Christchurch - 2010
Christchurch, New Zealand is located on the Pacific ‘ring of fire’ makes it vulnerable to tectonic hazards. It is much less vulnerable than for example Haiti because it has sophisticated monitoring, wealth and a small population of only 4.4 million. An earthquake struck on 4th September 2010 and was similar in magnitude to the Haitian earthquake in January 2010 (magnitude 7.0) measuring 7.1 on the Richter scale. In New Zealand there were no deaths and only 2 serious injuries in comparison with Haiti which suffered 300,000 casualties and 1.3 million displaced people. In comparison the disruption in New Zealand was quickly dealt with.
On February 22nd a 6.1 magnitude aftershock hit Christchurch on the South Island, New Zealand’s second largest city. This killed 181 people and damaged the city severely. It was the second most deadly disaster in New Zealand’s history and the estimated cost of rebuilding is around NZ$15 billion making it the country’s most expensive.
The cause of the earthquake was the boundary where the pacific plate converges with the Indo-Australian plate subduction – responsible for the volcanic activity on the North Island where the major earthquakes are located. Magnitude 5 earthquakes occur on average once every 10 years. The south Island experiences less large earthquakes and the September earthquake was the largest recorded for the Canterbury region. The plate boundary has resulted in the major Alpine and Hope fault lines, movement, strike-slip faulting and smaller faults cause the South island quakes.
The 2011 quake (aftershock) was cause by movement along a previously unknown fault running roughly east-west to the southwest of Christchurch. The relatively shallow depth of 5km of the earthquake resulted in its destructive power being high even though its magnitude was not particularly high. The epicentre was also much closer to Christchurch at 10km south west in port Hills. It was likely an aftershock although still remains debatable amongst geologists due to it having occurred on a separate fault than the 2010 quake.
The distance from the epicentre and geology compounded the destruction caused. The hard volcanic rocks of the Port Hills resulted in seismic energy being reflected back up to the surface. In addition liquefaction was caused as ground water levels were close to the surface (previously had been areas of lakes) causing further damage to infrastructure and buildings.
The country is well prepared to deal with tectonic hazards as a rich nation and previous history. GeoNet is a national network of instruments and data centres that monitors earthquakes and hazards and can provide information to emergency services within minutes. GeoNet is funded by the earthquake commission set up by the government to provide insurance to homeowners and education on ‘quake-safeing’ their homes. There are building codes (implemented as early as 1935 and updated today) protect buildings from damage during moderate earthquakes and in the case of major ones ensuring they do not collapse. Older building have to be enforced although only in the North island – this was not seen as essential in the south Island making Christchurch’s heritage buildings much more vulnerable.
New Zealand’s preparedness was not able to prevent the consequences of the earthquake for many reasons. The shallow focus and close proximity to the epicentre meant the effects were measured as 8 on the Mercalli intensity scale (measures building destruction). Many buildings had already been weakned by the September earthquake. The city was crowded at the time as it struck on Tuesday (weekday) at 12:51pm.
Almost half of the buildings in Christchurch were damaged or destroyed as the peak acceleration was 1.8 times higher due to gravity. The six storey Canterbury television centre collapsed, killing 85 people. Christchurch’s tallest building a 26 story hotel was displaced 0.5m and had to be demolished, more than 100,000 homes were damaged or destroyed and 100 more damaged beyond repair by an aftershock in June 2011.
Liquefaction was widespread in Christchurch and always posed a risk due to the city being underlain with soft sediments but was exacerbated in 2011 with the unseasonably high water content of the sub-strata. Many schools that were undamaged by the quake had to close due to liquefaction from the bursting of stressed pipes. The AMI stadium had deep foundations and a network of 10m stone pillars covering 12,000m square to reduce the risk of liquefaction, however this was not enough as 2 stands subsided around 40cm.
The port Hills area suffered considerable slope failure as previously vertical cliffs remnant of sea cliffs experienced rock and debris falls causing fatalities and building damage at the base.
Following the earthquake the government established the Canterbury Earthquake Recovery Authority with the estimated cost of recovery at $13 billion. The city was divided into 4 zones depending on the severity of damage.
The red zone was the residential area along the banks of the river Avon. The area suffered considerable lateral spreading as a result of liquefaction. The government agreed to buy over 5,000 of the worst affected insured properties which can not be repaired for over 3 years.
