7 Comments
Nov 4Liked by Judith A Hubbard

I very much appreciate the quality of your reports. You’re very detailed and informative. But I am raising my arm in the back of the lecture hall and objecting to the statement that this event “…is in no way related to the Cascadia Subduction Zone…” The transform fault structure in which it occurred exists to release energy resulting from movement of two subducting plates in Cascadia, the Gorda and Juan de Fuca plates. Wouldn’t it be more accurate to describe the rupture as unrelated to subduction down dip from the subduction boundary?

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author

Hi John, of course you are correct that there is a relationship between the two different plate boundaries - and therefore, in some sense, a relationship between earthquakes on the two plate boundaries. As you point out, the driving force causing slip on the transform is associated with slab pull at the subduction zone.

What I was hoping to communicate was that this earthquake did not occur on the subduction zone, and did not affect the risk profile of the subduction zone. I could have been more precise in my phrasing.

Thanks as always for your engagement and for keeping us honest!

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Off subject: new subject: was that Mw=6.2 event off Chile in the plate before the trench, or the subducting portion? I can’t tell the geometry from the USGS info. It seems large for an inter plate event. On the plate contact with the mantle? But that would be unusual.

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Never mind. I read your article. More complicated than I imagined. Thanks.

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Oct 31Liked by Judith A Hubbard

Very interesting post. For figure 3, what time period does this record of earthquakes cover? Is it since 1980 same as Figure 5?

Thanks.

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author

Thanks for asking! The image on the left (Cascadia) shows earthquakes from the USGS catalog, starting around 1900 CE. The image on the right (South America) shows earthquakes from a variety of sources, including some large historical events prior to 1900.

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Oct 31Liked by Judith A Hubbard

Thanks for another interesting report! I always learn new things from your postings. You both have such a broad base of knowledge to even have the 1700 quake is your article AND the associated reports of early settlers and the Japanese tsunami.

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