Anxiety as earth tremors persist in Abuja, Saki, others

•Researchers predict 40% possibility of magnitude 7.1 earthquake in Nigeria by 2028, seek better understanding of active regional tectonics

Episodes of earth tremors in Abuja and environs, Niger, Kaduna, Kwara, Saki in Oyo, and Ile Ife in Osun have left tell-tale signs of a re-occurrence.

The Guardian reliably gathered that an unreported seismic activity in early November 2021 have received attention of the National Assembly and the Presidency.

Indeed, Abuja has in recent past become a home of tremors. The last officially reported episode was on November 1, 2018. An earlier event on September 5, 2018 that lasted for three days in Mpape and some parts of Maitama district in Federal Capital Territory (FCT) left not only residents, but also the whole country apprehensive that an earthquake was about to occur.

Residents of Abuja, Saki in Oyo, Ife in Osun who confirmed the incidents said the tremors lasted for days. “It didn’t look good. The whole place was shaking,” Jimoh Abba told The Guardian on Monday.

The Guardian reliably gathered that the Federal Government might soon raise an emergency committee to tackle regular tremors in Nigeria.

Scientists at the National Space Research and Development Agency (NASRDA) and sources at the National Assembly confirmed the earth tremors to The Guardian.

It was reliably gathered that the Senate Committee on Science and Technology is already seeking remedial measures and assurances before making the announcement to Nigerians.

Also, researchers from Department of Civil Engineering, Covenant University, Ota, Ogun State, have predicted the possibility of earthquake of magnitude of 7.1 in Nigeria by 2028.

The study titled “Probabilistic Seismic Hazard Analysis of Nigeria: The Extent of Future Devastating Earthquake” was published in journal IOP Conf. Series: Materials Science and Engineering.

The researchers concluded: “The findings of this assessment established that Nigeria is at the risk of experiencing devastating earthquakes in the future. These Probable earthquake magnitudes are as high as 6.0 in the year 2020; 6.5 between the year 2021 and 2022; 7.0 between the year 2025 and 2026 and 7.1 in the year 2028. The probability that these events will take place in the forecasted year is 36.79 per cent. The probability that an
Earthquake of magnitude 7.1 will also occur from 2019 to 2028 is between nine per cent and 36.79 per cent.

“It is therefore recommended that the Nigerian authority begins to enforce the law as regards earthquake considerations in structural designs in places such as the South-West region that has displayed most seismic events in times past. It is also recommended that activities such as heavy rock blasting should be relocated to non-residential places to reduce earthquake stimulations in residential areas.”

According to Earthquake Magnitude Scale, 5.5 to 6.0 magnitudes will cause slight damage to buildings and other structures; 6.1 to 6.9 may cause a lot of damage in very populated areas; 7.0 to 7.9 magnitudes is major earthquake with serious damage; and 8.0 or greater magnitude is great earthquake and can totally destroy communities near the epicenter.

According to studies, earthquakes occur due to the sudden release of built-up energy within the rocks. Other activities carried out on land surface can also stimulate earthquake. Some of these activities include drilling of boreholes and erection of heavy buildings.

Simply put, an earth tremor is a sudden shaking of the ground that causes destruction, as a result of movements within the earth’s crust or volcanic action. It is of a smaller magnitude compared to an earthquake. Tremors and quakes are measured with a seismograph.

An earthquake, on the other hand, refers to the violent shaking of the earth surface, resulting from the sudden release of energy in the Earth’s lithosphere that creates seismic waves.

Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to toss people around and destroy whole cities.

A large earthquake from afar will feel like a gentle bump followed several seconds later by stronger rolling shaking that may feel like sharp shaking for a little while.

A small earthquake nearby will feel like a small sharp jolt followed by a few stronger sharp shakes that pass quickly.

A recent study published in September 2021 edition of the journals Frontiers in Earth Science and Advances in African Earth Sciences and titled “On the Origin of Orphan Tremors and Interpolate Seismicity in Western Africa” confirmed the occurrence of tremors in Nigeria.

The researchers concluded: “We investigated the source of ground shaking reported during September 5–7, 2018, in the Abuja area, central Nigeria. We reviewed previous seismic activity in the region, speculated on how the shaking is related to unique teleseismic events, or may be connected to other alternative explanations, that is, anthropogenically triggered, or whether regional tectonics and local geology could have made the region more susceptible to triggered fault rupture and amplification of seismic shaking. We explored the spatial and temporal origins of the shaking using seismology and studied the basement structure and surface deformation using aeromagnetic and SAR data. We found the strongest support for seismicity related to anthropogenic groundwater extraction. While other hypotheses cannot be ruled out completely for the case study presented here, we point out that more work is needed to establish a better understanding of the potential connections between inherited basement structure, active regional tectonics, and anthropogenic stress perturbations.”

The researchers are from the Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY, United States; Department of Geosciences, Virginia Tech, Blacksburg, VA, United States; Goergen Institute for Data Science, University of Rochester, Rochester, NY, United States; Department of Geology, Obafemi Awolowo University (OAU), Ife, Osun State, Nigeria; and School of Geology and Geophysics, University of Oklahoma, Norman, OK, United States.

MEANWHILE, NASRDA had in 2018 warned that Nigeria should be prepared for earthquake experience, which should set the authorities thinking and planning now.

The predicted date of 20 years from 2008 of an earthquake occurrence in Nigeria is not far, as signs have started emerging through the Abuja earth tremor.

Although, the Emergency Management Agency of Nigeria’s Federal capital territory, Abuja, confirmed the reports of the earth tremor in the affected areas, it suggested it could have come from the movement of the earth or that it could be by the blasting of rocks or mining in the area, while it urged residents to stay calm and hide under tables if inside the house or stay away from buildings if outdoor.

The NASRDA had told journalists that it has established that the November 1, 2018 earth tremor in some parts of Abuja was a weak event and not strong to cause any damage to structures.

The Space Agency maintained that aftershocks from a main event might continue to occur in days, weeks and even in months depending on the nature of the fault.

The Space Agency revealed that findings from earlier investigations by its Centre for Geodesy and Geodynamics in Toro has shown that small magnitude earth tremors of less than or equal to 3.5 have high probability of occurrence in Nigeria in future.

He, however, said there is need for seismic and other relevant monitoring equipment in all areas where earth tremors have been witnessed for effective monitoring of seismic activities.

In a recent publication in a learned journal, the scientist said: “At exactly 3:10 GMT on September 11, 2009, an earth tremor occurred in the Abeokuta environs, Ogun State. This earthquake was felt mainly in most parts of Ogun State and some parts of Lagos State. Three seismic stations of the Centre for Geodynamics and Geodesy (CGG) network in Nigeria, recorded this event. Since 2008 when CGG network started, September 11 event was the first major tremor recorded instrumentally. Although there have been many earth tremors (minor to major) in the past in this part of the country and other areas but there have not been local instrumental records to analyse the seismicity (vulnerability to earthquakes) of the region.”

The NARSDA researchers said the tremor is a sign that Nigeria is not immune from earthquake occurrence. One of the researchers from the Geology Department of Obafemi Awolowo University (OAU), Ile Ife, Osun State, Dr. Abraham Adekunle Adepetumi had told The Guardian that the country is not in the earthquake-safe region.

Predicting long-term earthquake possibility for the Southwest, he said: “The Empirical Earthquake Recurrence Model – a time-dependent model – was employed to predict the probabilistic occurrences of earthquakes in the Ijebu-Ode and environs between the year 2008 and 2028.

“This probability model takes the mean recurrence intervals and standard deviation of historic earthquake events in this area to determine the probability of earthquakes occurrence for the predicted years.”