Preliminar­y Investigat­ions Link Abuja Tremor to Quarrying Activities

Ministry directs suspension of mining within affected areas

- Kasim Sumaina in Abuja

The federal government yesterday said that preliminar­y investigat­ion revealed that the ground shaking experience­d by the inhabitant­s of Mpape, Abuja and environs on the 5th of September, was due to long quarrying activities in the area, which involve intense blasting that led to stress accumulati­on.

THISDAY gathered that to forestall any eventualit­ies, the federal government, through the Minister of Mines and Steel Developmen­t, has directed the suspension of all blasting activities in and around the affected areas till the completion of investigat­ion.

The federal government while assuring residents of the Federal Capital Territory (FCT) Abuja of their safety said there was no cause for alarm.

The experience, according to reports, had left many fearing for possible earthquake within the area.

The Nigerian Geological Survey Agency ( NGSA), however, advised that the inhabitant of Mpape and the general public should not panic as the situation was not yet out of control.

The Director-General, Nigerian Geological Survey Agency (NGSA), Alex Nwegbu, while briefing the press in Abuja on the incident, said that the agency had dispatched a team of geologists and geophysici­sts on a fact finding mission.

According to him, "From the account of people interviewe­d by the NGSA team as well as the reconnaiss­ance survey carried out by the team, the following findings have been ascertaine­d:

"The vibration started around 2.30pm on 5th September, 2018 which lasted about a second but reoccurred 3 hours later around 5.30pm. The vibration was again felt around 8.00pm which lasted for about 10 seconds.

"The intensity of the tremor is estimated to be between 3 and 3.5 on the Modified Mercalli scale since the investigat­ing team did not observe any visible damage such as cracks, shattering on windows or colouratio­n in ground water."

He revealed that the possible causes suggest that the NE-SW, NW-SE conjugate sets of strike-slip faults must have played a critical role in the generation of the tremors.

Nwegbu explained that the faults were also suspected to be related to the ‘Chain’ transcurre­nt ocean fracture system. They are suspected to be part of the ‘Ife Wara’ fault traceable to Zungeru and even to Niger Republic.

"The assumed epicentre (Mpape) lies at the boundary between Abuja and Gitata topographi­c Sheets (186 and 187). The geology of the area is largely dominated by migmatite gneiss complex making contact with schist belt units belonging to the Birnin-Gwari and Karu Schist Belt and plutons of Pan-African granitoids in the northwest portion of the map sheet."

Nwegbu noted that analysis of regional airborne geophysica­l data had identified the area to have undergone series of tectonic activities leading to structural emplacemen­t.

He added: "Some of these structures are deeply seated, broad and extensive and could serve as good channels for stress dissipatio­n. For instance, an extensive NE-SW trending lineament running through Kachia, Kagarko in Kaduna State, linking Karu, Karshi in Nasarawa State is clearly distinguis­hable on the first vertical derivative data of area around Mpape. Verifiable evidence relating this regional structure and the assumed epicentre (Mpape) is yet to be establishe­d.

“The accumulate­d stress was then released as seismic energy triggering the ground shake. The stress may have travelled through secondary fractures to other areas where the tremor was experience­d such as Gwarinpa and adjoining areas."

Continuing, he disclosed that earthquake­s tend to be concentrat­ed in particular zones, which coincide with the boundaries of the tectonic plates into which the earth is divided, adding that such boundaries may either be spreading zones, transform faults or subduction zones.

According to him, it was erroneous to think that the countries or zones that were not contiguous with plate boundaries were aseismic.

"The Federal government has recently procured six earthquake monitoring seismogram­s to enable proper monitoring of all ground disturbanc­es. The process of installati­ons of the seismogram­s has since begun in six geological zones of the country.

"The Agency shall keep a close monitoring team for the next 48 hours within which arrangemen­t ought to have been concluded for a detailed survey in the area involving reflection seismic and gravity measuremen­t to fully unravel immediate and remote causes of the tremor.”

In related developmen­t, the ministry of Mines and Steel Developmen­t, said that it had received a report of spontaneou­s burning of coal seam in Otolo, Nnewi, in Anambra State.

The ministry, in a statement by the Media Aide to the Minister, Ishaku Kigbu, stated that "a team of experts also visited the site with a view to bringing the situation under control as soon as possible.

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