What caused the Johor quake and is S'pore safe from such tremors?

By Clara Lai and Seah Kwang Peng

A rare earthquake with a magnitude of 4.1 struck Johor on August 24, causing tremors in some parts of Negeri Sembilan and Melaka.  Residents reported feeling their homes shake. The incident sparked questions about the risk of earthquakes in Singapore and what causes such tremors.

What causes earthquakes?

Earthquakes occur when there is a sudden release of energy in the Earth's crust. This happens when accumulated strain, typically along faults or plate boundaries, is released, causing ground shaking. Seismic waves travel from the point of release, known as the focus, spreading outwards.

Most earthquakes take place at the boundaries of tectonic plates. These plates continually move, sliding past and colliding with one another. When the stress exceeds the strength of rocks, the energy is released as earthquakes.

What causes intraplate earthquakes?

While most earthquakes are interplate – occurring at pl

ate boundaries – intraplate earthquakes take place within a plate.

These are less common, as the stress within plates tends to be much lower. However, intraplate earthquakes can occur when there are old faults or weak zones inside plates. Local volcanism or human activities such as mining and reservoir-induced seismicity can also trigger them.

How frequent are such earthquakes in Malaysia?

Peninsular Malaysia is historically not prone to earthquakes. Most of Malaysia's earthquakes are located off the west coast of Sabah and near the boundary with Indonesia, which is part of the Pacific "Ring of Fire".

However, Peninsular Malaysia is not immune. A small number of intraplate earthquakes have occurred, including the 2015 quake in Ranau, Sabah.

How is Singapore affected by these earthquakes?

Singapore is situated on stable ground, away from tectonic plate boundaries, making it one of the world's least seismically active regions.

However, strong earthquakes in nearby regions, such as Sumatra, have caused tremors felt in high-rise buildings. These tremors usually cause no damage.

Is Singapore safe from such tremors?

Experts say the likelihood of a damaging earthquake occurring in Singapore is extremely low. The country is not located near major fault lines and stringent building codes ensure that structures can withstand minor tremors.

While tremors may be felt from distant earthquakes, they generally pose minimal risk to safety and property.