PUTRAJAYA: More seismic activity is expected to occur around Segamat, following several tremors since last Sunday, with the latest measuring 2.7 on the Richter scale, which was recorded at 7.29am today.

Universiti Teknologi Malaysia (UTM) earthquake engineering expert Professor Dr Azlan Adnan said that in addition to the ongoing tremors, there is also a possibility of larger quakes, exceeding 5 in magnitude on the Richter scale.

He explained that in earthquake science and engineering, there are three types of seismic events: "foreshocks" (preliminary tremors), "main shocks" (primary quakes), and "aftershocks."

"If the 4.1 quake is the 'main shock' (a common phenomenon), aftershocks will occur with lower magnitudes, less than 4.1. These aftershocks can continue for days, weeks, and even months, or up to two years, as seen in Bukit Tinggi following a 4.7 earthquake," he said.

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"If this 4.1 quake is a 'foreshock' or a warning of a larger quake, a bigger tremor exceeding 5 could occur," he added.

However, he said the issue at hand is that it is not yet clear whether the 4.1 tremor is the 'main shock' or a 'foreshock' until a larger quake occurs in the coming years.

Given this, he warned that the possibility of further quakes remains, and urged all parties to stay vigilant.

To address this, Azlan emphasised the need for ongoing monitoring and structural assessments, particularly since many buildings in the country have not been designed to withstand earthquakes.

Asked if human activities could contribute to the earthquakes around Segamat, including today's tremor, Azlan noted that small-scale tremors can generally be triggered by human activities such as quarry explosions, groundwater pumping, or changes in reservoir water levels.

However, he said that the current pattern in Segamat, starting with the 4.1 earthquake followed by five aftershocks, with magnitudes down to 2.7 at a shallow depth of 10 km, is more consistent with natural fault movements.

"Quarry explosions are usually very shallow, with fast waves that rarely produce aftershocks lasting for days," he explained.

"In short, while human activities may contribute to the tremors, the primary cause in Segamat appears to be the reactivation of a natural fault," he added. 

"However, I recommend that quarry data (timing and location of explosions) be reviewed alongside seismic activity to rule out the possibility of tremors being caused by quarry operations."

When asked if the presence of hot springs indicated the potential for a volcano, Azlan said it usually signals deep fractures and heat or water flow along faults.

He clarified that, so far in Peninsular Malaysia, this is not an indication of an active volcano like those in Sumatra or Japan.

"However, the presence of hydrothermal features suggests a weak zone in the crust where stress can accumulate or be released," he explained.

"Therefore, while people need to be cautious, it is not because of a volcano, but because an active fault could cause small to moderate tremors."

Azlan urged the public to be aware of safety procedures, avoid placing heavy structures on soft ground near cracks or hot springs, and report any new fractures to the authorities.