Christchurch - Quake Damage

Rachel and John kindly took us on a tour of central Christchurch.  It was the first time for me to see the town since the two big earthquakes:  the M7.1 Darfield Earthquake on 4-Sep-2010 (link) centered 40km west of Christchurch, and the even more destructive M6.3 on 22-Feb-2011 centered just 10km from the city-center at the very shallow depth of 5km (link).

I remembered central Christchurch as a fairly built-up city with a mix of loverly old stone heritage buildings, several city blocks of large modern office-blocks and hotels, and surrounding of streets of low-rise brick shops.    But the cityscape I remember is now almost entirely gone.

Central Christchurch pre-quake

The symbol of Christchurch was the stone cathedral in the middle of Cathedral Square.  The square was surrounded on all sides by midsize buildings (c. 10 stories) as you can see in the photo above.

Christchurch Cathedral before 2011

In the Feb-2011 earthquake, the Cathedral spire and part of the nave famously collapsed, as did many other masonry heritage buildings.   The unreinforced masonry facades of many of the older shops also collapsed into the streets, which caused many fatalities.

Christchurch Cathedral today 

Of the modern buildings, most survived structurally intact with two notable exceptions:  the 6-story CTV building and the 4-story PGG House which both collapsed, killing 115 and 18 people respectively, out of the total of 185 fatalities.  The CTV building was later found to have an unsafe design which should never have been approved.

Cental-city block : almost entirely demolished

What I hadn't appreciated until I visited the city, was that most of the modern buildings were so badly damaged that they later had to be demolished.   For example, out of Christchurch's 51 tallest buildings pre-quake (10-stories+),  only 11 will be retained and 3 more are still under review.   The remaining 37 have been demolished (see link).

43 of the 51 Christchurch high-rises colour-coded
with their status shown as of May 2013 (link)

The shallow quakes caused violent shaking (MM IX):  "the peak ground acceleration (PGA) in central Christchurch exceeded 1.8g (i.e. 1.8 times the acceleration of gravity), with the highest recording 2.2g (wiki link).   These accelerations are among the strongest recorded worldwide (see PGA link) and exceeded the 'maximum considered event' (MCE) underlying NZs tough building code.     

Cathedral Square from the Gloucester Rd bridge

So when we visited the city center I was shocked to see block after block where almost every building had gone.    The photo above shows Cathedral Square from the Gloucester Road bridge over the Avon - right through what was the heart of the city (from 5 o'clock to 10 o'clock in the photos above).   Vacant lots where I remembered big hotels and office blocks.

Foundations of demolished tower block

Almost all the Christchurch buildings I remembered have gone, with the exception some half-collapsed heritage buildings retained awaiting decisions (and funds) for possible restoration.

Collapsed heritage building and mural

Fortunately one of my favorite heritage buildings, the Arts Center Complex, seems to have mainly survived and be on its way towards restoration.  

Arts Center Restoration

A number of large murals have been installed on the backs or sides of the few buildings that have been retained.  And a few of the vacant lots have been turned into parks.  

Mural and vacant lot from
demolished building

Further out from the city center its a similar story.   Most of the old low-rise unreinforced masonry shops have gone, with just a few left presumably awaiting demolition or reinforcement.

Collapsed facades, demoloshed shops

It was a very depressing picture.  Although it was fascinating, I was also so saddened that I eventually I couldn't bear to see any more.

We had a nice lunch in the tram-way building.   It was good to see the Christchurch Trams is running again.    There was a nice Japanese restaurant, and Rika ordered oysters of course.

Bluff Oysters Japanese style

After lunch Rach and John took us to a temporary shopping mall that had ingeniously been build using shipper containers.  It was actually very pleasant and in the sun, and somehow seemed to retain the Christchurch feeling I remembered.

Temporary shopping mall made with shipping containers

It was impressive to see  the resilience of the Christchurch people.    And in a couple of places we could see new buildings being constructed.  But much less rebuilding than I expected considering it is now 4 years-on.

Hole-in-the-wall

But this got me thinking about the earthquake risk in Tokyo, which is due for a large earthquake (like the 1923 one).  The Japanese are pretty confident in their engineering and tough building standards, so most buildings should avoid collapse.  But what would be the consequences if half or more need to be demolished and replaced?