Imagine a scene straight out of the movie “San Andreas,” where Dwayne “The Rock” Johnson is racing against time to save his family from a massive earthquake. While the movie is set in California, the real-life potential for such a catastrophic event exists right here in New Zealand, centred around the Hikurangi Subduction Zone (running up the east coast of the North Island - basically Wellington to Gisborne). This region, along with the Cascadia Subduction Zone in North America and the Tohoku region in Japan, are capable or producing megathrust earthquake and tsunami risks. We explore the impact of the Tohoku earthquake to get a sense of what a rupture of the Hikurangi fault line might look like here in New Zealand.
Our very own Hikurangi Subduction Zone is where the Pacific Plate is subducting beneath the Australian Plate, off the east coast of New Zealand’s North Island. This tectonic boundary can generate earthquakes with magnitudes up to 9.0. The odds are quite terrifying with scientists estimating a 25% chance of a M8 quake or larger striking at the southern section of the Hikurangi subduction zone (beneath Wellington, Marlborough, and Wairarapa) within the next 50 years. Just like in “San Andreas,” where the characters are caught off guard by the sudden quake, the Hikurangi Subduction Zone has a history of both large earthquakes and slow slip events.
A major earthquake in the Hikurangi Subduction Zone could cause severe shaking across the North Island and the top of the South Island, along with a large tsunami. The potential human and economic toll is significant. Coastal communities, particularly those in Gisborne, Hawke’s Bay, and Wellington, would be at high risk. Picture the chaos and urgency seen in “San Andreas,” but right here in our own backyard. Fortunately, there has been, and continues to be, significant research by GNS Science and National Hazards Commission to better understand the fault and help implement measures to improve our resilience and emergency response.
We don't have to look to far to get a sense for the potential impact of a Hikurangi rupture than looking at the Tohoku M9.0 Earthquake in 2011. The earthquake occurred where the Pacific Plate is subducting beneath the North American Plate in an area known as the Japan Trench. This earthquake triggered a massive tsunami with waves reaching heights of up to 40 meters (133 feet), inundating coastal areas and causing significant loss of life and property. It led to the Fukushima Daiichi nuclear disaster and resulted in economic damage of upwards of a $200 billion. The tsunami also resulted in a death toll of approximately 19,700, with thousands more injured and missing.
Magnitude and Frequency All three regions are capable of producing extremely powerful earthquakes. All three regions have the potential for earthquakes with magnitudes of 9.0+. The frequency of these events varies, with Cascadia and Hikurangi having longer intervals between major quakes compared to the more seismically active Tohoku region.
Tsunami Risk Each region has a significant tsunami risk. The Tohoku earthquake in 2011 produced one of the most devastating tsunamis in recent history. Cascadia and Hikurangi also have the potential to generate massive tsunamis that could inundate coastal areas within minutes of an earthquake.
Impact Area The impact areas of these earthquakes differ. The Cascadia Subduction Zone affects a larger and more densely populated region in North America, including major cities like Seattle and Vancouver. The Hikurangi Subduction Zone’s impact is concentrated on New Zealand’s North Island, while the Tohoku region affects a densely populated and highly developed area of Japan.
Preparedness Japan’s preparedness measures are among the best in the world, yet the 2011 disaster showed that even the best systems can be overwhelmed. The Cascadia and Hikurangi regions are working on improving their resilience and emergency response capabilities.
Prepare and make your home safer and stronger for earthquakes. Talk with whānau and make a plan. Be familiar with your local civil defence emergency management group.
Most importantly, if you live near the coast and you experience a quake that is Long or Strong, Get Gone. If you’re near the coast, or a lake, and an earthquake of any size is long (shaking lasts more than a minute), or strong (it’s hard to stand up), then get gone to higher ground or inland immediately. Don't wait for any official announcement, just get moving.
For more information refer to GeoNet site.
The Hikurangi Subduction Zone represents a significant earthquake and tsunami risk for New Zealand, comparable to the threats posed by the Cascadia and Tohoku regions. While each region has unique characteristics and challenges, the potential for devastating earthquakes and tsunamis is a common thread. Ongoing research, improved preparedness, and resilient infrastructure are crucial to mitigating the devastating effects of these natural disasters. For New Zealand, understanding and preparing for the risks associated with the Hikurangi Subduction Zone is essential for safeguarding communities and ensuring a resilient future. And while we may not have "The Rock" to save the day, our forward planning and collective efforts can make a world of difference.
