Hyderabad:Prakasam district experienced six seismic events on Monday, marking the third consecutive day of tremors. According to the National Geophysical Research Institute (NGRI), the first quake, with a magnitude of 0.9, occurred at 3.51 am and was recorded 12 km southwest of Addanki. The second event, registering a magnitude of 1.8, was recorded at 10.24 am, approximately 12 km west of Addanki.
The NGRI later recorded four more tremors in the same area of magnitudes 1.4, 1.3, 0.8 and 0.7 at around 8.15 pm.
The recent seismic activity in the area began on Saturday morning with a 3.1-magnitude earthquake recorded 12 km west of Addanki. On Sunday evening, a 2.1-magnitude quake was reported 9 km southwest of Addanki.
“This is part of what is known as an earthquake swarm,” explained Dr V. Raghavan, chief scientist at NGRI. “A series of earthquakes occur within a short period in a localised area. This phenomenon is not new.”
He said similar swarms had been observed in Borabanda and Vanasthalipuram in Hyderabad, and in Nellore over the past decade. One contributing factor was the movement of the Indo-Eurasian tectonic plate, which shifts northeastward at a rate of 5 centimetres per year.
Additionally, the Gundlakamma fault, which covers the Prakasam district, is particularly prone to low-magnitude earthquakes, Dr Raghavan added.
Dr Raghavan noted that such earthquakes could sometimes be very shallow and localised, occasionally accompanied by atmospheric sounds resembling cannon shots. The accuracy of seismic event recording depends on factors such as the quake’s depth, magnitude, and proximity to a recording station.
“More recording stations are essential to accurately detect earthquakes below a magnitude of 1. Currently, NGRI operates 12 recording stations across Andhra Pradesh and Telangana, enabling us to reliably record quakes above magnitude 1,” he stated.
The ongoing seismic events point towards the need for expanded monitoring networks to better understand and respond to such localised tremors.
According to Dr N. Purnachandra Rao, former director of National Council of Examiners for Engineering and Surveying and former chief scientist at NGRI, Prakasam district's unique geo-tectonic features made it prone to earthquakes.
“The Eastern Ghats take a sudden turn here. The intersection with major river basins (Gundlakamma, Krishna and Musi) also makes it a seismically weak zone. This region can experience earthquake swarms, where epicentres are distributed circularly. Typically quakes occur along the fault-lines.”
“The fault system here supports such distribution. Proximity to a water reservoir might also play a role, though no extensive studies have been conducted,” Dr Purnachandra explained.
He added that being part of the Indo-Eurasian plate, Andhra Pradesh and Telangana experience intra-plate disturbances, where the plate's movement creates inward forces. These quakes, however, are unlikely to exceed a magnitude of 5, reducing the risk of major calamities.
