At 7.45 am on Monday the 21st of October, 2002, the ground shook. Fifteen minutes later, it shook again – and again, and again. Over the next four weeks, one hundred earthquakes were recorded in the vicinity – and not just as aftershocks. This was an ‘earthquake swarm’, the term given by seismologists to a sequence of earth tremors of varying intensity, clustered in a small area over a short period of time.

One person said: “I heard a big bang and the whole building shook – followed up shortly with another bang and more shaking.” Another claimed: “I could feel the ground shaking below my feet. Desks in the classroom were vibrating as well.”

These reports are not from Japan or California – places renowned for regular earthquake activity – they are from the people of Manchester, England, who were experiencing first-hand what it feels like to be close to the epicentre of an earthquake.

The occurrence of earthquakes in Britain, a country not renowned for earthquake activity, has made some people ask the question: are these faults of Nature – or the fault of Man?

The Manchester quakes measured up to 3.9 on the ‘Richter Scale’. This is an internationally accepted standard of measurement of earthquake activity named after Dr Charles Richter, a US Physicist who developed the scale in 1935. The measurement is ‘logarithmic’, such that each unit of measurement or ‘magnitude’, has an amplitude (height of the wave) ten times greater than the previous one. In terms of energy, each whole number increase corresponds to an increase of 31.6 times the amount of energy released. For example, a 5.0 magnitude earthquake is 31.6 times the energy of a 4.0 magnitude quake, and one thousand times the energy of a 3.0 magnitude event. The highest value on Richter scale is ten.

Other measurements of earthquakes – such as the European Macroseismic scale – describe the amount of surface damage done by an earthquake. On this twelve-point scale, Magnitude 1 can only be felt by scientific instruments, whilst magnitude 12 is ‘Catastrophic’ – almost total destruction. The largest ever recorded earthquake occurred in Chile in 1960. It was measured as magnitude 9.5 on the Richter scale and caused over 5,000 deaths.

The most deaths resulting from an earthquake was reportedly 830,000 following a quake in Shanxi province, China in 1556. The Chinese earthquake has been allocated a magnitude of 8.0 by the British Geological Survey – though how this is possible for an earthquake that occurred 379 years before the scale was invented, only they know!

Seismologists often claim that if they could predict earthquakes ahead of their time, they could save many lives. However, the best methods they have at present are: (a) studying seismic data for patterns associated with earthquakes; and (b) studying how animals react before a quake. Abnormal behaviour of both domesticated and wild animals begins up to 100 days before an earthquake. Wild birds flock together to fly away, whilst caged birds throw themselves against the wire cage. Horses hoof and attempt to escape their stalls, and dogs howl and bark violently. Many animals refuse food. Ten days before the quake, this agitated activity increases rapidly. (It should be noted that such animals do not need to study seismic data).

Around the world there are between eighteen and twenty thousand earthquakes each year of magnitude 2.5 or greater – an average of 50 quakes per day. There are many more of lower magnitudes which can only be detected by seismic instruments. But what is more interesting than the frequency of earthquakes, is what actually causes them to happen.

According to scientists, they are mainly the result of vibrations in the Earth’s outer crust. These vibrations are caused by the slipping of massive underground rocks – particularly ‘tectonic plates’ which border each other at certain locations around the globe. Other earthquakes are caused by volcanic activity, which can trigger earthquakes in an area. But many earthquakes are caused directly by Man, not Nature.

In Denver, Colorado, in 1962, the town began experiencing earthquakes for the first time in its history. Officials finally realised that the quakes started at the same time that the city began pumping waste water into deep man-made wells on the city’s eastern side. As soon as the pumping ceased, so did the earthquakes.

Closer to my home, according to the British Geological Survey, the Manchester and Salford area straddles part of the South Lancashire coalfield. This area had been extensively mined by numerous collieries in the North Manchester city area right up to the late 1970’s. The coals that were removed formed part of a fault block, bounded to the north and east by the Bradford fault. The resulting underground caverns were filled with water or collapsed, causing underground movements in the area, and consequently earthquakes.

Then there is drilling for oil and gas. Norway’s first offshore oil field went into production in 1971; four years later, the UK began extracting oil from the North Sea. Then in 1977 an earthquake of magnitude 5.6, the largest offshore earthquake in British waters in those times, hit the North Sea. Eight years later, in June 1985, another North Sea quake stopped oil production when the affects were felt on the Gorm/Tyra platforms. And more recently, earthquakes are regularly felt in the Norwegian Sea, not far from the Shetland Islands.

But these are a relatively small number of quakes compared to what is happening in Oklahoma, California and Texas in the USA today, where earthquakes have rocketed since 2009. According to scientists, the majority of earthquakes in Oklahoma are caused by the industrial practice known as ‘wastewater disposal’. This is a separate process in which fluid waste from oil and gas production is injected deep underground, far below ground water or drinking water aquifers. The resulting earthquakes often measure between 3.0 and 4.0 on the Richter scale, but have reached magnitude 5 on occasions (September 2016, magnitude 5.8).

There are many other instances where Man has caused earthquakes to occur. It is well-known that dynamite and atomic explosions release large amounts of energy which can bring about a rearrangement of rock in the earth’s crust – in turn triggering earthquakes. Not so many years ago the French, British and others experimented with underground atomic explosions at several pacific islands. It may still be going on secretly today. In my opinion, earthquakes occurring in those areas cannot be divorced from the actions of the experimenters.

We can do little or nothing about those Earthquakes which are a naturally occurring phenomenon. But we can certainly prevent or limit those quakes which are caused by Man’s actions, simply by taking away our dependence on oil and gas and replacing our needs with clean, renewable energy sources.

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