SCROTOCTUS t1_j8odkgq wrote on February 15, 2023 at 8:07 PM

Reply to comment by PhuckSJWs in Was Western Washington’s infrastructure the reason the Nisqually quake had no direct fatalities? by yungcarwashy

The 9.0+ where it's like the whole region gets stuck inside a Shake Weight is not going to be a good time.

iamlucky13 t1_j8prghz wrote on February 16, 2023 at 1:50 AM

Because of the distance of the Cascadia Subduction Zone from Seattle, the local shaking will be more comparable to a magnitude 7 quake directly beneath Seattle. The biggest concerns for this quake scenario are the regional scale of the effects, and especially the dangers on the coast of the tsunami that will likely accompany it.

Here are the USGS predicted intensity maps showing this, as well as the 2001 Nisqually quake and the 2023 Turkey quake for comparison:

Magnitude 9.3 Cascadia Subduction Zone - Predicted - Modified Mercalli Intensity in Seattle 7 to 7.5

Magnitude 7.2 Seattle Fault Zone - Predicted - Modified Mercalli Intensity in Seattle 8 to 8.5

Magnitude 6.8 2001 Nisqually Quake - Modified Mercalli Intensity in Olympia: 6.5 to 6.8

Magnitude 7.8 Turkey 2003 Quake - Modified Mercalli Intensity: Over 9 in the worst affected areas

With that said, construction methods and quality matter a lot. The shaking in the Gaziantep, where a historically significant castle received major damage that has been shown widely in the news, the Mercalli Intensity is estimated at 6.7 - similar to what Olympia experienced in 2001.