Johor Earthquakes Prompt Calls to Review Malaysia's Building Rules and Protect Critical Facilities

Seven tremors put local earthquake risk in focus

Seven tremors recorded in Johor between August 24 and 31, 2025, including a magnitude 4.1 earthquake near Segamat, have prompted calls for Malaysia to review seismic building standards, inspect vulnerable structures and improve maps of local earthquake hazards. Local authorities reported hairline cracks in buildings and fissures in the ground in scattered areas. No tsunami threat was issued, and monitoring continues.

The Malaysian Meteorological Department, known as MetMalaysia, recorded the sequence during a rare week of earthquake activity in the state. Weaker shocks were felt in Yong Peng, Kluang and Batu Pahat. For residents and building owners, the events brought a practical concern into view: whether structures built mainly to withstand everyday loads and wind can also cope with shaking from nearby faults.

Malaysia lies outside the Pacific Ring of Fire, a position that has encouraged the belief that the peninsula faces no earthquake danger. Its earthquake history tells a more complicated story. Sabah has experienced stronger earthquakes, including the 2015 Ranau event, which damaged dozens of buildings. Smaller earthquakes have been recorded over decades around Bukit Tinggi, Kuala Pilah, Kenyir, Manjung and Temenggor in Peninsular Malaysia.

Distant earthquakes in Sumatra and the Philippines can also send tremors across the region. Engineers and geologists say the Johor cluster shows that local faults can become active again, making the peninsula's seismic risk low but real.

Nor Shahidah Mohd Nazer, an engineering geology and soil mechanics expert at Universiti Kebangsaan Malaysia, urged a policy shift toward targeted upgrades in areas with greater hazards, with essential lifelines receiving priority. She described preparedness as a task guided by past events and present measurements.

We can't predict earthquakes, but we can prepare for their possibility based on both historical records and current data.

What happened during the Johor sequence?

Geoscientists identify renewed movement along the Mersing fault as the likely trigger of the Segamat earthquake sequence. Researchers at Universiti Teknologi Malaysia say the pattern of a main earthquake followed by smaller shocks signals reactivation and calls for deeper fault mapping and more instruments to measure activity.

The sequence included the following developments:

• August 24: A magnitude 4.1 mainshock occurred near Segamat in northern Johor.
• After the mainshock: Aftershocks of magnitude 2.8 and 3.2 followed.
• August 24 to 31: MetMalaysia recorded seven tremors across the week.

Johor's hard, ancient crust allows earthquake energy to travel farther without losing strength. That helps explain why shaking was reported beyond the area around the epicenter, including in Kluang, Muar and parts of Melaka. The epicenter is the point on the surface above where an earthquake begins underground.

Malaysia has several known old fault systems, including the Bentong–Raub suture zone, Bukit Tinggi–Genting, Manjung–Sungai Perak and the Kenyir area. Seismic engineering specialists caution that stress transferred from large earthquakes in Sumatra or the Philippines can nudge these older faults into movement.

Studies identify a corridor between latitudes two and four degrees north with higher peak ground acceleration values than other parts of the peninsula. It covers Klang, Kuala Lumpur, Seremban, Melaka, Muar, Batu Pahat, Segamat and Kluang. Peak ground acceleration, or PGA, describes how sharply the ground accelerates during shaking and helps engineers calculate the forces a building may face.

How Malaysia's seismic rules developed

Malaysia brought earthquake resistant design into mainstream building practice after the 2015 Ranau earthquake. The Malaysian National Annex to Eurocode 8, MS EN 1998-1, was introduced in 2017 to set out how buildings should be designed for ground shaking.

The Uniform Building By-Laws incorporate seismic provisions, but implementation depends on states formally gazetting the amendments. Engineering bodies say adoption remains uneven. A national design framework therefore still relies on state action and enforcement by local authorities to shape what happens on individual construction sites.

Industry estimates put the extra cost of complying with seismic provisions in new projects at roughly 5 to 15 percent of construction budgets. The amount depends on the building type and site conditions. Retrofitting an existing structure can be more complicated and may sometimes require occupants to leave temporarily while work takes place.

Eurocode 8 focuses on life safety. Buildings must resist the sideways forces created by earthquake shaking and deform in a controlled way without collapsing. Engineers call that ability ductility: a structure can bend and absorb energy rather than break suddenly.

The code sets detailed requirements for columns, beams and the joints connecting them. These parts must work together to absorb earthquake energy. In many cases, engineers must also carry out dynamic analysis, a calculation of how a building will move and sway during a quake.

Local ground conditions form another part of the design. Soft soil can increase shaking compared with rock, so the same structural design may face different demands at different sites. A building's safety depends on both its construction and the ground beneath it.

