‘Exhaustive studies needed for Palghar quakes’
Gahalaut said, “Yes, it is unusual in the sense that this activity is continuing for so long. Earlier, we had several such earthquake sequences elsewhere in central India which started with or immediately after monsoon and then stopped after the monsoon or after some time of monsoon."
PUNE: Frequent tremors and earthquakes in Palghar district since November 2018 has become a cause of concern not only for the residents but also for the civic administration. However, Vineet Gahalaut, Director of National Centre for Seismology, which falls under the Ministry of Earth Sciences, feels that it needs to be studied well, before reaching any conclusion.
While talking exclusively to Sakal Times from Delhi, Gahalaut said, “Yes, it is unusual in the sense that this activity is continuing for so long. Earlier, we had several such earthquake sequences elsewhere in central India which started with or immediately after monsoon and then stopped after the monsoon or after some time of monsoon. In this case, the activity started much after the monsoon and is continuing even now.
Adding that incidents occur due to local activity, he explained, “The central India experiences such activity and many of them are linked with the monsoon. But then there are a few, probably including this one, which are not related to monsoon. Such sequences or swarms occur because of local crustal adjustment in the region in response to the internal deformation of the plate.
Apparently, Palghar district, located in northern Maharastra, was in a panic on February 1, 2019, after a series of minor earthquakes rocked the region. There were as many as six tremors in a day, ranging between 3 and 4.1 on the Richter scale.
NCS has established three temporary stations to observe and record the seismic activity at Dhundalwadi, Dongripada and Talasari. Explaining the concept Swarm, Gahalaut said, “Swarm is a sequence of earthquakes in which (1) all earthquakes have almost a similar magnitude, (2) all of them are of generally low magnitude and (3) the earthquakes are clustered in time and space. In such a sequence, no large magnitude occurs. Such activity is common where fluids (e.g. rainfall) are involved.”
When asked that similar Swarm activity was noticed before the Koyna (1967) and Latur (1993) earthquakes, he said, “We did not have good recordings of the events before the Latur and Koyna earthquakes. Thus, it is difficult to say whether the foreshock sequence (if any) before the Latur and Koyna earthquake was similar to the ongoing sequence at Talsari, Palghar.
“From the earthquake magnitudes, their pattern of occurrence, both in time and space, it appears that it is a swarm activity and it is very ‘unlikely’ that it can lead to a large magnitude earthquake. This is based on our limited understanding of earthquake occurrence processes and the experience of swarm activity in the central India region. I may add here that the earthquake occurrence processes are more complex, non-linear and least understood and hence, there could be surprises,” Gahalaut said.
Underlining the need to be vigilant during such activities, he added, “Buildings of a large congregation may be assessed from the earthquake safety point of view, the weakened structures may be identified and if possible, can be retrofitted. It is important that people follow the building code of BIS for new construction and also for retrofitting.”
“There have been several cases of swarm activity in the Jawhar region (50 km from Talsari, Palghar), Amravati region, Khandwa region, etc,” he said.