KARACHI: OVER the past few months, those living close to the sea in Karachi — especially in Defence and Clifton — have experienced several tremors, though mostly of a minor nature. Following the massive earthquake of October 8, the city has been jolted at least twice. The first one happened a couple of weeks ago and was felt at around half past midnight. The second tremor was felt on the evening of October 23 half an hour before Iftar.

The next day the chief of the Pakistan Meteorology Department was quoted as saying that what the city’s residents had felt was not related to any seismic activity. So the question then arises what was it? Those who felt the tremor heard a sound and it felt as if the walls were shaking. It lasted only a couple of seconds.

The inability of the government or any of its agencies to explain to the public the reasons for these tremors has led to much speculation. The most common rumour circulating these days is that the tremors may be caused by offshore drilling off the coast of Karachi in the Arabian Sea by some multinational oil companies. However, this seems unfounded if a closer look is taken at the seismicity (the seismic profile, so to speak) of the region where Karachi is situated.

First, an image search on the Internet search engine Google will reveal that Karachi lies very close to a major fault line, where the Indian tectonic plate meets the Arabian tectonic plate. According to seismologists, up to 95 per cent of all recorded earthquakes have taken place along fault lines, where two or more tectonic plates meet.

For an even closer look at lower Sindh’s seismicity, one can take a look at the website of the India-based Amateur Seismic Centre (http://asc-india.org) which has extensive details on the earthquake history of South Asia. For instance, while Karachi lies close to a major fault line, it is situated on or close to four minor faults. The first is called the Allah Bund fault and it passes through the coastal town of Shah Bundar, the area around Pakistan Steel Mills and runs through eastern parts of the city ending near Cape Monz. Another fault lies in the Rann of Kutch near Sindh’s southeastern border with India. The third is called the Pubb fault which lies near the Mekran coast west of the city while a fourth is located in Dadu district on the northern boundary of Karachi.

According to the website, which quotes from extensive scientific and historical sources (all cited), a massive earthquake measuring 7.5 hit Debal east of present day Karachi in the Indus Delta in either 893 or 894 AD. Up to 150,000 people were believed to have died and the temblor resulted in the Indus River changing its course westward. To the north of Debal, near present-day Hyderabad, the towns of Bahmanadad and Mansura were badly affected. They were important cities in the region and suddenly disappeared from the historical record. Archeological excavations at the sites reveal “human bones, which were found in doorways, as if people were attempting to escape, or in the corners of rooms, some upright, some recumbent, with their faces down and some crouched in a sitting posture” as quoted by A. Cunningham in his “The Ancient Geography of India” (Delhi, 1871).

On May 2, 1668, a quake measuring 7.6 hit the Sindh coastal village of Shah Bundar destroying it.

On June 16, 1819, a quake measuring 7.5 on the Richter scale hit parts of western India and present-day Sindh. Its epicentre was 185 miles east-southeast of Karachi in the Rann of Kutch. Over 1,500 were believed to have died in the quake. The earthquake resulted in the raising by 4.3 metres of an approximately 90-kilometre long stretch of land. A representative of the British governor at Bhuj said that the shaking lasted nearly two minutes. A tributary flowing into the Indus was also thought to have dried up as a result and the tremor was strongly felt in Hyderabad, Sindh. Aftershocks to this quake went on for several months but gradually decreased in magnitude.

More than 4,000 people were killed on the Mekran coast by an earthquake and a tsunami that followed it in 1945. The quake occurred on Nov. 28 and its epicentre was 98.5 kilometres southeast of Gwadar or 408 kilometres west of Karachi. In Karachi, the quake was felt for 30 seconds. Lighthouses at Cape Monze and Manora were both damaged and the shockwave was felt as far east as Kanpur. Tsunamis generated by the quake reached heights of 40 feet in some Mekran ports and caused great damage including wiping out the fishing village of Khudi, 30 miles west of Karachi. At Karachi, the waves were recorded at a height of 6.5 feet and came in intervals, with the first coming at 5.30am, then at 7 am, 7.15 am and finally at 8.15 am. Luckily there was no damage to the boats at the port or to any of its installations. A tsumani close to seven feet high was recorded at Mumbai and 15 people were washed away there.

Even the Gujarat earthquake of 2001 which killed thousands in India was strongly felt in Karachi and Hyderabad (where a seven- storey building collapsed), the former being a mere 235 miles from the quake’s epicentre.

It should be clear that Karachi lies in a zone with some degree of seismic activity. In fact, the Geological Survey of Pakistan’s national seismic hazard map places the entire Sindh coastline including Karachi in a zone of “noticeable seismic danger”. It has also placed a detailed note on its website saying that the Oct. 8 quake has made it “mandatory” to update the existing National Seismic Hazard Map.

The questions that need to be answered, especially with the recent earthquake activity in and around the Karachi region, are: (1) Does the Oct. 8 earthquake in any way affect the tectonic plate movement for the rest of the country, especially Karachi, since it lies close to a faultline? (2) Does the more recent seismic activity in the southern and coastal areas of Sindh mean that tectonic activity is increasing and, if so, should not this be a valid cause of concern given the way thousands of high-rise buildings are constructed in Karachi, often without any regard for construction rules? (3) If the national seismic hazard map needs to be updated, will Karachi be moved from its present category of “noticeable seismic danger” to that of “significant seismic danger”?