Talk:Cascadia subduction zone

Another Interpretation?

What is with this section? It is both extremely technical and unsourced except the cite to Lyatsky at the top of it. Is the whole section the "summary"? What is quoted and what is not needs to be clearer, and it would help to make, at the least, the purpose of this section of the entry make more sense to the layperson.

24.21.86.235 09:48, 16 May 2007 (UTC)

Assessment

After reviewing this article, it is no longer a B class article and has been downgraded. The reviewed version contained more information, but much gas been removed as I guess OR. To get back to B class this needs a proper WP:LEAD; some information on the volcanoes, not just a list (aren't they supposed to be formed from the lava that is created buy the subduction of the ocean plate or something?); a better description of location in the geography section that should mention the US and Canada for those less familiar with the region. As a bounus, in-line citations would be a great addition, and I believe are now required to reach GA. Aboutmovies (talk) 06:41, 21 February 2008 (UTC)

Yes, downgrade was proper. This article's coverage of the topic is incomplete and uneven, and really needs reorganization by someone with some grasp of the topic. - J. Johnson (JJ) (talk) 18:14, 11 August 2010 (UTC)

Question.

How do i do to translate this article to Spanish? —Preceding unsigned comment added by 190.208.74.141 (talk) 19:53, 6 March 2010 (UTC)

"Great Earthquakes" chart

I copied a chart of past Cascadian subduction earthquakes from the 1700 Cascadia earthquake article, and reformatted it a little. It's not well sourced there, however; a newly-added citation ("Cascadian Megaquake 4 of 5". BBC. Retrieved 2011-03-15.) has a lot of good information. On the other hand, it's a BBC show, but not on the BBC site, and looks like it was uploaded without proper authorization; the citation could go away if the BBC objects.

Anyway, one of the scientists in the BBC citation points out three layers of evidence for past earthquakes: "about 600 BC", "about AD 400", "about AD 700". That seems to cover, more or less, the table's 600 BCE, 400 CE, and 810 CE quakes, and the program in general is all about the 1700 quake. But that segment (part four of five) doesn't mention 170 BCE or 1310 CE quakes. While it's a really good program (shaky upload permission issues aside), it's not so good as backing for the table.

Great Earthquakes

est. year	interval (years)
F 1700 CE	390
E 1310 CE	500
D 810 CE	410
C 400 CE	570
B 170 BCE	430
A 600 BCE	unknown

I'm duplicating the chart at right, to save it in case someone finds better sources for the dates cited there, but I'm replacing it in the article with the chart below, because I think my chart (which has more rows, and data that are in some cases dramatically different) is very solidly sourced.

However, there is a much better source for all sorts of information about the 1700 earthquake, the associated tsunami, and Cascadia in general:

Brian F Atwater (2005). The Orphan Tsunami of 1700 — Japanese Clues to a Parent Earthquake in North America (U.S. Geological Survey Professional Paper 1707 ed.). Seattle and London: University of Washington Press. ISBN 0-295-98535-6. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

For purposes of the table, we don't need the whole book, just the timeline chart on page 100 of the book:

Brian F Atwater (2005). The Orphan Tsunami of 1700 — Japanese Clues to a Parent Earthquake in North America (PDF) (U.S. Geological Survey Professional Paper 1707 ed.). Seattle and London: University of Washington Press. p. 100 (timeline diagram). ISBN 0-295-98535-6. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

In turn, that chart cites this source (from the pages noted): The book cites an earlier journal article, with some of the same authors, specifically Figures 10 and 11 on pages 341 and 341 (of an article that runs pages 331 through 350):

Brian F Atwater (2003). "Earthquake Recurrence Inferred from Paleoseismology" (PDF). Developments in Quaternary Science. 1. Elsevier BV: 341, 342. doi:10.1016/S1571-0866(03)01015-7. ISSN 1571-0866. Retrieved 2011-03-15. {{cite journal}}: More than one of |pages=, |at=, and |page= specified (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)

Somewhat annoyingly, the citation template doesn't let me show that the entire article occupies pages 331 through 350, but the only parts that matter are Figures 10 and 11, on pages 341 and 342 (with more details in the appendix on pages 349 and 350). This citation twists the template to generate a reference that looks decent, but the citation looks pretty ugly behind the scenes:

Brian F Atwater (2003). "Earthquake Recurrence Inferred from Paleoseismology" (PDF). Developments in Quaternary Science. 1. Elsevier BV. Figures 10 and 11 (pp 341, 342); article pp 331-350. doi:10.1016/S1571-0866(03)01015-7. ISSN 1571-0866. Retrieved 2011-03-15. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

