1,108 tremors have rocked Gujarat since the Big One

AHMEDABAD: The cracks formed in many a building in Gujarat on January 26, 2001, continue to widen even after nearly two years, thanks to the aftershocks.
Though occupants of such buildings may not be able to feel the tremors, the terra firma under Gujarat has not ceased rocking since the quake, even if its intensity and frequency are diminishing.
Seismographs installed by the Indian Meteorological Department at Bhuj, Surat, Ahmedabad, Rajkot and Bhavnagar have recorded as many as 1,108 tremors of magnitude three or above on the Richter scale, since the earthquake.
"The aftershocks continue even now.Two days ago an aftershock measuring 3.8 on the Richter scale was registered. But the frequency and magnitude of aftershocks has reduced considerably," says RK Bakliwal director of the India Meteorological Department (IMD), Ahmedabad.
Data on aftershocks gathered by the IMD reflects this trend. The figures show that on June 30, 2001, there were 787 aftershocks of intensity The total had reached 953 by December 31, 2001. In June 2002 it reached to 1,046 and till January 21, 2003 it stands at 1,108.
An aftershock of magnitude 5.8 on the Richter scale was recorded on January 28, 2001, two days after the quake. Quakes measuring three or less on the Richter scale are usually not felt by humans but recorded by the machines.
Those upto 4.9 magnitude on the Richter scale are considered ''slight'' and those above are considered ''moderate''.
However, the epicentre of most aftershocks has remained around the same place, as that of the earthquake. "No new epicentres have developed," says Bakliwal.
The continuing tremors have taken their toll — widening cracks on walls and near door and window frames. A large number of apartment dwellers and even those living in houses have witnessed re-appearance of small cracks either in repaired or fresh areas.
Jagdishbhai Parekh, who lives in Thakorebaug Flats in Navrangpura area, complains, "We repaired and plastered the area with cracks after the quake. However, cracks have started resurfacing."
A similar observation occupants of flats from different areas of the city.
Contradictory claims had been made by different scientists immediately after the earthquake on the possibility of recurrence of large number and high intensity aftershocks.
However, former director of the National Geophysical Research Institute (NGRI) Hyderabad, Dr Vinod Gaur, had warned on January 26 that such a major earthquake was liable to cause a large number of aftershocks and some of them could have an intensity of over five on the Richter scale.
Several scientists had said that after the primary earthquake takes place to release the strain developed along any fault line, the release of energy ordinarily takes place as a one-time event.
But aftershocks in such a situation are caused due to the release of strains caused by the shock waves, which are generated by the primary quake. The number, intensities and timings of the aftershocks follow a statistical pattern and the number of occurrences of such aftershocks would bear a logarithmic relation with time.
This would mean that on an average, the number and intensity of the aftershocks would be going down and the time period between two aftershocks would gradually increase.