The orange zone there are 10,000 homes which have to be investigated before anything can be done on them.
The government immediately activated its National Crisis Management Centre, and declared a national state of emergency the day after the quake. Christchurch’s central business district remained cordoned off for more than a month after the earthquake. Electricity was restored to 75% of the city within three days, but water supplies and sewerage systems took a number of weeks to restore in areas affected by liquefaction.
In the weeks following the earthquake about 70,000 people were believed to have left the city due to uninhabitable homes, lack of basic services and continuing aftershocks. Timaru’s population swelled by 20% and thousands of pupils registered at schools in other cities and towns. However, many were expected to return to Christchurch as conditions improved.
The Great Hanshin earthquake, or Kobe earthquake, occurred on Tuesday, January 17, 1995, at 05:46 JST, in the southern part of Hyōgo Prefecture, Japan. It measured 6.8 on the moment magnitude scale (USGS). The tremors lasted for approximately 20 seconds. The focus of the earthquake was located 16 km beneath its epicenter, on the northern end of Awaji Island, 20 km away from the city of Kobe.
Approximately 6,434 people lost their lives (final estimate as of December 22, 2005); about 4,600 of them were from Kobe. Among major cities, Kobe, with its population of 1.5 million, was the closest to the epicenter and hit by the strongest tremors. It caused approximately $100 billion in damage, 2.5% of Japan's GDP at the time. Note: After this earthquake, seismic intensity observation in Japan was fully mechanized (from April 1996).
The Mag 7.2 earthquake struck at 05:46 JST on the morning of January 17, 1995. It lasted for 20 seconds. During this time the south side of the Nojima Fault moved 1.5m to the right and 1.2 meters downwards. This was because the earthquake's focus was so near the surface and its epicenter so near to Kobe.
The effects can be divided into primary and secondary effects. Primary effects included the ruin of 150,000 buildings, the collapse of 1 km of the Hanshin Expressway, the destruction of 120 of the 150 quays in the port of Kobe, and fires which raged over large portions of the city. Secondary effects included disruption of the electricity supply. Residents were afraid to return home because of aftershocks that lasted several days (74 of which were strong enough to be felt). The majority of deaths, over 4,000, occurred in cities and the suburbs in Hyōgo Prefecture.
One in five of the buildings in the worst-hit area were completely destroyed (or rendered uninhabitable). About 22% of the offices in the central business district were rendered unusable, and over half of the houses in that area were deemed unfit to live in. High rise buildings that were built after the modern 1981 building code suffered little; however, those that were not constructed to these standards suffered serious structural damage. Most of the older traditional houses had heavy tiled roofs which weighed around 2 tons, intended to resist the frequent typhoons that plagued Kobe, but they were only held up by a light wood support frame. When the wood supports gave way, the roof crushed the unreinforced walls and floors. Newer homes have reinforced walls and lighter roofs to avoid this, but are more susceptible to typhoons.
The extent of the damage was much greater than in the similar-magnitude Northridge earthquake in Los Angeles, which occurred exactly one year earlier. The difference was in part due to the type of ground beneath Kobe and the construction of its buildings (e.g. many unreinforced masonry buildings collapsed). The immediate population bases of the two areas (Kobe area and San Fernando Valley of Los Angeles) were roughly the same – about 2 million; however, only 72 people died in the Northridge quake, compared to the more than 6,000 in Kobe.
Transportation infrastructure damage: the collapsed elevated Hanshin Expressway made front pages of newspapers worldwide. Most people in Japan believed those structures to be relatively safe from earthquake damage by design. Though the initial belief was construction had been negligent, it was later shown that most of the collapsed structures were constructed properly to the building codes in force in the 1960s. However, the 1960s regulations had already been discovered to be inadequate and revised several times, the latest revision in 1981, which proved effective but only applied to new structures.
Ten spans of the Hanshin Expressway Route 43 in three locations in Kobe and Nishinomiya were knocked over, blocking a link that carried forty percent of Osaka-Kobe road traffic. The Meishin Expressway was only lightly damaged, but was closed during the day until February 17, 1995 so that emergency vehicles could easily access the hardest-hit areas to the west
Artificial islands, such as the modern Rokkō Island and Port Island, in Kobe suffered some subsidence due to liquefaction of the soil; the water breaking to the surface did not come from the sea. However, the newly completed artificial island supporting Kansai International Airport was not significantly affected, due to being further away from the epicenter and because it was built to the latest standards.
