A magnitude 7.2 earthquake struck waters about 200km west of Sola, Vanuatu, on Saturday, and the Pacific Tsunami Warning Center issued a warning for coastal areas within 300km of the epicentre.
The quake was at a depth of 10km, the United States Geological Survey said, the Daily Mirror reported at 10.46 a.m. Colombo time, citing Reuters. The distance is given as 200km (124 miles) west of Sola, in the Banks Islands of northern Vanuatu.
Hiru News reported at 8.44 a.m. that the Pacific Tsunami Warning Center had issued a tsunami warning following the quake, and that the centre identified a risk of destructive tsunami waves reaching coastal areas within 300km of the epicentre. Hiru attributed the warning to foreign media.
The two filings are complementary rather than overlapping: the Daily Mirror supplies the location, depth and seismological authority, and Hiru supplies the tsunami advisory and its radius. Neither contradicts the other on magnitude.
Depth is the reason for the warning
A magnitude 7.2 does not automatically generate a tsunami. What makes this one a tsunami concern is the combination of shallow depth and an offshore location: a 10km focus under open water displaces the water column above it, where a deep-focus quake of the same magnitude would largely dissipate within the crust. The warning radius of 300km is correspondingly local rather than basin-wide.
The map published with the Hiru report places the epicentre in open water to the north-west of the main Vanuatu chain, with Port Vila marked to the south-east — consistent with the Daily Mirror’s position of 200km west of Sola, and well clear of the capital.
Context
Vanuatu sits on the New Hebrides subduction zone, where the Australian plate descends beneath the Pacific plate. It is one of the most seismically active nations on earth, and the segment west of the Banks Islands produces large offshore events regularly.
There is no reported connection to Sri Lanka, and no Sri Lankan agency advisory has been issued. Sri Lanka lies in the Indian Ocean basin, which is not reached by a Pacific-basin event of this kind.
Not reported
Neither filing reports casualties, damage, or the state of communications with the Banks Islands, nor whether the tsunami warning was subsequently cancelled, downgraded or allowed to expire. Neither gives a wave height observed at any gauge, an evacuation order, or a response from the Vanuatu government or its National Disaster Management Office. Neither reports aftershocks.
Both filings were published within about two hours of each other on Saturday morning Colombo time, early in the event; readers should expect the casualty and damage picture to be filled in by later reporting, and should not read the absence of a casualty figure as a report of no casualties.
Sources: Magnitude 7.2 earthquake strikes waters near Vanuatu — Daily Mirror, October 24, A strong earthquake measuring 7.2 struck near Vanuatu; tsunami warnings issued — Hiru News, October 24 (Sinhala).
