Islanders prudent to seek higher ground: seismologist

  • Jan. 9, 2013 8:00 p.m.

By Alex Rinfret–A magnitude 7.5 earthquake struck off the coast of the Alaska panhandle early Saturday morning (Jan. 5), triggering a tsunami warning that had many islanders scrambling for higher ground. The quake occurred just before 1 am and was felt as far away as Washington State and Edmonton, said seismologist Alison Bird at the Earthquakes Canada office in Sidney. Although only a small wave was recorded, Ms Bird said it’s possible for an earthquake in this region to generate a dangerous tsunami and it’s a good idea to get to higher ground immediately after strong shaking. “I’m glad that people took the initiative and evacuated,” she said. “It was certainly prudent for people to take action.” It was the second tsunami evacuation in less than three months for residents of Haida Gwaii. Saturday’s quake occurred offshore to the north and west of the islands, about 330 km away from where October’s 7.7 earthquake occurred. The latest tremor was along the same fault region, Ms Bird said, and was a “strike-slip” event. A strike-slip is the expected type of quake for this region, she said, adding that October’s earthquake was a more unusual thrust event. Ms Bird said her office has received many reports from islanders who felt the earthquake, with Masset and Port residents reporting particularly strong shaking. No damage was reported, she said, and none was expected as the closest community is 100 km away from the epicentre. Ms Bird said she’s not surprised to hear this quake felt different from October’s, which was closer to Haida Gwaii. Peopleclose to an earthquake occurs feel a sharp, jerky motion because they feel almost all the waves it generates. Further away, people feel only the slower waves, which can travel longer distances than the short waves – the same way that low sounds can be heard further away than high sounds. Many people report that the slower waves leave them feeling nauseous, she said. Earthquakes Canada installed several seismometers here after the October quake and Ms Bird said they are providing valuable information. The equipment made it easier to pinpoint Saturday’s quake, she said, and has also tracked more than 30,000 aftershocks following the October event. The 7.7 Haida Gwaii earthquake was ideal, she said, because it didn’t result in injuries or damage and is providing large amounts of data, helping seismologists understand how a large earthquake would affect more populated areas. Some islanders wondered if the latest tremor would shake things up at Hotspring Island in Gwaii Haanas, where the famed hot springs have run dry since the October quake. But Ms Bird said the monitoring equipment on the island has not detected any changes. She said she’s not surprised, because Saturday’s quake was too far away to undo whatever shifts occurred underground in October.