In the aftermath, both citizens and specialists lost faith in the technology of their early warning systems and earthquake construction techniques. The national government of Japan led by Prime Minister Tomiichi Murayama was criticised for not acting quickly enough to save many people, for poorly managing Japanese volunteers, and for initially refusing help from foreign nations, including the United States, South Korea, Mongolia, and the United Kingdom. The language barriers and the obvious lack of Japanese medical licensing by foreign volunteers were cited as justification. In response to the widespread devastation, the Japanese government increased its spending on earthquake-resistant building structures.
Local hospitals struggled to keep up with demand for medical treatment, largely due to collapsed or obstructed roads that kept supplies and personnel from reaching the affected areas. People were forced to wait in corridors due to the overcrowding and lack of space. Some people had to be operated on in waiting rooms and corridors.
To help speed the recovery effort, the government closed most of the Hanshin Expressway network to private vehicles from 6:00 am to 8:00 pm daily and limited traffic to buses, taxis and other designated vehicles.
The earthquake caused approximately $102.5 billion in damage. Most of the losses were uninsured, as only 3% of property in the Kobe area was covered by earthquake insurance, compared to 16% in Tokyo. The quake ravaged many of the facilities of what was then the world's sixth-largest container port and the source of nearly 40% of Kobe's industrial output.
The earthquake proved to be a major wake-up call for Japanese disaster prevention authorities. Japan installed rubber blocks under bridges to absorb the shock and rebuilt buildings further apart to prevent them from ‘falling like dominoes’. The national government changed its disaster response policies in the wake of the earthquake, and its response to the 2004 Chūetsu earthquake was significantly faster and more effective. The Ground Self-Defense Forces were given automatic authority to respond to earthquakes over a certain magnitude, which allowed them to deploy to the Niigata region within minutes. Control over fire response was likewise handed over from local fire departments to a central command base in Tokyo and Kyoto.
In response to the widespread damage to transportation infrastructure, and the resulting effect on emergency response times in the disaster area, the Ministry of Land, Infrastructure and Transport began designating special disaster prevention routes and reinforcing the roads and surrounding buildings so as to keep them as intact as possible in the event of another earthquake.
LEDC
Chengdu China - 2008
On the 12th May 2008 a 7.2 magnitude struck 90km north of Chengdu pop. 3.9 million in Sichuan province South East China. Sichuan province is mainly rural and the death toll was nearly 70,000 1 month after the quake. China doesn’t lie on any tectonic plate boundaries however; the earthquake was caused by stress build up between the movements of the Tibetan Plateau and the converging with the underlying crust of the Sichuan basin. Thus is related to the Northwards movement of the India plate against the European plate of 50mm/year responsible for the Asian highlands and the eastwards movement of the crustal material.
There was extreme shaking in a North eastern direction from the epicentre near in Qingchuan county subsidence and street cracks were obsereved in some cities and 1.5km of faulting was observed. On May 25th there was an aftershock which measured 5.4 killing 8, injuring 927, and destroying 40,000 homes.
Although the area experiences earthquakes it was not prepared for such a strong magnitude earthquake, which was felt as far away as Taiwan, Thailand and Bangladesh. 70,000 people were killed and 350,000 injured. The earthquake affected over 45 million people in 10 different provinces. 5 million building collapsed and 21 million damaged in Sichuan. Towns including Beichuan and Wuolong were completely destroyed. The total economic cost was $86 billion. Rescuers struggled to gain access to the areas affected because of the rural locations, mountainous terrain and landslides which had blocked some roads. Landslides had created 34 barrier lakes (with combined rainfall) threatened 770,000 people downstream. More than 2,000 dams fractured resulting in rescue operations had to divert to containing the threat.
The earthquake was unpredicted and Sichuan was an area that has been largely untouched by Chinas economic rise. There was not a sufficient earthquake regulations till after 1976 Tangshan earthquake and building regulations are hard to enforce in the rural countryside.
80,000 troops were sent by the government to Sichuan and some had to be parachuted due to the rough terrain. Secondary hazards began to arise due to dam failure lakes such as the Tangliashan were diverted into the quake effected town of Beichuan. 55 billion yen was raised by both domestic and foreign nations and 95 million had been allocated by the government to the rescue operation.
