Navigating Seismic Engineering in Australia: Understanding Earthquake Risk and Design Requirements

Australia is often considered a relatively stable continent, but earthquakes can and do occur across the country. Although Australia’s seismic conditions differ from those experienced in highly active tectonic regions, earthquake actions remain an important consideration in Australian building design.

Seismic engineering in Australia involves assessing how buildings, building services and non-structural components may respond to earthquake ground movement. Engineers use this information to design structures and restraint systems that reduce the risk of collapse, falling components, service failures and disruption following a seismic event.

Australian seismic design is governed through a combination of:

• The National Construction Code

• AS 1170.4, Structural design actions – Earthquake actions in Australia

• Referenced Australian Standards

• State and territory building legislation

• Building Importance Levels

• Site conditions and seismic hazard factors

• Project-specific engineering requirements

Unlike New Zealand, Australia does not generally use PS1 producer statements, percentage-based New Building Standard ratings or nationwide earthquake-prone building classifications.

Instead, earthquake requirements are assessed through the Australian structural design and building certification framework.

What Is Seismic Engineering?

Seismic engineering is the area of structural and building-services engineering concerned with the effects of earthquakes on buildings, equipment and infrastructure.

It may involve the design or assessment of:

• Complete building structures

• Structural frames

• Walls and bracing systems

• Building façades

• Parapets and appendages

• Ceilings and partitions

• Mechanical equipment

• Electrical equipment

• Pipework

• Ductwork

• Cable trays

• Fire-protection services

• Storage systems

• Architectural components

The purpose of seismic design is not necessarily to prevent every form of damage.

Instead, the design objective generally focuses on reducing risks to life, maintaining structural stability and, for important buildings and essential systems, improving operational resilience following an earthquake.

Does Australia Have Earthquake Risk?

Earthquake hazard exists throughout Australia, although the expected level of ground shaking varies by location.

Geoscience Australia’s National Seismic Hazard Assessment identifies regional variations in the likelihood and intensity of earthquake ground shaking. This information helps engineers, authorities and emergency planners identify areas where stronger shaking may be more likely and develop appropriate risk-mitigation strategies.

Australian earthquakes occur within the Indo-Australian tectonic plate rather than primarily along a nearby plate boundary. Because faults within the continent can be difficult to identify and may remain inactive for long periods, damaging earthquakes can occur in areas without frequent recent seismic activity.

For this reason, earthquake design should not be dismissed simply because a building is located away from a well-known fault or historical earthquake zone.

Earthquake Design Under the National Construction Code

The National Construction Code requires buildings and structures to perform adequately under reasonably expected design actions, including earthquake actions.

For relevant Australian buildings, the NCC references AS 1170.4 as the primary standard for determining earthquake design actions.

The NCC framework considers matters such as:

• Building classification

• Importance Level

• Annual probability of exceedance

• Structural system

• Geographic hazard

• Site conditions

• Building height

• Component location

• Consequences of failure

Earthquake requirements are not limited to the primary building frame. Certain non-structural building components may also need to resist horizontal and vertical seismic forces.

These can include ceilings, partitions, appendages, mechanical equipment, electrical systems, fire-suppression systems and smoke-control equipment.

AS 1170.4: Earthquake Actions in Australia

AS 1170.4, Structural design actions – Earthquake actions in Australia, provides procedures for determining earthquake actions on Australian buildings and building components.

The standard is used alongside the broader AS/NZS 1170 structural design actions series.

AS 1170.4 addresses matters including:

• Earthquake hazard factors

• Site subsoil conditions

• Building Importance Levels

• Structural ductility

• Building height

• Structural response

• Earthquake design categories

• Non-structural building components

• Mechanical and electrical services

• Architectural elements

The NCC 2022 referenced-documents schedule currently identifies AS 1170.4:2007, incorporating Amendments 1 and 2, as the referenced earthquake-actions standard.

The engineer should confirm the edition applicable to the particular building approval, contract and jurisdiction before completing the design.

Seismic Hazard Factors

Australian earthquake design does not rely on a simple list of “safe” and “unsafe” locations.

Instead, a seismic hazard factor is used to represent the expected earthquake hazard associated with the building’s geographic location.

