A weak earthquake that struck Temenggor early Friday morning may have been linked to the huge volume of water held in its man-made lake - a phenomenon known as a reservoir-induced earthquake.
Perak Mineral and Geoscience Department (JMG) director Nizarulikram Abdul Rahim had raised this possibility. It is supported by a 2021 scientific study that identified Temenggor as one of two areas in Peninsular Malaysia associated with possible reservoir-induced earthquakes.
Nizarulikram told Malaysiakini that he had checked the location with the Perak division of the Meteorological Department, and confirmed that the epicentre of the Friday tremor was within the Temenggor Lake area.
Temenggor Lake is the second-biggest man-made lake in the peninsula, and was the result of creating the Temenggor Dam, which generates electricity.
When contacted, Tenaga Nasional Berhad (TNB), which manages the dam, carried out immediate safety and structural checks following the tremor.
"(We) confirmed that its safety and structural integrity remain unaffected," TNB said in a statement to Malaysiakini.
It added that no structural damage, cracks, or abnormalities were detected, while all monitoring and instrumentation systems were functioning normally.
It added that Temenggor Dam and other TNB-managed dams were designed to withstand seismic loading and were equipped with Strong Motion Accelerographs to monitor seismic activity.
Water levels, spillway operations and power generation also remained within safe parameters and were being continuously monitored by TNB's technical teams, it said.
Not the first time
This isn't the first time earthquakes have been detected around the dam, which was built between 1967 and 1974.
Nizarulikram said research had linked weak earthquakes around Temenggor to the filling of the reservoir following the completion of the dam in the late 1970s.
He said that according to earlier data, the Temenggor area had recorded at least five weak earthquakes since the 1980s.
"The weight and pressure of the large volume of water in the reservoir could place considerable stress on the rock beneath the lake.
"A substantial drop in the reservoir's water level could also trigger an earthquake," he said, as the underlying rock releases energy after being relieved of the weight of water it had previously supported.
Perak Science, Environment and Green Technology Committee chairperson Teh Kok Lim said in a statement on Friday that studies of potentially active fault structures around Temenggor indicated that any earthquakes were expected to be of low to moderate magnitude.
But Temenggor isn't the only dam along Sungai Perak. There are also three other dams, namely Bersia, Kenering, and Chenderoh.
TNB said all its dams were designed to withstand seismic loading.
Reactivation of ancient fault
Nizarulikram said researchers had also linked the earthquakes near Temenggor to the possible reactivation of an ancient geological fault - the Banding Fault.
A study by Dony Adriansyah Nazaruddin and Helmut Duerrast, published in SN Applied Sciences in 2021, similarly found dense faults or geological lineaments around the reservoir.
Significantly, all four earthquake epicentres in Temenggor it studied were either on or close to the surface trends of these lineaments.
The researchers cautioned, however, that lineaments identified through satellite-derived terrain analysis could indicate possible faults but were not themselves confirmation of faults without ground verification.
Teh said in a statement on Friday that studies of potentially active fault structures around Temenggor indicated that any earthquakes were expected to be of low to moderate magnitude. - Mkini
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