Inspections more of worry than shakes

By Morgan Tait, Doug Laing


Two earthquakes which have shaken Hawke's Bay less than 48 hours apart came either side of a meeting at which property owners were more worried about threats posed by building risk assessments than the potential of the big shake.

The second quake at 12.42pm yesterday registered 5.5 magnitude, and, centred 10km northeast of Taupo was widely felt throughout the region and as far away as Christchurch and Auckland.

It came less than 48 hours after a magnitude 5.2 quake at 1.05pm on Monday that was centred 15km southeast of Tokoroa at a depth of 195km.

Both were about the same time of the day as the major Canterbury earthquake at 12.51pm on February 22, 2011, also a working day when many people were at their most vulnerable in multi-storey office blocks, or susceptible to falling masonry and other debris in streets immediately outside.

Ironically, between this week's two quakes, a major forum was held early on Monday night in Napier amid worries about the future for buildings being assessed as earthquake prone, threatening investments and retirement income, and the city's valuable Art Deco heritage.

Yesterday, people who had been at the meeting in St John's Cathedral appeared less concerned about the possibility of bigger earthquakes after the latest shakes than the threats posed by burgeoning quake-risk assessments, which one building owner described as a "vast over-reaction".

GNS Science duty seismologist John Ristau said there was nothing unusual about the quakes on Monday and yesterday.

"Deep, moderate size earthquakes like this are not uncommon in the North Island," he said. "A 195km deep magnitude 5.2 earthquake occurred on October 15, although the two are not related."

Hawke's Bay residents were quick to turn to social media to report their earthquake experiences - "rolling motion" and "good shake" featuring. Christine Kinder in Onekawa had fears: "I live on the old dump, I thought 'here we go I'm going to sink'," she said.

Others reported ducking for cover, their cars rocking and motivation to update their emergency kits.

Mr Ristau said GeoNet received about 5000 "felt" reports from all over the North Island and upper South Island from Auckland to Canterbury and Taranaki to Hawke's Bay.

"As the seismic waves leave the epicentre they have to travel some distance through the Earth before they reach the surface. The seismic waves then travel along the surface and this is what people feel strongly."

Hawke's Bay was especially susceptible to feeling quakes as the Australian tectonic plate is pushed by the Pacific plate beneath; along the east coast of the North Island.

"The seismic waves travel very efficiently along the boundary between these two plates and as a result the earthquakes are often felt very strongly to the east of where they occurred, ie, Hawke's Bay, Wairarapa and Wellington.

"Deep earthquakes like these typically don't produce aftershocks, and if they do the aftershocks are much smaller than the main shock and are not felt due to their depth."

Monday night's forum attracted more than 200 people, which city councillor Mark Herbert and city council marketing agent Rick Hopkinson said was much more than they'd expected.

As well as building owners, it included tenants, neighbours of vulnerable buildings and others interested to keep up with developments, and councillors and council staff from Napier and Hastings.

The meeting was hosted by the Art Deco Trust and supported by the New Zealand Historic Places Trust, the national Institute of Architects, and councils.

Historic Places Trust central region manager Ann Neill said it was crucial for all key stakeholders to "come together" to develop response strategies and work together on assessment, management and preservation of at-risk buildings.

"The challenges and opportunities associated with strengthening, insurance and preservation is one of the biggest issues facing New Zealanders," she said.

Ms Neill said she hoped the forum would show the issues were "not insurmountable" and there remained a future for heritage buildings.

Key speakers at the forum were Auckland University Associate Professor of Structural Engineering Jason Ingram, and NZ Society for Earthquake Engineering chief executive Win Clark.

Napier Mayor Barbara Arnott said the forum was needed, and she looks forward to more as Canterbury disaster inquiry commission outcomes are known and more consistent engineering standards are formulated.

- Hawkes Bay Today

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