This factor forms part of the calculation used to determine earthquake design forces.

Geoscience Australia publishes seismic hazard information showing how expected ground shaking varies across Australia. However, a higher regional hazard is only one part of the overall engineering assessment.

The final seismic design requirements can also be influenced by:

• Building Importance Level

• Site subsoil class

• Structural form

• Building height

• Component weight

• Component mounting height

• Structural ductility

• Equipment function

• Consequences of failure

A building in a lower-hazard region may still require seismic design, particularly if it is an important facility or contains heavy, elevated or safety-critical equipment.

Building Importance Levels

The National Construction Code assigns buildings and structures an Importance Level based on the consequences of failure and their importance to the public.

Importance Levels generally range from 1 to 4.

Importance Level 1

Importance Level 1 typically applies to structures presenting a low risk to life and property if they fail.

Examples may include certain minor or infrequently occupied structures.

Importance Level 2

Importance Level 2 commonly applies to ordinary buildings that do not fall within the lower- or higher-risk categories.

Many residential, commercial and industrial buildings are assessed at this level.

Importance Level 3

Importance Level 3 may apply where a building contains large numbers of people, vulnerable occupants or functions that have a substantial public impact.

Examples may include certain schools, assembly buildings and healthcare facilities.

Importance Level 4

Importance Level 4 applies to buildings and infrastructure with critical post-disaster functions or extreme consequences of failure.

Examples may include emergency facilities and other essential infrastructure.

Higher Importance Levels generally correspond with more stringent design events and greater expectations for structural and non-structural performance.

Earthquake Design Categories

AS 1170.4 uses earthquake design categories to determine the level of analysis and detailing required for a building.

The applicable category depends on several factors, which may include:

• Building Importance Level

• Earthquake hazard factor

• Site subsoil class

• Structural system

• Building height

• Structural ductility

A lower design category may permit simplified design methods.

Higher categories may require more detailed structural analysis, specific detailing and closer consideration of the building’s seismic-resisting system.

The earthquake design category should be established by the project structural engineer rather than assumed based only on geographic location.

Site Subsoil Conditions

The type of ground beneath a building can significantly influence how earthquake shaking affects the structure.

Soft or deep soils may amplify certain ground motions compared with shallow rock or stiff ground.

Seismic design may therefore consider a site subsoil classification based on factors such as:

• Soil type

• Rock depth

• Soil stiffness

• Geological profile

• Geotechnical investigation

• Groundwater conditions

The geotechnical engineer and structural engineer may need to coordinate when establishing the appropriate site classification.

Using an incorrect soil class can affect the calculated earthquake forces and structural response.

Structural Seismic Design

Structural seismic design examines how the primary building structure will resist earthquake actions.

The engineer may assess:

• Lateral load-resisting systems

• Braced frames

• Moment-resisting frames

• Shear walls

• Diaphragms

• Building torsion

• Structural irregularities

• Connections

• Foundations

• Structural ductility

• Load paths

A continuous load path is essential.

Earthquake forces must be transferred through floors, roofs, walls, frames and foundations without relying on weak or discontinuous connections.

Structural irregularities, such as major changes in stiffness, offset walls or discontinuous bracing, may require more detailed analysis.

Seismic Design of Non-Structural Components

Non-structural components can create serious hazards during an earthquake even where the primary building frame remains stable.

These components may include:

• Suspended ceilings

• Internal partitions

• Parapets

• Façade elements

• Mechanical equipment

• Electrical switchboards

• Ductwork

• Pipework

• Cable trays

• Fire-suppression systems

• Storage racks

• Architectural features

The Australian Building Codes Board notes that poorly restrained non-structural elements can injure occupants, rupture sprinkler pipework, damage electrical equipment, block exits and make a building unusable after an earthquake.

Section 8 of AS 1170.4 provides methods for determining earthquake actions on specified non-structural parts and components.

Seismic Restraint of Mechanical Equipment

Mechanical equipment may require seismic restraint because of its mass, mounting arrangement or importance to building operation.