Adapting Eurocode 8 to Malaysian conditions

Malaysia's national annex adjusted parts of Eurocode 8 to local circumstances. Researchers identified limited local seismic data as a challenge and recommended a minimum hazard level to avoid designs that were too weak.

They also proposed a more practical method of classifying sites through the site's natural period. This describes the rhythm at which the ground tends to respond to shaking and helps represent how different soils behave during an earthquake.

Many local engineers were unfamiliar with ductile detailing, the construction details that allow structural parts to bend and absorb energy safely. Simplified tools were therefore developed for reinforced concrete design under Ductility Class Medium, or DCM.

A benchmarking approach called the Generalised Force Method was introduced to help validate dynamic models. Such checks help engineers assess whether their calculations of a building's movement are reliable. Together, the minimum hazard recommendation, soil classification approach, concrete design tools and model checks addressed practical difficulties in applying the seismic framework locally.

Older buildings face different challenges

Many buildings constructed before 2015 followed British Standards and were designed for wind and notional lateral loads, meaning assumed sideways forces used in design. Some have enough built in lateral stiffness to tolerate small tremors.

Stronger local shaking creates greater concern where buildings lack ductile detailing, have soft first stories or contain reinforced concrete frames filled with brittle masonry. A soft first story is a lower level that offers less resistance to sideways movement than the floors above. These features can produce damage patterns seen in moderate earthquakes around the world.

Engineers can strengthen older structures by adding braced frames or shear walls, which help resist sideways forces. Columns can be wrapped in fiber reinforced polymer or fitted with steel jackets. Floor diaphragms, the floor systems that transfer horizontal forces through a building, can also be connected more effectively to vertical walls.

Public sector projects have improved compliance under federal directives, while private sector compliance remains mixed. The Construction Industry Development Board has increased audits through the Quality Assessment System in Construction, known as Qlassix. Local authorities remain responsible for enforcing building codes.

Private owners can face financial and legal difficulties when upgrading older buildings. Redevelopment rules requiring broad consent for demolition and replacement can complicate decisions. Engineers recommend screening important buildings in areas with greater hazards and organising retrofits through a planned programme.

Engineers seek updated standards and rapid assessments

The Institute of Engineers Malaysia says the Johor tremors provide a timely reason to revise the national seismic design framework and align it with the new Second Generation Eurocode 8. Its leadership notes that older buildings designed mainly for wind often have some resistance to sideways forces, which can help during minor shaking.

Risk increases when the ground's movement matches a building's natural frequency, the rhythm at which it tends to sway. Repeated movement at that rhythm can make the swaying stronger. Structures with 10 to 20 stories can be more sensitive to local tremors, while very tall towers may respond more to large, distant earthquakes.

Site conditions matter as much as height. IEM recommends rapid assessments of hazards across cities after an earthquake is felt, allowing potentially vulnerable buildings to be identified and inspections prioritised.

The Housing and Local Government Minister has highlighted the resilience of newer towers, stating that high rises built since 2016 must meet stringent requirements and have been guided to resist strong shaking. All new government premises built after 2019 are required to be earthquake resistant.

Engineers explain that earthquake magnitude is not the parameter used to design a building. Magnitude describes the earthquake itself; structural design depends on the ground acceleration at a site and its design response spectrum. That spectrum describes the shaking demands on structures with different natural periods.

Changes to the Uniform Building By-Laws and updates to the national annex can improve consistency, while local authorities retain responsibility for enforcement. The calls for revised standards, updated mapping and assessments do not include a date for completing those changes.

Hospitals, schools and emergency services come first

Malaysian experts agree that hospitals, schools, dams, major bridges and emergency facilities should receive priority in any seismic upgrade programme. These facilities need to function during and after an earthquake, when communities may depend on them most.

Keeping a hospital or emergency building working requires more than a strong frame. Suspended ceilings and piping need restraints, generators and water tanks need secure anchors, and emergency exit routes need protection. Equipment failure or falling internal components can disrupt a building even when its main structure remains standing.

Structural frames also need robust detailing and more than one route for carrying loads. Engineers call this redundancy in load paths: if one element fails, other parts can share the load.

For new landmark or essential buildings, base isolation and other isolator systems can reduce the shaking that reaches the structure by filtering out part of the ground movement. Supplemental devices, including viscous or friction dampers, dissipate energy and can shorten the duration of shaking experienced by the building.

Retrofit choices include column jackets made from fiber reinforced polymers or steel, braced frames and shear walls. Careful stair connections, braced partition walls and secured mechanical and electrical equipment can limit damage and help a building stay operational.

