The 6.3 magnitude earthquake that struck 50 kilometres offshore of Port Alice Friday afternoon had the potential to be more destructive, Natural Resource Canada seismologist John Cassidy said.
The quake was originally said to be a magnitude 6.7 but further data prompted a downgrade to 6.3. “Six point three is considered to be a strong earthquake,” Cassidy said.
The quake was felt across Vancouver Island and the Lower Mainland and as far away as Seattle, Wash.
Estimates about the quake’s duration range from a few seconds to 20 seconds. “The strongest shake only lasted a few seconds but soil conditions and the type of building you’re in will determine how long you feel it for,” Cassidy said. “Places where there are tall buildings and soft soil will feel it longer.”
Although the initial quake is over there will be aftershocks for the next few days. “Some have already happened, the largest one measured 4.9,” Cassidy said.
Earthquakes occur often in the area but are too small to be perceptible. A larger quake usually happens once every 10 years and the area was overdue for one. “It’s not a complete surprise to get one of this magnitude,” he said.
The quake wasn’t more destructive than it was because it occurred offshore and 20 kilometres below the earth’s surface. “If an earthquake that size happened below Port Alberni then there would have been damage,” Cassidy said. “In this case it was far enough away that there was no damage.”
An earthquake in the Forbidden Plateau area in 1946 measured 7.3 and triggered underwater landslides and wave activity and this quake can still trigger the same, Cassidy said.
The quake should be a sobering reminder to people that we live in an earthquake zone. “You should expect a large earthquake at any time and have both a plan and a kit all the time,” Cassidy said.