Mizoram’s zone of “scary” earthquakes is caught between two subterranean faults, a geologist assigned to make a preliminary study on the frequent tremors said.
The State’s Champhai district and adjoining areas could experience aftershocks for several months but the people there have nothing to worry if their magnitude does not measure above 5 on the Richter scale, he assured.
Mizoram experienced at least eight moderate earthquakes between June 21 and July 9. The tremors ranged from 4.2 to 5.5 on the Richter scale.
The epicentre of most of these quakes was beneath Champhai district bordering Myanmar, including the last one of magnitude 4.3 and about 10 kilometres deep. A few were beneath the adjoining Saitual and Serchhip districts.
“Earthquakes have happened and will happen in that part of Mizoram because it is caught between two geological faults. These are the Churachandpur Mao Fault and the Mat Fault,” said Dr. Saitluanga who teaches geology at the Pachhunga University College in State capital Aizawl.
Faults are discontinuities or cracks that are the result of differential motion within the earth’s crust. Vertical or lateral slippage of the crust along the faults causes an earthquake.
The Churachandpur Mao Fault is named after two places in Manipur and runs north-south into Myanmar along the border of Champhai. The Mat Fault runs northwest-southeast across Mizoram, beneath river Mat near Serchhip.
“There are several shallower transverse or minor faults in between these two major faults that are deeper. We have reason to believe the earthquakes have been caused by these minor faults,” Dr Saitluanga told The Hindu .
The tremors after the strongest of these earthquakes on June 22 have been aftershocks that can happen for a long time, he said.
“But as long they are below the intensity of 5, there’s nothing to worry. Quakes are happening all the time, most of them not felt by us, which is good because the release of energy in small amounts can prevent the build-up of a large earthquake,” he added.
An aftershock of 5 or more on the Richter could be a sign of a major earthquake waiting to happen, he said.
CM’s calls for study
On July 10, Mizoram Chief Minister Zoramthanga wrote to the Centre seeking assistance and sanctioning of an extensive study by seismologists or geophysicists on why the frequent earthquakes were happening.
He also sought installation of earthquake observation centres in the eastern part of the State with “real time seismic telemetry for earthquake disaster preparedness”.
According to Champhai’s Deputy Commissioner Maria C.T. Zuali, much destruction was done by the earthquake of intensity 5.5 on June 22. “The quakes have damaged 158 houses, churches and community halls,” she said.