by Scott Schaefer
The recent and tragic news reverberating from last Friday’s devastating earthquake and tsunami in Japan has caused a lot of concern for people living in the northwest, who wonder what might happen if a major quake and wave were to strike here.
Several scientists have been working to assess tsunami hazards within Puget Sound communities, including Burien, to provide information for planning and mitigation based on a 7.0+ tremor on the Seattle Fault, which runs from Dyes Inlet on the west through downtown Seattle and through Lake Washington. Two scientists who’ve published a website study are Shun-ichi Koshimura and Harold Mofjeld (read it here: http://nctr.pmel.noaa.gov/pugetsound/pre2).
According to their website, 1100 years ago it is believed that a tsunami was caused by a large quake on that fault (this was an inner-Puget Sound wave and not one that traveled through the ocean).
“According to the recent seismological studies, the Seattle Fault is believed to be a zone of thrust or reverse faults that strikes through Seattle in the densely populated Puget Lowland of western Washington,” reads a statement on the study’s website. “The structure of the Seattle Fault zone still have great uncertainty and there exist a number of interpretations.”
Scientists have created video simulations of what a tsunami created by a 7.0+ magnitude quake on the Seattle Fault might do, and their models are based on a 1998 sonar mapping project of Puget Sound (we remember the ships off Burien’s beaches, and the low, deep occasional rumbling of their testing). Then, in 2000, they recorded the demolition of the Kingdome with seismic recorders. Put together, they “inferred that the length of the Seattle Fault is at least 70 km and the fault could produce a M=7.2 to 7.5 earthquake for a fault length of 70 km and fault plane depths between 20 to 30 km.”
While the tsunami simulations are cool, it’s hard to determine exactly the size range of waves that might hit, and what kind of damage it’d cause, but we think that this is better than nothing.
Here’s one video simulation that we took the liberty to enlarge, in order to see what effect a Seattle Fault earthquake tsunami might do to our shorelines:
Here’s a more enlarged version, showing how the brunt of the (simulated) wave would hit Seahurst Park Beach and the north side of Three Tree Point, then seemingly wash over most of the point as it heads towards Tacoma; then a second wave might hit the south side of the point:
And here’s one NOAA made that shows the possible effects on Seattle:
And here’s a video we hadn’t seen yet, taken from a Coast Guard helicopter as the Japanese tsunami hit Crescent City, CA:
And news footage of the wave hitting Santa Cruz, CA:
So, are YOU prepared to make it through a huge quake and the impact of a local tsunami? Please Comment below…
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by Scott Schaefer
Thank you so very much for thee blog……I read it every other day or oftener. It is newsy and very well written. I appreciate it. We live in Gregory Heights.
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