SrinagarThe year 2018 could see a stark uptick in earthquakes, according to a recent report published in Geophysical Research Letters and presented at the annual meeting of the Geological Society of America.
According to Roger Bilham of the University of Colorado in Boulder and Rebecca Bendick of the University of Montana in Missoula, a tiny shift in the speed of the Earths rotation could trigger a doubling of the number of earthquakes the planet experiences.
We have not done anything controversial, Bilham told Kashmir Observer. The numbers of earthquakes that have occurred each year in the past century are well known.
He said the changes in earths rotation rate are also well known. All we have done is to compare these two well known lists of numbers and report an interesting and useful relationship.
The relationship is that the numbers of earthquakes is increased near the time of Earths slowest rotation rate, Bilham said. Thus slow rotation or the Earth does not cause the earthquakes, it merely makes them happen a little sooner than they normally would, adding this is manifest as a small increase in the rate of earthquakes.
We calculate that when the Earth slows, the equator shrinks. Because the tectonic plates cannot shrink so easily, their edges are slightly squeezed together. The amount is tiny, but it adds a little bit more stress to earthquakes that are about to occur, said Bilham.
In the past century this has happened 4-5 times and we are now entering prolonged phase of slowing.
The scientists studied earthquakes above a 7.0 magnitude since 1900. Major earthquakes have been well recorded for more than a century and that gives us a good record to study, Billham told Kashmir Observer.
We have no information on where these earthquakes will occur, except that they will occur at the worlds plate boundaries, when asked whether Kashmir was on the high seismic zone.
The 2005 Kashmir earthquake recorded 7.6 at the Richter Scale had flattened village after village killing at least 86000 people on both sides of the Line of Control.
The earthquake also affected countries in the surrounding region where tremors were felt in Afghanistan, Tajikistan and Chinese Xinjiang. The severity of the damage caused by the earthquake is attributed to severe upthrust.
Kashmir lies in the area of collision of the Eurasian and Indian tectonic plates. The geological activity born out of this collision, also responsible for the birth of the Himalayan mountain range, is the cause of unstable seismicity in the region. The United States Geological Survey (USGS) measured its magnitude as a minimum of 7.6 on the moment magnitude scale, with its epicentre about 19 km (12 mi) northeast of Muzaffarabad, Pakistan-controlled- Kashmir, and 100 km (62 mi) north-northeast of the national capital Islamabad.
In analyzing the data, they found five periods of time where the incidence of earthquakes was higher than other times. In these periods, there were between 25 to 30 intense earthquakes a year, said Bilham.The rest of the time the average figure was around 15 major earthquakes a year. These periods occurred roughly every 32 years.
In their search for correlating factors, they found these periods of higher rates of earthquakes followed a slowing of the earths rotation. They found that there were more large-scale seismic incidents following these five-year intervals of slowed rotations.
It is straightforward, said Bilham. The Earth is offering us a five-year heads-up on future earthquakes. In their official presentation summary, the researchers note it can be between five and six years, and the latest slowdown began in 2011, suggesting that the world has now entered a period of enhanced global seismic productivity with a duration of at least five years.
Knowing that earthquakes will be more plentiful in five or six or seven years is useful because if a city planning department is considering retrofitting buildings to make them earthquake-safe now, or in ten years time, the knowledge that more earthquakes are on their way may make them act now, rather than later, said Billham.
We say nothing about future energy release, he said. We only discuss the number of Richter magnitude 7 and greater earthquakes. We make no distinction between M=7, or 8 or 9. Most of the world’s damaging earthquakes are about M=7 to M=7.5.
We find a statistically meaningful correlation between the length of the day and the numbers of magnitude 7 or greater earthquakes each year in the past 100 years, Billham said. The average number of these earthquakes each year is about 15. In bad years it averages 20. In good years it averages 10. This year we have had only seven (one occurred recently at the Iran-Iraq border). Next year, and probably for the next four years we anticipate it will be closer to the average of 20.
Though it is not clear why the slowed rotation may lead to more earthquakes, Billham and Bendick believe activity in planets core could be involved. Science Mag explained:
When day length changes over decades, Earths magnetic field also develops a temporary ripple. Researchers think slight changes in the flow of the molten iron of the outer core may be responsible for both effects. Just what happens is uncertainperhaps a bit of the molten outer core sticks to the mantle above. That might change the flow of the liquid metal, altering the magnetic field, and transfer enough momentum between the mantle and the core to affect day length.
The researchers findings ultimately only establish correlation, not causation. However, they have stirred up interest. The correlation theyve found is remarkable, and deserves investigation, Peter Molnar, another geologist the University of Colorado, wrote in an article.
They also found most of the massive quakes related to this phenomenon have occurred near the equator.
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