Equipment that may require assessment includes:

• Air-handling units

• Chillers

• Cooling towers

• Condensers

• Fans

• Pumps

• Boilers

• Heat exchangers

• Packaged air-conditioning units

• Rooftop plant

• Mechanical control panels

Restraint systems may include:

• Steel brackets

• Support frames

• Bracing rods

• Seismic cables

• Mechanical anchors

• Direct structural fixings

• Proprietary restraint systems

The engineer must consider the complete load path from the equipment through the restraint and anchors into the primary building structure.

Seismic Restraint of Ductwork

Suspended ductwork can move in both transverse and longitudinal directions during an earthquake.

Where seismic restraint is required, the design may include:

• Transverse braces

• Longitudinal braces

• Strengthened trapeze supports

• Bracing rods

• Seismic brackets

• Structural anchors

• Flexible connections

• Clearance from adjacent services

Ductwork restraint should be coordinated with:

• Fire dampers

• Flexible duct connections

• Ceiling systems

• Structural beams

• Other mechanical services

• Maintenance access

Bracing should be connected to an adequate structural element rather than lightweight ceiling framing or other non-structural construction.

Seismic Restraint of Pipework

Pipework can be vulnerable to joint damage, excessive movement and rupture during an earthquake.

Services that may require seismic restraint include:

• Fire-sprinkler pipework

• Hydrant pipework

• Chilled-water services

• Heating-water systems

• Plumbing pipework

• Gas services

• Medical-gas systems

• Process pipework

A seismic restraint system may use:

• Transverse braces

• Longitudinal braces

• Anchors

• Guides

• Flexible couplings

• Seismic separation joints

The design must balance earthquake restraint with allowances for thermal expansion and normal service movement.

Seismic Restraint of Electrical Services

Electrical equipment can create safety, fire and operational risks if it moves or overturns during an earthquake.

Equipment that may require restraint includes:

• Main switchboards

• Distribution boards

• Transformers

• Battery cabinets

• Uninterruptible power supplies

• Generators

• Cable trays

• Busduct

• Communications racks

• Control cabinets

• Emergency-power systems

Tall cabinets and equipment with a high centre of gravity may be particularly susceptible to overturning.

The engineer may assess the equipment weight, centre of gravity, base connection, anchor arrangement and supporting structure.

Fire and Life-Safety Systems

Seismic restraint is especially important where failure could compromise fire safety or emergency response.

Relevant systems may include:

• Fire-sprinkler pipework

• Fire pumps

• Smoke-control equipment

• Emergency electrical systems

• Fire-alarm panels

• Hydrant services

• Emergency communications

• Exit-path components

Failure of a life-safety service during an earthquake can create secondary hazards, including fire, flooding, loss of emergency lighting or obstruction of evacuation routes.

These systems may therefore require more careful coordination and restraint than ordinary non-essential services.

Seismic Design of Ceilings and Partitions

Suspended ceilings, partitions and overhead architectural elements can fall or separate during earthquake movement.

Seismic design may need to consider:

• Ceiling mass

• Suspension layout

• Perimeter clearances

• Bracing

• Bulkheads

• Light fittings

• Air diffusers

• Access panels

• Partition connections

• Interaction with other services

Heavy fittings supported by a ceiling grid may require independent structural support.

Ceiling restraint must also be coordinated with mechanical, electrical and fire services passing through the ceiling space.

Seismic Anchors and Structural Fixings

Seismic restraint systems depend on anchors and structural fixings capable of transferring design forces into the building structure.

Common fixing systems include:

• Mechanical expansion anchors

• Concrete screw anchors

• Undercut anchors

• Bonded anchors

• Cast-in anchors

• Structural bolts

• Beam clamps

• Welded connections

Anchor design may need to consider:

• Tension and shear

• Cracked concrete

• Concrete breakout

• Pull-out

• Edge distances

• Anchor spacing

• Embedment depth

• Fixture thickness

• Cyclic loading

• Installation conditions

An anchor should not be selected based only on equipment weight or static pull-out capacity.

The anchor, bracket, brace, equipment support and primary structure must work together as one engineered system.

Seismic Engineering for Existing Buildings

Existing buildings may require seismic assessment where:

• The building is being substantially altered.

• New heavy equipment is being installed.

• The building use is changing.

• Structural damage has occurred.

