5 Unrelated Earthquakes In One Day

Illustration (Pixabay)

JAKARTA - From morning to noon, Tuesday, July 7, Indonesia was shaken by tectonic earthquakes 5 times. Even so, the Meteorology, Climatology and Geophysics Agency (BMKG) stated that the five earthquakes were not contagious and interconnected natural disasters.

First, the earthquake occurred in the morning at 03.31 WIB with a scale of 4 magnitudes in the Donggala area, Central Sulawesi. The epicenter of the earthquake is on land with a distance of 7 kilometers east of Toaya, Donggala Regency at a depth of 4 kilometers.

Then, at 05:54 WIB in the Java Sea region with a parameter of 6.1 magnitude. To be precise, the second earthquake occurred at sea at a distance of 85 kilometers from the north of Mlonggo, Jepara, Central Java at a depth of 539 kilometers.

"This is a type of earthquake due to deformation or enlargement of the subducted plate under the Java Sea," said BMKG Head of Earthquake and Tsunami Center Rahmat Triyono in his statement, Tuesday, July 7.

This second earthquake was felt in Karangkates, Nganjuk, Yogyakarta, Purworejo, Kuta, Mataram, Denpasar, Malang, Lumajang, Tulungagung, Blitar, Ponorogo, Pacitan, Surabaya, Wonogiri, Kebumen, Banjarnegara, Pangandaran, Karangasem, West Lombok, Garut, Boyolali areas. , Krui, Sekincau, Semaka, Pekalongan, Banyumas, Wonosobo, Magelang, Purbalingga and Gianyar.

Another earthquake occurred at 11.44 WIB in the Lebak area, Banten with a parameter of 5.1 magnitude. This third earthquake occurred on land at a distance of 18 kilometers from the southwest of Rangkasbitung at a depth of 87 kilometers. This third earthquake was felt as far as Jakarta.

"Earthquake shocks are very much felt in Jakarta because of the phenomenon of the site effect, where the effect of thick soft soil in the city of Jakarta triggers a resonance of earthquake waves, so that the earthquake shocks are amplified and the shocks are amplified," said Rahmat.

Not long after, the fourth earthquake occurred around the Pangandaran area, West Java at 12.17 WIB. The earthquake measuring 5 magnitude is centered in the sea with a depth of 10 kilometers.

More specifically, the epicenter was located 234 kilometers southwest of Pangandaran Regency, 247 kilometers from the southwest of Tasikmalya Regency, 254 kilometers from the southwest of Garut Regency, 280 kilometers from the southwest of Bandung City, and 364 kilometers from the southeast of Jakarta. .

Following that, the fifth earthquake occurred at 13:16 WIB with a magnitude of 5.2 in the Indian Ocean region of the West Coast of Sumatra. To be precise, the fifth earthquake occurred on land at a distance of 241 kilometers from the southeast of Enggano, Bengkulu at a depth of 10 kilometers.

"This is a type of shallow earthquake due to the subduction of the Indo-Australian plate that is submerged under the Eurasian plate. This earthquake shock was felt in Limau Tanggamus District," said Rahmat.

Not related

Rahmat explained, the earthquakes that occurred in a row today were not related to each other. Rahmat said, what happened in several earthquake areas was a manifestation of the release of stress fields at the respective earthquake sources.

Each earthquake source experiences its own accumulation of stress fields, reaches its own maximum stress, and then experiences energy releases as an earthquake itself. This is a logical consequence of areas with very active and complex earthquake sources.

"We do have many earthquake sources. So, if an earthquake occurs in a place that is relatively close to its location and occurs in a relatively close time, then it is just a coincidence," said Rahmat.

There is an assumption that the third and fourth earthquakes that occurred in South Banten and South Garut originated from the same earthquake source. This is because the two earthquakes occurred in close proximity of time and location. In fact, according to him, the two earthquakes originated from different earthquake sources.

"The southern Banten earthquake occurred due to rock deformation on the Indo-Australian Plate slab in the Benioff Zone at a depth of 87 kilometers, while the South Garut and South Sunda Strait Earthquakes were triggered by rock deformation on the Indo-Australian Plate slab in the Megathrust Zone," he said.