5.6 Mw - QUEEN CHARLOTTE ISLANDS REGION

Magnitude	5.6 Mw
Date-Time	12 Dec 2007 23:39:59 UTC 12 Dec 2007 15:39:59 PST
Location	52.277N 131.348W
Depth	10 km
Distances	236 km (147 miles) SSW (198 degrees) of Prince Rupert, BC, Canada 317 km (197 miles) S (177 degrees) of Metlakatla, AK 320 km (199 miles) NW (305 degrees) of Port Hardy, BC, Canada 666 km (414 miles) WNW (303 degrees) of Vancouver, British Columbia, Canada

This event was caused by north-northwestward motion of the Pacific plate past the North American plate along the Queen Charlotte Islands fault zone. The Queen Charlotte fault is a transform fault between the North American and Pacific plates. It is similar to the San Andreas Fault in length and both are transform boundaries between different parts of the Pacific and North American plates. The Queen Charlotte Fault gets much less attention because it is offshore and only affects a few cities with significant populations.

Map showing earthquake epicenter (yellow star) and motion vectors (blue) for the Juan de Fuca and Pacific Plates with respect to the North American plate.

Seismograms

The event was clearly detected by the AS-1 stations in the U.S. Below are two examples from Oregon.

College Hill, Corvallis, (CHOR) Helicorder Record

CHOR Extracted record with P pick. (Low pass filtered with corner at 8 s.)

CHOR Travel-time graph.

Lincoln School, Corvallis, Corvallis, (LSOR) Helicorder Record.

Note room noise due to classroom activity.

LSOR Extracted event. (Low pass filtered with corner at 8 s.)

LSOR Travel-time graph.

Bob Butler’s station at the University of Portland, Oregon.