THE VARYING DAMAGE OF THE CHRISTCHURCH EARTHQUAKES

THE VARYING DAMAGE OF THE CHRISTCHURCH EARTHQUAKES

Damage from the Canterbury earthquakes varied greatly from region to region of Christchurch. One street may have been completely destroyed, while another in close proximity was untouched. The reason for this variance is multifaceted. Different soil types react differently to seismic activity, and each area has differing styles of buildings. This means that areas with older buildings may have had more earthquake damage. Land near waterways vulnerable Much of Christchurch city and its immediate neighbouring settlements are situated on river deposits, beach dune sand, estuaries, lagoons and swamplands that have been drained over time. Before the construction of stopbanks and river realignment in the mid 19th century, the Waimakariri River […]

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TYPES OF BUILDING DAMAGE

TYPES OF BUILDING DAMAGE

Building damage can be divided into two broad categories: damage that was caused solely by earthquake shaking; and damage that resulted from ground deformation including liquefaction, lateral spreading or landslip. While shaking damage to dwellings has been observed on the flat, the February and June 2011 aftershocks in particular caused significant shaking damage to hillside houses. The observed high vertical accelerations were responsible for severe damage sustained by tile roofs and brick veneers, and unreinforced foundations were often severely cracked. Liquefaction effects on buildings Liquefaction-induced ground movement has caused stretching, hogging, dishing, racking/twisting, tilt, differential settlement, differential displacement or any combination of the above to buildings. The severity of the […]

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LIQUEFACTION – WHAT IS IT

LIQUEFACTION – WHAT IS IT

Liquefaction is a process where by firm ground takes on a liquid form temporarily. This generally happens during seismic events such as earthquakes. A notable example of this was during the Canterbury earthquakes of September 2010 and February 2011. In these events liquefaction caused silt and fine sand to ‘boil’ up and cause widespread damage. Entire streets were buried with this silt and sand, swallowing vehicles and buildings alike. Causes of liquefaction Over the course of thousands of years, rivers and streams deposit layers of silt and sand. Low-lying areas such as swampland and peaty marsh have higher concentrations of this silt and sand. Coastal areas also generally have higher […]

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