Certain parts of Idukki district that houses a string of hydro-electric dams and reservoirs, including the State's largest, experienced a series of tremors through Tuesday afternoon.
According to sources in India Meteorological Department (IMD), the first quake was measured at 3.5 on the Richter scale.
The National Disaster Management Authority in New Delhi also confirmed the magnitude was 3.5, and dismissed measurements of up to 4 put out earlier on the day by different agencies.
EPICENTRE
The Centre for Earth Science Studies based here located the epicentre at 3.7 km north of Vellikulam between Moolamattam (where the power station of Idukki dam is situated) and the emerging hill tourist destination Vagamon.
A tremor of magnitude 2.9 reported during last November had also originated very near the same location. Reports from the CESS station in Idukki said no major damage was reported.
The tremor that lasted more than two seconds was felt near the Idukki dam, Velliyamattam, Udumbannoor, Ilapally, Pianav, Cheruthoni, Vagamon, Upputhara and Kumily.
ACROSS CLUSTERS
The Amateur Seismic Centre based in Wellington in New Zealand and formerly in Pune, India, says seismic activity in the recent past has occurred in clusters along the border with Tamil Nadu, primarily in the districts of Idukki and Palakkad.
A number of faults have been identified in the State of Kerala out of which a few, such as the Periyar Fault, are active, the centre says.
But this is not to suggest that proximity to faults does necessarily translate into a higher hazard as compared to areas located further away.
This is since damage from earthquakes depends on numerous factors such as subsurface geology as well as adherence to the building codes, it says.