Hi Petra. There is some evidence that the answer to your question is out there. A shock, which reached a maximum intensity of VII at a number of places in the Puget Sound area was felt over about 182,000 square km, occurred on February 14, 1946. A few deaths were attributed indirectly to the shock; damage was estimated at $250,000, mostly in Seattle. Most of the reported damage was limited to cracked plaster and slight chimney failure, but there were a few cases of spectacular building damage in Seattle. The magnitude 5 3/4 tremor was also felt in southwestern British Columbia and northwestern Oregon.

One of the strongest earthquakes on record for the Puget Sound area followed a few months later. A magnitude 7.3 shock in the Strait of Georgia on June 23, 1946, caused the bottom of Deep Bay to sink between 2.7 and 25.6 meters. These measurements were reported by the Canadian Hydrographic Department. Also, a 3 meter ground shift occurred on Read Island. One person was drowned when a small boat was overturned by waves created by a nearby landslide. Waves were reported sweeping in from the sea, flooding fields and highways. Heavy damage occurred in the epicentral region. South of the Washington State boundary, some chimneys fell at Eastsound and on Orcas Island and a concrete mill was damaged at Port Angeles. Some damage occurred on upper floors of tall buildings in Seattle. The shock was strongly felt at Bellingham, Olympia, Raymond, and Tacoma. The total affected area in Canada and the United States was about 260,000 square km.

Property damage estimated at upwards of $25 million resulted from a magnitude 7.0 earthquake near Olympia on April 13, 1949. Eight deaths were caused either directly or indirectly, and many were injured. At Olympia, nearly all large buildings were damaged, and water and gas mains were broken. Heavy property damage was caused by falling parapet walls, toppled chimneys, and cracked walls (MM VIII). Electric and telegraphic services were interrupted. Railroad service into Olympia was suspended for several days; railroad bridges south of Tacoma were thrown out of line, delaying traffic for several hours. A large portion of a sandy spit jutting into Puget Sound north of Olympia disappeared during the earthquake. Near Tacoma, a tremendous rockslide involving an 0.8 km section of a 90 meter cliff toppled into Puget Sound. The felt area extended eastward to western Montana and southward to Cape Blanco, Oregon, covering about 400,000 square km in the United States. A large portion of western Canada also experienced the shock.

I can’t say that these quakes were on subduction faults as I have not been able to locate the coordinates for them. If I could I would be able to run a catalog check of the surrounding area and see if there were a series of quakes before these larger ones. Take Care…Don in creepy town.