• Original drawings are unavailable.

• Existing restraints appear inadequate.

• Critical services are being upgraded.

• A building certifier requests further evidence.

An existing-building assessment may involve:

• Reviewing original structural drawings

• Site inspections

• Measuring structural elements

• Investigating connections

• Material testing

• Structural analysis

• Assessing non-structural components

• Identifying strengthening options

Unlike New Zealand, Australia does not generally assign existing buildings a nationwide percentage-based seismic rating such as a percentage of New Building Standard.

The assessment method and reporting format depend on the project scope, jurisdiction and reason for the review.

Seismic Strengthening and Retrofitting

Seismic strengthening improves the capacity or performance of an existing building or component.

Strengthening measures may include:

• Adding structural bracing

• Installing new shear walls

• Strengthening diaphragms

• Improving wall-to-roof connections

• Restraining parapets

• Adding equipment anchors

• Bracing building services

• Strengthening support frames

• Replacing inadequate fixings

• Providing flexible service connections

The preferred solution depends on the existing structure, expected earthquake actions, building use, access constraints and project budget.

The engineer should also consider whether strengthening one area changes the distribution of forces elsewhere in the building.

Seismic Risk Versus Seismic Hazard

Seismic hazard and seismic risk are related but different concepts.

Seismic hazard describes the likelihood and potential intensity of earthquake ground shaking at a location.

Seismic risk considers the consequences of that shaking.

Risk may be influenced by:

• Building vulnerability

• Occupant numbers

• Building function

• Equipment importance

• Construction quality

• Age and condition

• Emergency response requirements

• Economic consequences

• Potential disruption

A location with moderate seismic hazard may still have significant risk where a vulnerable or essential building is involved.

Conversely, a well-designed building in a higher-hazard area may have a lower level of vulnerability.

Earthquake Monitoring in Australia

Geoscience Australia operates national earthquake monitoring and hazard-assessment resources.

Seismic instruments record ground motion and help scientists identify earthquake locations, magnitudes and shaking characteristics.

This information contributes to:

• National seismic hazard assessments

• Earthquake research

• Emergency response

• Engineering guidance

• Risk modelling

• Public information

Real-time earthquake monitoring does not replace engineering design. It provides scientific information that helps improve the understanding of Australian earthquake hazards over time.

Seismic Engineering Assessments

A seismic engineering assessment may examine the building structure, individual components or both.

Depending on the project, the assessment may include:

• Establishing the applicable seismic design criteria

• Reviewing the building Importance Level

• Determining the site hazard factor

• Reviewing subsoil conditions

• Calculating component earthquake forces

• Inspecting existing supports

• Checking anchors and connections

• Identifying unrestrained services

• Preparing strengthening recommendations

• Producing certification documentation

For building-services projects, the assessment often begins with equipment schedules showing weights, dimensions, locations and support arrangements.

Accurate equipment information is necessary because seismic forces are directly influenced by the component’s mass and position within the building.

Site-Specific Seismic Engineering

Generic restraint details may be useful for standard installations, but they cannot automatically be applied to every project.

Site-specific seismic engineering may be required where:

• Equipment weights exceed generic limits.

• Support spacing differs from the standard detail.

• Equipment is mounted at a higher level.

• The building has a higher Importance Level.

• The supporting substrate is different.

• Vibration isolators are used.

• Anchor edge distances are restricted.

• Services are congested.

• Equipment has a high centre of gravity.

• The installation falls outside proprietary-system limitations.

A site-specific design should reflect the actual project drawings, equipment and structural support conditions.

Engineering Certification for Seismic Design

Seismic engineering certification varies between Australian jurisdictions.

The certification package may include:

• Seismic calculations

• Equipment schedules

• Bracing layouts

• Anchor schedules

• Support details

• Certified engineering drawings

• Installation requirements

• Design assumptions

• Inspection requirements

• Engineering certificates

In Queensland, the design may be supported by a Form 15 Compliance Certificate for Building Design or Specification where applicable.

In Victoria, a Regulation 126 Certificate of Compliance may be used for proposed building work where the relevant requirements are satisfied.

Other states and territories use their own engineering certification processes and terminology.

