Earthquake: When Quetta trembled
An earthquake is the trembling of the ground caused by a sudden release of energy accumulated in the rocks beneath the earth’s surface for millions of years. An earthquake can take place any time, anywhere in the world and thousands occur each year. Some are strong enough to wreck entire cities while most are so mild that they can hardly be felt.
One of the most severe earthquakes and subsequent tsunami, measuring 9.1 on the Richter scale, was the one that jolted Japan on March 11, 2011. Some other powerful earthquakes that pummelled the earth in the last century include the 8.25 magnitude earthquake in California, 1906, 7.7 magnitude in Nevada, 1915, 8.5 magnitude in Yokohama, Japan, 1923 and the earthquake in Chile in 1960 which racked up an 8.5-magnitude. For Pakistan, the earthquake that devastated the city of Muzaffarabad in October 2005 with a magnitude of 7.6 is perhaps the most memorable but it was not the first earthquake to bring misery to our country.
Seventy seven years ago, at around 3.00am on the morning of May 31, 1935, the city of Quetta was jolted by an earthquake measuring 7.6 on the Richter scale. The shocks were felt about 165km to the southwest of Quetta. It was the deadliest earthquake in the history of Balochistan killing about 70,000 people and injuring and displacing many more.
The focus (the point within the earth where seismic waves originated) of the earthquake was 12km deep in the earth and its epicentre (the point on the earth’s surface directly above the focus) was recorded about 16km in the Chiltan mountains west of Quetta. The duration of the earthquake was 10-20 seconds. Shallow depth of focus and proximity of the epicentre to populated areas caused thousand deaths and large scale damage to infrastructure in Quetta and its surrounding area.
The buildings in and around the city could not withstand the earthquake and were reduced to rubble leaving Quetta in ruins.
Many were buried under the rubble and later pulled out by rescue workers. After the Quetta earthquake the British Government formed building codes and rules to be followed for future construction in Quetta and the surrounding areas.
But none of these codes have been put into practice for the past several decades.
Experts have determined that various areas of Pakistan lie along fault lines, i.e. fractures in rocks where the possibility of earthquakes is high. The zone between Quetta and Kalat is one of the active fault zones in Balochistan. The Chamman fault, extending from Kharan, Pakistan to Kabul, Afghanistan — a distance of about 850 to 900km — is capable of generating earthquakes of various magnitudes.
The Geological Survey of Pakistan (GSP) organised a symposium on “Seismo-tectonics and seismic hazards in Pakistan” on March 24, 2007 at Islamabad. Several research papers concerning the science of earthquakes were presented to create awareness among the masses. Though the science of seismology helps us understand earthquakes better than we did decades ago, there is still no sure fire way to predict an earthquake.
No one can stop an earthquake from taking place. But the loss of life and property due to earthquakes can be reduced to a large extent if building codes and rules are followed during the construction of buildings and infrastructure.
The importance of building codes can be judged by the Chilean (South America) earthquakes of 1960 and 2010. When an 8.5 magnitude earthquake and subsequent tsunami hit Chile in 1960 it resulted in great damage to life and property.
Following this disaster, the Chilean government put strict building codes in place to prevent a tragedy of such magnitude from happening again; thus, when in 2010 Chile was hit by an even more severe earthquake of 8.8 magnitudes, there was far less destruction. This was all because the Chileans followed the building codes and rules while constructing buildings. Had people in Pakistan followed the 1935 building codes the number of dead and injured would have been much lower in the earthquake that hit Khyber Pakhtunkhwa and Azad Kashmir in October, 2005.