27-year-old Rizwan Ahmed tells you with absolute conviction that the reason for the floods and landslides in the hilly areas of Kodagu district this past week was an earthquake reported in the area on July 9. "We felt tremors for about 5-10 seconds on that day and it loosened the soil. It is because of that the landslides have been so severe this time around," he says, sitting at the relief camp in Kottamudi in the district.
A resident of Eradane Mannangiri, around 25 km from Madikeri in the district, Rizwan and his family were rescued from their village by volunteer groups from Madenadu, a nearby village.
Rizwan is not alone in believing that the earthquake last month played a part in the floods and landslides that ravaged parts of Kodagu. Many survivors across the district believe that the tremors were the reason for severe landslides that swept houses, electric poles and trees away in its path.
However, a team of seismologists from the National Geophysical Institute of India (NGRI), who arrived in Madikeri this week to check if tremors added to the destruction in the hilly areas of the district, believe otherwise.
"Earthquakes can trigger landslides, but it usually immediately follows the earthquake. In this case, an earthquake was recorded on July 9 but we cannot link it to the landslides that occurred last week," says Vijay Raghavan, senior scientist at NGRI in Hyderabad.
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Hattihole in Kodagu district after landslides in the area
The team of seismologists headed by Vijay installed a seismograph at the Jawahar Navodaya Vidyalaya in Hebbettageri and checked if there was any activity.
The team could only confirm a 3.4 magnitude earthquake recorded on July 9, around 25 km north-west of Kodagu. This appears to coincide with some of the severe landslides that occurred in the district in Jodupala, Mannangiri and Chermane, where the National Disaster Response Force (NDRF) was involved in an operation to rescue stranded residents. The tremors then were also felt in Mukkodlu, Thanthipala and Hattihole, where the Dogra and MEG officers of the Indian army were spearheading rescue operations in the past week.
Vijay Raghavan and his colleagues from the NGRI have installed more than hundred seismic stations in the country. "The landslides have occurred due to the prolonged high-intensity rainfall in the region in the last two months," Vijay adds.
Officials at the National Centre for Seismology (NCS), an office attached to the Ministry of Earth Sciences of the Central government, too confirmed that it was unlikely that earthquakes triggered landslides in the region.
"It is highly unlikely that the 3.4 magnitude earthquake triggered landslides in the region, which took place several days after the earthquake. In the Sahyadri mountains (or Western Ghats) there are a few regions where earthquakes are frequent (e.g., the Koyna region in Maharashtra), but so far none of them has reported having triggered landslides during or immediately after the earthquake," read a statement from Vineet Kumar Gahalaut, scientist and Director, NCS.
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Landslide in Mukkodlu, around 25 km from Madikeri in Kodagu
The group contended that the reason for the severe landslides in Kodagu was linked to the heavy rainfall experienced in the region over the last two months. “The rainfall seen in Kodagu was already high in July and the soil in the region was saturated. After a fresh burst of heavy rainfall in the region from August, the landslides occurred," says Sunil Gavaskar, a meteorologist at the KSNDMC.
According to data compiled by the organisation, parts of Kodagu district received more than 200 mm of rainfall on three consecutive days – 15, 16 and 17 August.
"The soil was already moist and this spell of rain in August was classified as very heavy rainfall. This factor coupled with the heavy deforestation on the slopes of the hills in Kodagu led to the severe landslides," adds Sunil.
However, scientists are still trying to understand why exactly the landslides occurred in the region.