Of the 20 aftershocks, the ISR has categorised two tremors recorded on Monday of 4.6 and 4.1 magnitudes as separate earthquakes, because they occurred in different faultlines, the official said.
As many as 18 aftershocks and two quakes have been experienced in Gujarat’s Kutch district in three days since the earthquake of 5.3 magnitude rattled parts of the state on Sunday, an official from the Institute of Seismological Research (ISR) said on Tuesday. Of the 20 aftershocks, the ISR has categorised two tremors recorded on Monday of 4.6 and 4.1 magnitudes as separate earthquakes, because they occurred in different faultlines, the official said.
An aftershock of 3.7 magnitude was recorded at 10.49 am on Tuesday, while three other aftershocks — of magnitudes 2.3, 1.7 and 1.9 — were recorded on Monday night, he said. Of 19 tremors recorded till Tuesday morning, two are new earthquakes with 4.6 and 4.1 magnitudes that had occurred on separate branches of the main south Waghad faultline on Monday, said Sumer Chopra, director of Gandhinagar-based ISR.
“Not all of these tremors are aftershocks of the Sunday’s quake. Some of them are from nearby fault lines as well,” he said. The 5.3-magnitude earthquake occurred on south Wagad fault, which is a system of faults with many branches. When a moderate intensity quake occurs, it disturbs the nearby branches, Chopra said.
“So, when this moderate intensity shock occurred, it disturbed nearby connected faults and passed on the energy to them,” he said. The quakes with intensities of 4.6 and 4.1 magnitude that occurred on Monday were on the branches of the main south Waghad fault, and were technically separate earthquakes, the official said. According to the ISR, an earthquake of 4.6 magnitude occurred at 12.57 pm on Monday with its epicentre 15 km north-northeast from Bhachau in Kutch and this was followed by a quake of 4.1 magnitude at 3.56 pm at six km north-northwest of Bhachau.
The combined aftershocks of these three earthquakes stand at 17 so far, the official said. The 5.3 magnitude earthquake recorded at 8.13 pm Sunday night shook Kutch and parts of Gujarat including Rajkot and Patan. According to the Kutch district administration, no casualties or major damage to properties were reported in any of these earthquakes. Kutch district is located in a “very high risk” seismic zone, and earthquakes of lower intensity occur regularly there.