Arya News - Experts say Karachi is surrounded by several active and dormant fault lines, can’t withstand even a moderate intensity tremor.
ISLAMABAD – While the recent seismic activity affecting parts of the city seems to have settled down to an extent, indicating what some experts describe as an “increasing stability” of the reactivated fault line after release of built-up energy, a sense of unease still exists in the people, who repeatedly experienced low-intensity tremors for over three weeks in June, it has emerged.
Speaking to Dawn , the residents of Quaidabad, Landhi and Malir — the localities most affected by a series of low-intensity tremors starting from June 1 and ending on June 22 — say that that the fear of being hit by a potentially a high intensity earthquake constantly grips their hearts.
“We no longer live a normal life. The very thought of being struck by a disaster wakes me several times at night. Last night, too, I felt slight shaking; first at 3am and then at 4.45am. But, there was no official confirmation. I think the tremors were too minor to be recorded,” said Bashir Ahmed Mirjat, local journalist and resident of Umer Marvi Goth, Quaidabad.
According to him, the situation has been extremely disturbing over the last month. On every seismic event, people used to come out on streets, praying for their safety, and then returning to their chores.
“It was a continued state of absolute helplessness. Every day, seemed like the end of life. I can say with certainty that I felt more than 40 tremors — including the first one of 3.6magnitude — in 22 days. Their high frequency badly affected people’s mental health.”
Like Mijrat, who moved to the locality in Karachi three years back, many villagers have had their lives’ first encounter with persistent seismic events. Shocked and panicked, some of them returned to their hometowns.
Faiza Shahzaib, teacher and resident of Landhi, heard a loud and intense sound followed by a tremor just two weeks ago. “It forced all of us to come out on the street. It was the second time that people had to leave their homes out of fear following an earthquake last month. Still, we are too scared.”
Residents believe that their fears stem from the missing role of the state as well as the absence of provision of information by official sources.
Shazia Nadeem, Shahzaib’s colleague residing in the Muslimabad area of Malir City for over five decades, says, “People rely on whatever is being presented on the social media these days, which at times constitute misinformation. Till today, there is no government initiative to inform, educate and train (in disaster preparedness) those living in the quake-vulnerable areas. Hence, most of us don’t know what to do if God forbid, a disaster strikes.”
The residents, from the information gathered from the social media, also link the prolonged seismic activity directly with the excessive withdrawal of groundwater in their localities, which has been facing an acute shortage of piped water for decades. The situation, they believe, is also causing their land to sink.
Sharing data of the city’s low-intensity tremors, Chief Meteorologist Ameer Hyder Leghari, who has done a postgraduate diploma in seismology from Japan, said that the historical data showed that mild to moderate tremors had been recorded in Karachi from time to time since the 1960s.
Life amidst fault lines
Karachi, experts say, is surrounded by several active and dormant fault lines, and the recent seismic events — a total of 57 low-intensity tremors in 22 days in the month of June this year — are consistent with the region’s natural tectonic movements.
“The Landhi, Quaidabad, Gadap and Malir areas are located near active fault lines, making them more to vulnerable to seismic events. Minor earthquakes may pre-empt high-intensity earthquakes by constantly releasing accumulated energy within the Landhi fault,” explains Mr Asif Rana, former director of the Geological Survey of Pakistan.
According to him, the city’s close proximity to several seismic faults, including the Allahbund fault, which runs parallel to Sindh’s coast, and the junction of the Indian, Arabian and Eurasian plates, makes it susceptible to natural seismic activity.
“While the triple junction hasn’t witnessed a major earthquake since 1945, geologists think that substantial seismic energy has been accumulating in the region, making the area increasingly vulnerable to a significant quake,” he said, adding that if such an event occurs under the seabed near Sonmiani, which is only 50km away, it could potentially generate a tsunami that could hit Karachi, too.
Tsunami-generating earthquakes in the region, he says, have been reported as early as 1881. Two offshore earthquakes – one of 8-magnitude reported in 1945 and the other in 1947 of 7.3-magnitude – generated tsunamis, which hit Sindh and Makran coastal areas.
Karachi, Mr Rana points out, is located on the edge of a stable crust of the western rifted margin of the Indo-Pakistan subcontinent, which is creating continuous stress on its rifted western margin, resulting in re-activation of the dormant faults.
“The Landhi fault has become active recently after several decades and is currently going through a normalisation phase. Another nearby fault close to Thano Bulah Khan had also contributed to the last month’s seismic events.”
Asked about the possible link between the recent 5.5-magnitude quake in Musakhel, Balochistan, and Karachi’s seismic events, he said there are no indication that these events are triggering each other as Karachi’s seismic activity is considered localised.
“We must remember, though, that all these events are part of the same regional tectonic framework. This swarm is regarded as normal, not a precursor to a major quake. The region is prone to significant earthquakes, including the devastating 1935 Quetta earthquake of 7.7magnintude, which killed over 35,000 people.”
An analysis of the 57 low-intensity tremors shows the majority (33) were recorded in areas close to Malir. Other areas where tremors were felt were: Quaidabad, Landhi, Gadap, DHA City and DHA Karachi and Korangi. There were 10 tremors on June 2 followed by a dozen the next day.
The last six tremors — four of them had above three-magnitude — were recorded on June 22. “But, what is unusual this time was their high frequency in a single month. Having said that, the city has never seen a major earthquake,” he said.
Both experts endorse the possibility of the city seeing more low-intensity tremors, given the fact that the region is seismically active.
They also call for equipping people in the vulnerable areas with the life-saving knowledge tools required to face a potentially high intensity earthquake as well as ensuring the strict enforcement of building codes.
“It’s time that the authorities take the situation seriously. The haphazard way Karachi has grown over the years is a recipe for disaster as even a moderate intensity tremor (between 4 and 5.5 magnitude) can cause havoc in densely populated areas,” Mr Rana says.
Highlighting the need for continuous monitoring of the fault lines, already known, and mapped, Mr Moin Raza Khan, former head of Pakistan Petroleum Limited, says that tectonic movements definitely disturb the skin of the earth, causing damage to the infrastructure under and above the ground.
“When the earth moves, it readjusts itself and then stays calm. This is called re-equilibration. We need to monitor our fault lines and take steps to keep our infrastructure in and above the ground secured, ensuring the safety of human life and investment,” he says.
‘Sinking’ city
On the link between the extraction of underground water and tremors, senior marine geologist Dr Asif Inam, also the former head of the National Institute of Oceanography, explained that Karachi, like many other coastal cities worldwide, relies heavily on groundwater for both domestic and industrial purposes.
Unregulated withdrawal, he points out, typically leads to the extraction of water beyond the aquifers’ recharge capacity. This often results in the compaction and readjustment of subsurface soil, leading to the subsidence of adjacent land. This land subsidence, he says, can also facilitate faults running parallel to the Karachi’s coastline.
“There is an urgent need to ban unauthorised water withdrawal in Karachi, as coastal areas are already at risk from rising sea levels. Any subsidence in these regions could exacerbate the situation, particularly since the Intergovernmental Panel on Climate Change has predicted a sea level rise of approximately 60 centimetres along Karachi’s coast by the end of the century.”
Dr Inam underscored the need for a comprehensive coastal zone management plan for Karachi to protect strategic infrastructure from the impacts of climate change and related coastal hazards.
“It is essential to continuously monitor changes using modern geodetic techniques, such as InSAR [Interferometric Synthetic Aperture Radar] and GPS [Global Positioning System] measurements, to detect even minor changes in ground elevation that could affect infrastructure or increase flood risk,” he said.