Johor earthquakes caused by tectonic energy released without warning due to crustal movement, not volcanic activity

The two mild earthquakes that struck Johor, Malaysia on Sunday, Aug. 24 was due to tectonic energy being released without warning as a result of continental crustal movement.

According to a statement from the Malaysian Meteorological Department (MetMalaysia), both earthquakes had epicentres near the Mersing Fault Zone, a major fault belt in the peninsula, which trends from west-northwest to east-southeast.

No loss of life or injuries were reported.

Johor Mineral and Geoscience Department (JMG) director Noorazhar Ngatimin told Bernama: “This event points to the reactivation of an ancient fault, releasing stored tectonic energy within the continental crust."

"The quake’s depth confirms it originated from crustal movement, not volcanic activity or deep-sea subduction," he added.

Quakes occurred before in Malaysia

He also noted that fault reactivation is not new in Peninsular Malaysia.

Records show Johor experienced two earthquakes in 1922, a magnitude 5.4 quake on Jan. 31, as well as a magnitude 5.0 quake on Feb. 7, causing minor damage in Muar.

Previous tremors occurred in Bukit Tinggi, Pahang between 2007 and 2010, as well as in other areas in Malaysia, such as Kenyir, Terengganu in 1984.

“Such events are rare because Peninsular Malaysia sits on the Sunda Plate, a relatively stable tectonic zone,” he said.

He also noted that Johor felt minor tremors in 2021 and 2023, though those quakes originated offshore near Sumatra.

According to CNA, there was an earthquake in December 1948 near southern Singapore and the tremors were felt in Geylang, Bukit Timah, Sentosa island and reportedly damaged a house in Chinatown.

Noorazhar advised that proactive measures are still needed to safeguard public safety and economic stability, even though the risk of a quake is lower compared to Sumatra.

Background

A pair of earthquakes struck northern Johor on Aug. 24.

Tremors were felt in several Malaysian states including Negeri Sembilan, Melaka and Pahang.

Falling debris from the ceiling and cracks on the wall resulted.

The initial 4.1-magnitude quake occurred at about 6:15am, 5km west of the town of Segamat at a depth of 10km.

The second milder 2.8-magnitude quake occurred at 9am, 28km northwest of Kluang town.

Top photos via Research Gate & MetMalaysia