Canterbury Quake – Initial Damage Summary

A state of emergency has been declared in Christchurch city following this morning’s major earthquake. Noisy aftershocks continue. Damage is extensive. Serious power disruption.

Saturday 4th September 2010

A state of Civil Emergency has been declared in Christchurch and in the Selwyn district following assessment of damage caused by this morning’s major earthquake.

The earthquake, now revised to magnitude 7.1 at the much shallower depth of 10 km, struck at 4:35 this morning. The quake was centred 10 km south-east of Darfield, 20 km south-east of Coalgate, 40 km west of Christchurch. The earthquake was not the anticipated Alpine Fault event.

Residents described the quake as a strong rolling motion which lasted for 2 minutes or more, punctuated by sharp jolts. Noisy aftershocks swiftly followed.

Heavy damage is reported from Christchurch, Shirley, Spencerville, Waikuku Beach and Woolston.

Instruments show that a maximum felt intensity of MM9 was reached in suburbs of Christchurch, probably on softer soils. MM8 shaking was recorded in the city of Christchurch and some suburban areas. This type of shaking is described as: “MM 8: Heavily damaging Alarm may approach panic. A few buildings are damaged and some weak buildings are destroyed. ‘

There has been serious disruption of infrastructure with roads and bridges damaged in the greater Christchurch area. Water supplies have been affected and the Rolleston water supply is contaminated. Once power is restored to pumping stations, the damage to water mains will become more apparent. Emergency tanker supplies are being considered.

The sewerage system is seriously compromised with treatment stations offline, and broken main sewers. Sewerage is reported to be flowing from broken main sewers in areas with soft soils. Many residents may need to prepare emergency toilet solutions for use over the next several days.

In Christchurch city building facades have collapsed into streets and some older buildings have partially collapsed. Collapsed brick chimneys have been reported throughout the Canterbury region. Houses have sustained structural damage and damage to household contents is extensive.

Electricity supply is off in much of the area surrounding Christchurch. The national distribution feeds are intact but damage to distribution transformers, some of which have moved, is delaying restoration. A controlled restoration is planned and it is hoped to have power restored to 90% of the greater Christchurch area by nightfall. However, local distribution faults and damaged areas of the CBD will remain shutdown. Houses fed by overhead distribution lines will take longer to reconnect where the earthquake movement has ripped lines down.

The extent of electricity disruption in rural areas is still unclear. Where outages have occurred, restoration is expected to take days.

The telephone network remains intact, with landlines continuing to operate where feeder lines have not been disrupted. The 111 emergency service is operating. 25 sites on Telecom’s mobile network are inoperative and mobile networks are expected to slowly fail as battery supplies become exhausted.

No serious fires have been reported. The strong motion caused by the shallow quake shut down electricity supplies to feeder transformers, when oil level monitors reported alarms during the main earthquake. The tripping of the power supply probably prevented serious electrical fires.

The weather forecast for today is for fine weather. Rain can be expected during the spring season and rooves damaged by collapsed chimneys and damaged structures are of concern.

An earthquake and aftershock report will follow.

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