Another earthquake, another reminder

Dr A Ofori Quaah, Flitwick, Bedfordshire, UK

In seismology, it is said that, “The longer it has been since the last major earthquake, the closer it is to the next one.” So anytime an earthquake occurs anywhere in the world, it is a reminder to any other earthquake prone part of the world that it could be next. In recent weeks, there has been a reminder, a kind of wake-up call, from Japan and then Ecuador.

A former director of the Geological Survey Department of Ghana used to say that, “As Geoscientists, we tend to talk to ourselves.” That is very true because to most outsiders what we have to say as Geoscientists is either gobbledegook or apocalyptic. How do you for instance, explain to a non-geoscientist that Panthalassa could have anything to do with oil discovery in Ghana or anywhere else for that matter?

In 1939, the total population of Accra was 77,000. In the earthquake of 22nd June 1939, twenty-two people died in Accra alone. That is only 0.028 percent of the total population. However, if the figure is then extrapolated to the present population level of two million or thereabouts, the apocalyptic scenarios begin to emerge.

Earthquakes do not kill, it is the structures that human beings construct, often with no thought of its possible consequences on the environment (especially in the developing countries), that kill. Thus if a Magnitude 8.5 earthquake happens in the Sahara Desert, it may be recorded in some parts of the world by the Worldwide Seismometer Network, but it will be no big news anywhere else because there is very little human habitation and virtually no interference with the natural environment over there.

On Saturday, 16th April, Kumamoto, Japan, was struck by a Magnitude 7.0 earthquake. That earthquake was preceded by a Magnitude 6.2 foreshock. The two earthquakes killed 48 people and about 3,000 others were injured. Severe damage occurred in Kumamoto and ?ita Prefectures, with numerous structures collapsing and catching fire. More than 44,000 people have been evacuated from their homes due to the disaster.

On the same day, a magnitude 7.8 earthquake struck Ecuador in South America. The epicentre of the Ecuadoran earthquake was in a sparsely populated part of the country. Yet so far, 587 people have been confirmed dead and the number could rise because over 157 people are still unaccounted for. Another 8,300 have been injured and over 4,000 houses were destroyed by the earthquake, resulting in over 28,000 people living in shelters.

In terms of seismology, there are close similarities between the two earthquakes. The main Japanese shock was of Magnitude 7.0, while the Ecuadoran one was Magnitude 7.8. They were both shallow, 10 kilometres depth for the Japanese earthquake and 19.2 in the case of Ecuadoran earthquake.

Generally, shallow earthquakes tend to cause more damage to civil structures than deeper earthquakes. While the Ecuadoran earthquake was relatively deeper than the Japanese one and of higher magnitude, there was more damage to the built environment and also more fatalities. The reason for the difference is that Japan almost certainly has better building and damage mitigation and prevention procedures than Ecuador.

As was shown on television screens around the world, Japanese emergency agencies were at the scene of the worst hit areas with sophisticated equipment, earth movers, sniffer dogs and infra-red detectors within minutes of the end of the shaking. In Ecuador, rescuers dug with their bare hands, while hand-held megaphones were in use, trying to attract the attention of potential survivors!

Being earthquake-prone, Ecuador probably has a working national building code. The last time we checked at a national conference, there was a plethora of building codes in use in Ghana, depending on where individual Civil Engineers had trained. The attempt to unify and develop a useable national building code did not come to anything. That was about fifteen years ago. I have been away from the scene for more than a decade, but from reports of buildings collapsing out of the blue in various parts of the country, I will be surprised if that programme to develop an enforceable national building code ever came to fruition, and if so whether there is any enforcement of the code.

Disaster management

The process of managing disasters is one area that makes the heart bleed. I was on holiday in Ghana when the Melcom Supermarket Building collapsed without so much as a storm. The saddest part of the incident was the ridiculously childish attempt at managing the disaster. The ABC of disaster management requires that the site of the incident be cordoned off, to enable rescue workers to try and rescue the injured and dying. In the Melcom case, all we kept hearing on the radio as we drove from Tema to Accra was, “Oh, spectators have besieged the place to the extent that the security agents cannot have access to the injured.” As at that point, very senior government, Fire Service and National Disaster Management officials had visited the scene, and some were actually still at the location being photographed, but it did not occur to anyone to draw a cordon around the collapsed structure, to enable the rescue effort to proceed with seriousness.

A similar thing happened after the Accra floods of June 2015, as was shown television screens around the world. Here was a potential crime scene where one would have expected crime officers to move in immediately to prevent forensic evidence from being destroyed. Instead, radio and television reporters and members of the general public were moving freely among the dead, some actually touching the bodies. Eventually, the dead were loaded en masse without so much as polythene to cover their bodies, some of them completely naked, into open tipper trucks! How sad.

Earlier this year, there was a rumpus about fire-fighting and ladders. Some time ago, I witnessed an exercise at the Tema Oil Refinery which included a simulated rescue from one of the higher floors of the main five(?) storey administrative building of the refinery. At that time, the tallest ladder that the Ghana Fire Service could deploy only went up to four floors. From what the Chief Fire Officer reported in the incident referred to above, it did not sound like the Ghana Fire Service has any taller ladders today. Yet sky scrapers, by African standards, are springing up all over Accra, without helipads or helicopters or even ladders for any pretence of fire-fighting.

The past as a key to the present

In the first week of the Ecuadoran earthquake alone there were 700 aftershocks, some of them quite strong. Earthquakes in Ghana are generally followed by long periods of aftershocks. The 1939 earthquake was followed by thirteen months of aftershocks, as many as five or six a day, some as large as Magnitude 4.5. The relatively small Magnitude 4.9 earthquake of 6th March 1997 was followed by twenty-two aftershocks over four weeks. Should a major earthquake occur in southern Ghana tomorrow, how will companies and institutions that occupy high rise buildings cope with having to evacuate three or four times in a working day as a result of aftershocks?

I saw the beginnings of the “Airport City” in Accra, and I cringe each time I have to walk anywhere within that vicinity. Fortunately, these days as soon as I land in Accra, I can vanish to the security and comfort of the Holy Village.

In seismological terms, Ghana is currently experiencing seismic “space” and “time” gaps. In terms of the space gap, the area between Axim in the Western Region and Nyayanu in the Central Region has not experienced any earthquake for more than four hundred years, while the return period of major earthquake in the Nyanyanu-Ho-Akwapim Range Triangle has been quiet for close to ten years beyond its “return” period. All the geological processes that led to major Ghanaian earthquakes in the past are still going on today. And as surely as night follows day, it will happen again. Maybe this is the time we as Geoscientists should begin to talk not only to ourselves, but to society at large.

Stay blessed