No damage was reported from a magnitude 3.1 earthquake that rattled Salt Spring homes from its epicentre under the sea this week, estimated to originate from a point less than 100 metres off the island’s south-end shoreline.
Light-to-weak shaking was reported to Earthquakes Canada for the 5:30 a.m. quake, which had a calculated depth of just 14 kilometres at a point roughly 1.6 kilometres southwest of Beaver Point Tuesday, Oct. 21. Online reporting, using the Modified Mercalli Intensity (MMI) scale, generally rated the quake MMI III, a “simple rolling” earthquake that tilts sideways along one direction.
Residents of Salt Spring who were awake — or awakened — reported weak shaking, at first confused with now-familiar vibrations from heavy road equipment working outside homes; North and South Pender islanders also reported the quake was heard more than felt, as windows rattled and pictures turned on their shelves. Most reports suggested the event only lasted a few seconds.
Two similar quakes were felt on Salt Spring last fall: a 4 a.m. magnitude 3.8 on Sept. 26, 2024, centred underwater east of Saanichton between Sidney and D’Arcy islands; and a 2 a.m. magnitude 3.5 on Oct. 4, 2024, that time centred beneath the ocean at a rough halfway point on a line drawn between Fernwood Dock and the mouth of the Fraser River.
Tuesday’s earthquake, like those last year, was under the threshold for an early-detection system initiated by the province last year, designed to warn both the public and emergency services managers of quakes greater than 5.0 magnitude, with theoretically as much as 10 seconds of lead time before they hit.