The required certificate should be confirmed with the building certifier or relevant building surveyor before documentation is prepared.

Seismic Inspection and Construction Verification

Inspection helps confirm that seismic restraints have been installed in accordance with the certified design.

An inspection may review:

• Equipment weights and locations

• Brace type and arrangement

• Brace angles

• Anchor types

• Anchor diameter

• Embedment

• Edge distances

• Support spacing

• Structural fixing points

• Equipment connections

• Flexible joints

• Differences from the approved drawings

Critical restraints should be inspected before ceilings, linings or other finishes conceal them.

Where a physical site inspection is not possible, the engineer may request:

• Clear installation photographs

• Marked-up drawings

• Anchor installation records

• Product information

• Installer declarations

• As-built measurements

The appropriate evidence depends on the project and certification requirements.

Common Seismic Design and Installation Issues

Common seismic-engineering problems include:

• Assuming earthquake design is unnecessary in Australia

• Using equipment weight without checking mounting height

• Fixing braces to non-structural elements

• Installing anchors too close to concrete edges

• Using unsupported generic details

• Failing to restrain vibration-isolated equipment

• Omitting flexible service connections

• Bracing in only one direction

• Ignoring the supporting structure

• Changing equipment without updating the design

• Installing braces at incorrect angles

• Concealing restraints before inspection

Early coordination can prevent many of these issues.

Why Early Seismic Coordination Matters

Seismic requirements should be considered before building services are installed.

Early seismic coordination allows the design team to:

• Identify components requiring restraint

• Obtain accurate equipment weights

• Confirm suitable fixing locations

• Coordinate brace positions

• Avoid clashes with other services

• Select suitable anchors

• Strengthen supports where required

• Establish inspection hold points

• Include seismic costs in project planning

• Prepare appropriate certification documentation

Attempting to add seismic restraint after services have already been installed can lead to congestion, unsuitable fixing points and costly rework.

Frequently Asked Questions

Is seismic design required in Australia?

Earthquake actions form part of the Australian structural design framework. The extent of the required design depends on the NCC, AS 1170.4, building Importance Level, location, site conditions and building or component characteristics.

Is all of Australia considered a seismic area?

AS 1170.4 applies earthquake hazard factors across Australian regions. The level of seismic hazard varies, but earthquake actions should not be ignored solely because a project is located outside a recognised high-hazard area.

What standard covers earthquake design in Australia?

AS 1170.4, Structural design actions – Earthquake actions in Australia, is the principal Australian Standard referenced by the NCC for earthquake actions.

Does Australia use seismic building ratings?

Australia does not generally use New Zealand’s percentage of New Building Standard rating or C1 and C2 earthquake-prone building classifications. Australian assessments use the NCC, AS 1170.4 and project-specific engineering criteria.

What building services may require seismic restraint?

Mechanical equipment, ductwork, pipework, cable trays, electrical equipment, fire-protection systems, ceilings and other non-structural components may require seismic assessment or restraint.

Does every air-conditioning unit require seismic bracing?

Not necessarily. The requirement depends on factors such as equipment weight, building Importance Level, mounting height, support conditions and the exemptions or criteria within the applicable design standard.

Can generic seismic details be used?

Generic details may be suitable where the installation remains within all stated design limits. Site-specific engineering is required where the equipment, building or support conditions fall outside those limits.

What certification is provided for seismic engineering?

Certification varies by state. Queensland may use Form 15, while Victoria may use Regulation 126 certification. Other jurisdictions have their own engineering documentation and approval requirements.

Building More Resilient Australian Structures

Seismic engineering is an important part of Australian structural design and building-services coordination.

Although Australia’s earthquake environment differs from New Zealand’s, buildings and non-structural components must still be assessed against the earthquake actions applicable to their location, function and construction.

Effective seismic design considers more than the building frame. Mechanical equipment, electrical systems, pipework, ductwork, ceilings, partitions and life-safety services must also be reviewed where their failure could injure occupants or compromise building operation.

By applying the National Construction Code, AS 1170.4 and appropriate state-specific certification requirements, engineers can develop practical seismic restraint and structural solutions that improve safety, protect essential services and increase the resilience of Australia’s built environment.