Earthquake tonight

[Rob Beale]

That "Canoe" report is very good.

Tsunamis have hit Gisborne's coastal area often in the past. One in the 1940's hit just to the north and washed a bridge away as well as flooding a pub and destroying at least one house.

Since the Boxing Day Tsunami, scientists re-evaluated the threat to NZ and found that good old Gisborne is at worst risk. A major earthquake of magnitude 8 or more hitting in the same area as Thursdays quake could cause an undersea landslip into the Hikurangi trench which lies offshore, parallel to the axis of the island. The warning period is about 20 minutes!


Well Tony I think its time the Black Caps changed from cricket to some other game: I don't see how the sponsors justify their costs.

I took a walk through town yesterday to have a look. There are still 3 blocks cordoned off. Workers were removing loose masonry on some buildings. Two of the worst hit shops were victims of insecure neighbours - in one case a complete first floor wall fell through the roof of a single storey neighbour.

On the night of the quake we found a lump of masonry lying on the pavement 10 metres away from our car - the lump was the size of a stove! and had crashed through the verandah.

Rob

[Rob Beale]

Christchurch was hit this morning at 04:35 local time by an Earthquake of magnitude 7.1 (Originally reported as 7.4) The epicentre was close, at 30 km away.

Damage is extensive, but no loss of life, just 2 serious injuries so far.

The damage is generally older brick buildings, where the front walls have fallen out into the street and crushed cars below.
Usually the floors are still in place, so no collapses as happens overseas.

Lots of houses have lost their chimneys, and brick veneer walls have fallen off some timber framed houses

Watermain and sewer pipe damage in some places, so that has public health implications.

Reports are still coming in as day breaks and authorities inspect and assess the extent of the damage.

Christchurch is about 1000km away from my home, but all kiwis are well aware of the effects of earthquakes, and most have family or friends nin the area.

Best wishes to all MLU members in Christchurch

Rob

[Ryan]

Best of luck to all over the pond. Have been watching this on the news this morning. Very fortunate that no one was killed.

[Ken Hughes]

Hi there Rob,Did the earth move for you?,It did here in Brighton Dunedin,everything was swaying back and forwards,My step son and his good lady and grandchild live in central Christchurch city,they are still without power and water at 330 pm today,they are with friends with power etc for now and are ok

[Ganmain Tony]

Hope everyone and their trucks are not bent.

Stay safe all you Kiwi boys and girls.....

[Lynn Eades]

My cousin just told me that his (its a dream home) is wrecked. Built on a concrete slab, It is near the Avon river, and is therefore built on river silt and rock The whole lot has become liquid, and slumped, no doors or windows can be opened or closed. We feel for them, but can't do a thing for them.

[Rob Beale]

In Christchurch and the surrounding area the damage is widespread, but fortunately no deaths reported as yet after 24 hours. The worry is that not all buildings have been checked yet. A lot of the damage will be shown on TV news worldwide now.

The size of the city and its proximity to the epicentre, have resulted in the large number of damaged buildings.

Thanks to our long history of earthquakes since European settlement began in the 1850s, NZ building practice has modified the old English style of brick buildings which were built to withstand gravity and a bit of wind only.
The 1931 earthquake that destroyed Napier and Hastings prompted a major change, and now all building elements are tied together: walls, floors and ceilings. A lot of old buildings have been retrofitted with ties and bracing, and all modern structures have extensive bracing in all directions.

Most of the damage you have seen on TV is where curtain walls have broken free and collapsed, but you will see that the floors are still in place. This is important as the occupants are not crushed by falling floors and are able to be exacuated after the shake stops.

Decorative features like parapets are also likely to break free, hence all Kiwi kids are taught to never run outside, but to get under strong furniture, or into doorways to shelter during the shake. We wait till its over before getting out!
The big death tolls in overseas Earthquakes are due to buildings collapsing and the floors pancaking down on each other. (There is little hope of rescue then).

On the domestic scene, it is chimneys that fall frequently, and crash through ceilings. This is despite advice to homeowners over many years to strengthen the ceiling around chimneys. Most brick chimneys in NZ homes have been replaced by concrete ones, at least at the top, as a succession of earthquakes over the last century have knocked them down!

There are many grand old homes in and around Christchurch that were built in the English pattern, and they are showing quite extensive damage, as their brick walls have collapsed, and in many places roof structures have collapsed, and floors are unsupported. The multiple chimneys have not helped either!

The biggest worry now is the hidden damage: to utilities under the ground like Water mains and Sewers, and to structural elements of buildings. This will be major cost, and will need extensive survey work.

The odd geological feature is the sand volcanos that have "erupted". This is where the ground water and the sand under the area has been liquified by the vibration and been forced up through cracks and fissures as fountains! It all stabilises once the shaking is over, but structures may tilt, and cracks in roads need filling to make them passable. All bridges are closed as a matter of course until they are checked to ensure they are safe and undamaged.

I know there is a lot of misinformation about earthquakes, particularly where they are not experienced. I am very proud of how NZ has become a world leader in earthquake design and construction, (with California and Japan) and is able to save lives in quakes of a size that cause massive loss of life overseas. NZ design innovations have been constructed around the Pacific Rim, and have been proven in earthquakes like Kobe in Japan, and in California.

One idea is Lead-cored rubber bearing pads, which absorb the energy from the ground and protect the building above. (They are replaced after the quake)

I am a local council Engineer, and have a long term interest in this!

Well take care
best wishes from the Shakey Isles!

Rob