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In the early afternoon of 22 February 2011, a magnitude 6.3 earthquake devastated the bustling city of Christchurch, the largest city in New Zealand’s south island. It was one of the deadliest quakes in the country, taking the lives of 185 people. Just a few months later, on 13 June, another magnitude 6.4 aftershock earthquake further damaged the city’s infrastructure and buildings.
As New Zealand sits on top of two colliding tectonic plates—the Pacific and Australian plates— earthquakes are a common occurrence. Every year, the country experiences about 20,000 earthquakes, although many of them are minor and detected only by seismographs. That said, an estimated 250 earthquakes are still intense enough to be felt.
As such, New Zealanders are well aware of the importance of building structures that can withstand the power of earthquakes. If you’re a new homeowner or you’re planning to build your dream house in New Zealand, you need to make sure that the home you’re building is strong enough to withstand the devastating forces of Mother Nature. Here are some tips to make sure your home is resilient enough for New Zealand’s regular tremors.
Research Your Lot’s Location
If you’re buying a lot upon which to build your home, you have to do your homework to find out if the location is prone to disasters such as earthquakes. Is it close to a known fault line? What’s the history of earthquakes in the area? Have there been major earthquakes in the past that damaged homes? These are just some of the more important questions to ask before finalising the deal.
You can check New Zealand’s Seismic Resilience site to know where the earthquake risk zones are. The areas close to the Alpine fault line are considered to be high-risk zone 4, while Dunedin is classified as zone 1 or one of the safest areas in terms of seismic activity. That said, even if you live in Dunedin, it’s still prudent to hire a Dunedin builder who specialises in earthquake-resistant homes; the South Island has had its share of strong earthquakes in the past and you have to be ready for any situation.
For a better understanding of your property’s location, have it assessed by a professional. In doing so, you can avoid expensive damages and increased insurance costs on your property.
Design a Foundation Optimised for Earthquakes
A resilient foundation is the bedrock of earthquake-proof homes. As such, explore innovations for reinforcing your house’s structure like base isolation, cross braces, and diaphragms. These help optimise a structure for seismic events.
Remember, a well-designed foundation is not merely a structural element; it is also a robust shield that stands strong against the earth’s unpredictable movements.
Invest in Damping Systems
Damping systems are vital features of earthquake-resistant homes. These innovative technologies absorb and dissipate seismic energy, thus preventing or minimising damage to a structure.
In 2021, a study was conducted to find out if small fluid dampers can effectively protect a home from earthquakes. To test the dampers, a two-storey house was subjected to 85 per cent of the foreshock records of the 2016 Kumamoto earthquake in Japan, among other earthquake scenarios. The results concluded that even small fluid dampers can protect a multi-storey house from major damage during a quake.
Build Adequate Drainage
In the battle against earthquakes, don’t underestimate the power of water. Adequate drainage is your frontline defence against soil liquefaction, a phenomenon that can turn solid ground into a quagmire during seismic events.
In the recent Japan earthquake that occurred on New Year’s Day of 2024 at the Noto Peninsula of Ishikawa Prefecture, liquefaction played a huge role in the damage to the streets and houses in the area. Asphalt roads were cracked, entire homes were shifted, and electric poles were toppled to the ground. According to preliminary reports, most of the damage may be attributed to liquefaction after the tremors.
This highlights the importance of incorporating permeable surfaces and effective water management strategies in building your home, to ensure that it remains stable even in the face of nature’s wrath.
Strengthen Connections
The strength of a chain is defined by its weakest link—and the same holds true for earthquake-resistant homes. Reinforce the connections between various components, such as the walls to the foundation, to eliminate weak points that could lead to disproportionate damage. Every bolt, beam, and joint plays a crucial role in fortifying your home against seismic forces.
Utilise Shear Walls
For those unfamiliar, a shear wall is a form of structural support that protects against shear forces, like strong winds or earthquakes. Simply put, shear walls are vital structures for any earthquake-resistant design. They essentially add an extra layer of defence,absorbing the compression and tension generated during the earthquake and quickly transferring them to the foundation
Choose Ductile Materials
Flexibility is key when it comes to earthquake-resistant materials, so choose ductile materials that can deform without breaking. Steel is a prime example of these, bringing both strength and flexibility to the table. Used in a variety of structural components, steel ensures your home remains resilient against sudden shaking. Another example is reinforced concrete or concrete with reinforcement bars. The concrete combined with steel bars produces a material that’s stiff, strong, and incredibly ductile, making it a must-have material for an earthquake-resistant structure.
Building an earthquake-proof house in an earthquake-prone country like New Zealand is a challenge, to say the least. However, these drawbacks can be overcome with knowledge and proper preparation to ensure that your house will withstand major earthquakes and other forces Mother Nature may decide to hit you with.