Pipelines and tanks need flexible joints and anchorage to avoid ruptures. Engineers estimate that seismic measures for new buildings add about 5 to 15 percent to costs, while phased work on existing buildings can spread expenses and reduce disruption.

Better maps can guide building decisions

MetMalaysia operates a nationwide network of seismic sensors and coordinates with regional agencies. The Malaysian Tsunami Early Warning System can send earthquake alerts to the public within minutes of detection when a tsunami is possible.

The Department of Minerals and Geoscience has installed dozens of instruments to monitor local faults, including the Kuala Lumpur Fault in Selangor. Authorities published seismic hazard maps for Peninsular Malaysia, Sabah and Sarawak in 2019 to guide structural design and disaster planning.

Seismologists recommend updating those maps with 2025 datasets to account for both earthquake sources in Sumatra and local intraplate faults. Intraplate faults lie within a tectonic plate, rather than along its boundary, and can still generate earthquakes.

Experts also advocate microzonation in Johor Bahru, Segamat, Kluang, the Klang Valley, Melaka, Seremban, Ipoh and Penang. Microzonation maps earthquake hazards in smaller areas, capturing how soil conditions can increase shaking from one neighbourhood to another.

That detail feeds the peak ground acceleration values used in design. It can help engineers match new buildings and retrofits to the hazard at their actual location, while supporting decisions about which buildings need another inspection and how emergency services should plan their response.

Slopes, dams and roads also need attention

Even a moderate earthquake can destabilise slopes, especially around developments in highland areas. Geotechnical experts warn that shaking can trigger soil slippage and rockfalls, with heavy rain soon afterwards increasing the risk.

Local councils, dam operators and road authorities are urged to increase inspections for cracks, bulging walls, ground settlement and blocked drains. These checks extend earthquake preparedness beyond buildings to the land and infrastructure around them.

Slope reinforcement, effective drainage and retaining systems can reduce the risk of failure. Critical reservoirs and schools on hillsides need frequent visual checks and instruments that can detect movement early. Keeping drains clear is part of reducing the danger where shaking and rainfall affect the same slope.

Singapore reports no sensor alerts

Singapore's Building and Construction Authority reported that none of the tremor sensors installed on buildings in the country were triggered by the Johor earthquakes. Its buildings follow international codes adapted to local conditions.

Agencies across the straits continue to monitor seismic developments and review safety frameworks. The Johor events bring attention to the value of sharing earthquake data across borders and using compatible design practices in a closely connected region.

Practical steps for residents and building owners

Community advocates say public awareness remains low despite advances in monitoring and professional standards. Building managers can review safety plans and check whether essential equipment is anchored, while owners of older properties in corridors with greater hazards can ask qualified engineers about screening and retrofit options.

Residents, schools, workplaces and local authorities can take the following steps:

• Practise Drop, Cover, Hold On during drills and teach it to children and staff.
• Secure tall furniture, water heaters and heavy equipment to walls or floors.
• Prepare an emergency kit containing water, food, a torchlight, batteries, medication and first aid supplies.
• Know exit routes, avoid lifts during tremors and identify outdoor assembly points.
• Check walls, columns and stairs for new cracks after an earthquake is felt, and call professionals when uncertain.
• Review building documents to confirm seismic provisions for projects built after 2016.
• Consider a rapid visual assessment by a structural engineer for older buildings near mapped faults.
• Run evacuation drills in schools and workplaces and share safety information regularly.
• Prioritise local authority inspections of hospitals, schools, bridges and dams.

For Malaysia, the immediate priorities are concrete: identify vulnerable structures, protect facilities needed during emergencies, refine local hazard information and make existing design requirements more consistent in practice. The Johor sequence has brought those tasks into sharper focus without changing the need to match each building's response to its location, structure and ground conditions.

Key Points

• MetMalaysia recorded seven Johor tremors between August 24 and 31, 2025, including a magnitude 4.1 earthquake near Segamat.
• Local authorities reported hairline building cracks and ground fissures. No tsunami threat was issued.
• Geoscientists identify reactivation of the Mersing fault as the likely trigger of the sequence.
• Malaysia introduced its National Annex to Eurocode 8 in 2017, but state adoption and local enforcement remain uneven.
• Engineers seek updated standards, hazard maps using 2025 data and detailed mapping of local soil effects.
• Seismic measures for new buildings are estimated to add 5 to 15 percent to construction costs.
• Hospitals, schools, dams, bridges and emergency facilities are priorities for assessment and upgrades.
• Singapore reported no triggered building tremor sensors, while regional monitoring continues.
• Residents and managers can secure equipment, practise earthquake drills and arrange professional checks of potentially vulnerable buildings.