Preparing for earthquakes By Dr Syed Iqbal Mohsin - Thursday, March 17, 2011

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NO one is more familiar with earthquakes and tsunamis than the Japanese. But the earthquake of March 11 was of such severity that even they were startled.
The buildings swayed to and fro as people hid themselves under heavy furniture for two-and-a-half minutes, which must have seemed like an eternity. When the rocking of buildings stopped they came out on the streets to find them flooded with seawater in the coastal areas. A 10-metre-high tsunami hit the coastal city of Sendai.
Buildings swung less dramatically in Tokyo and Yokohama, which were 230km away from the epicentre of the quake. And there is no verifiable news indicating that any major building collapsed in the wake of the 8.9 magnitude earthquake, or 9.0 to which it has been upgraded, in these areas.
Thoughts go back to the tsunami of Dec 26, 2004 which destroyed life and property in 10 countries killing some 230,000 people. The 7.3 earthquake of Haiti in 2010 caused widespread liquefaction of the soil, causing poorly constructed buildings to go down like ninepins, killing over 200,000 people.
The Kashmir earthquake was no less tragic where a 7.6 magnitude tremor shattered government school buildings on the morning of Oct 8, 2005 killing over 70,000 people. An earthquake in 1923, known as the Great Kanto, caused thousands to die in Tokyo and its surroundings. In contrast, the death toll of March 11 is so far believed to be less than 4,000.
It is axiomatic that earthquakes do not kill; it is buildings that kill. When there is an earthquake of magnitude 7.0 to 7.5 in countries like Pakistan, India, Iran, Turkey, China, Indonesia or Haiti, the deaths are in thousands or hundreds of thousands.
An earthquake demolished scores of newly constructed apartment buildings in the city of Ahmedabad when a 7.5 magnitude quake struck the Indian state of Gujarat on Jan 26, 2001. These were constructed by builders whose sheer motive was profit; little attention was paid to precautions.
‘Run to the bamboo jungle when there is an earthquake’ goes a Japanese proverb. This is the basic concept behind a safe building. The more elastic a building the better its chances of survival when rocked by an earthquake. It may swing like a pendulum along with the seismic waves passing through its foundation but will come back to its original position when the waves have died down.
Among the countries facing the highest level of earthquake hazards are China, Japan, Turkey, Iran — and Pakistan. The Dalbandin earthquake of 7.3 on the Richter scale was only five years after the catastrophic earthquake of 2005 in northern Pakistan. There have been many serious quakes in the country, a few of which we remember. The others we tend to forget.
The 1935 earthquake destroyed half the city of Quetta and the tsunami of 1945 off the Makran coast damaged the Manora lighthouse and was felt as far as Mumbai. Swat was rocked by a 6.5 magnitude earthquake followed by landslides in 1976.
It is customary to divide a region into four earthquake risk zones, four being the highest risk. In Pakistan, Lahore and Peshawar are in zone two, Islamabad and Rawalpindi in zone three, and Quetta and Karachi in zone four. Karachi was also rocked by the 2001 Gujarat quake. However the city escaped destruction whereas Ahmedabad suffered heavy damage.
The quake in Dalbandin in January this year was of magnitude 7.3, but Dalbandin is a small, sleepy town of 15,000 people and the nearest city (Quetta) is 400km away. The earthquake originated from a depth of 64km. Hence the intensity of the quake was reduced by the time it reached the surface.
The most destructive earthquakes are those with a shallow focus. The focus of the Kashmir earthquake was only 26km below the surface. Haiti’s quake had a depth of a mere 13km
The Karachi Building Control Authority, now the Sindh Building Control Authority, contests the US Geological Survey’s placing of Karachi in zone four. According to their building code Karachi is in zone two, a medium-risk zone.
The Geological Survey of Pakistan places the city in zone three on its hazard map. The sub-surface geology of Karachi poses serious questions about its vulnerability. The triple junction of three plates — the Indian, Arabian and Eurasian — is only 40km away. The east-west Allah Band fault passes through the city and a few smaller faults run within the city as well.
There are clusters of apartment buildings in the city which were constructed some 30 years ago. They barely incorporate the safety factors recommended in the Karachi building code. More recent constructions may have included the safety measures of zone two but even they will not survive if there is a shock exceeding 7.0 on the Richter scale and that has its epicentre near the city.
The preparedness for earthquakes begins a few decades prior to an event. In fact, Japan was preparing for the March 11 earthquake for almost 90 years, since the Great Kanto earthquake.
We cannot predict the timing but we know with reasonable certainty that an earthquake of medium severity will occur in Karachi in the coming decades. An extremely strong vibration of the order of 8.5 last year in Chile killed only 400 people. They had suffered a similarly strong earthquake in 1960 and had been preparing for five decades. The same is true for Tokyo and for San Francisco.
Let us not be caught unawares and unprepared. Architects, engineers and builders should follow the building code of the KBCA while building authorities across Pakistan must ensure that builders adhere to earthquake-safety standards to minimise damage in case of a natural disaster.
The write is a geologist and former vice-chancellor of the Federal Urdu University, Karachi and Islamabad.

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