Great Earthquakes

estimated year		interval
(book's timeline)	(article's carbon dates)	(years)
Y about 9 pm, January 26, 1700 (NS)		780
W 780-1190 CE (985)	1040-1120 age; 960-880 CE (920)	210
U 690-730 CE (710)	1246-1454 age; 754-546 CE (650)	325
S 350-420 CE (385)	1681-1755 age; 319-245 CE (282)	914
N 660-440 BCE (550 BCE)	2449-2610 age; 449-610 BCE (529 BCE)	396
L 980-890 BCE (935 BCE)	2777-2909 age; 777-909 BCE (843 BCE)	248
J 1440-1340 BCE (1390 BCE)	3148-3217 age; 1148-1217 BCE (1183 BCE)	unknown

Anyway, the charts in both sources include ranges of years (except for the 1700 quake, which has been isolated to a specific date), since the sources show spans of years. I got the year spans from the timeline in the book (The Orphan Tsunami of 1700) because its images are much clearer, but I use the strata names (Y, W, U, S, N, L, J; as sorting keys) from the article ("Earthquake Recurrence Inferred from Paleoseismology").

The book's timeline doesn't have exact year numbers on it, just gray bars; I converted those to dates by counting pixels in the images. The article has both a timeline and before-2000 ages±uncertainty; for those I calculated age±uncertainty from the sample dates in Figure 11, and subtracted for CE or BCE dates for the table. To calculate intervals, I found the middle of each range (parenthesized) as best-estimate date (using the narrower range; bolded), and subtracting consecutive dates.

In the table on this talk page, I show exact years, but in the article I round to nearest tens (except in the case of 1700) because all of the uncertainties are in the tens of years. (I rounded 385 CE and 935 BCE toward 282 CE and 843 BCE, respectively.)

I hope calculating years the way I've done doesn't stray into original research territory, but I admit this pushes the limits of WP:CALC, since it shouldn't take this much to explain how I converted well-sourced material into tabular form.

The table isn't as pretty as I'd like; I think it would look better without the border between the first and second rows of the column headings (and without a border between the citations), but I'm not sure how to do that without losing the desirable borders.

— Steve98052 (talk) 03:02, 16 March 2011 (UTC)

Oops, I forgot to get back to the BBC citation. The on-screen scientist mentions "about 600 BC", "about AD 400", "about AD 700", and 1700. Those correspond well with the new table's circa 529 BCE, 385 CE, 710 CE, and 1700 quakes – better than with the previous table.

The book has the text "Soil inconspicuous in most outcrops" in reference to the circa 920 CE quake. It says "Soil below water in photo" in reference to the circa 1183 BCE quake, and the soil layer for the circa 935 BCE quake may also be inaccessible to the on-screen scientist. That suggests that the new table improves on the old. Even if I've pushed WP:CALC somewhat, I think it's better than the old table, which lacks any citations.

— Steve98052 (talk) 03:24, 16 March 2011 (UTC)

Major cities affected by a disturbance in this subduction zone should be revised.

This is being picky, but I would suggest that the list of cities affected by a subduction zone earthquake be revised, specifically Sacramento should not be included in the list. Sacramento like San Francisco would likely feel the earthquake but is 200+ miles south of the southern edge of the subduction zone and therefore the expected impact would be significantly less compared with a city such as Seattle or Portland.

The article that is referencing the statement is by a journalist rather than a scientist, I would question whether this should be used as a reference for a scientific matter?? — Preceding unsigned comment added by 216.16.236.14 (talk) 16:46, 2 April 2012 (UTC)

Recurrence rate

For anyone interested in taking a closer look at the scientific thinking regarding recurrence rate: take look at USGS Open-File Report 2011–1310. Additional comment at Talk:1700 Cascadia earthquake#Resource. ~ J. Johnson (JJ) (talk) 23:29, 25 May 2012 (UTC)

History

There ought to be a history section, as its discovery is really interesting—its existence was not fully confirmed until the 80s/90s. During a tsunami that hit the coast of Japan, it had been referred to as an "orphan tsunami" until researchers lined up dynastic dates with the Gregorian calendar. Further researchers compiled oral history among American Indian tribes to approximate a location of this earthquake, since Europeans (and writing systems) hadn't arrived there by that point. Geologists eventually confirmed it after they came upon a "ghost forest" in the Copalis River, remnants of 300-year-old trees that had suddenly been killed by the ground plummeting on the fault, and after analyzing rock samples in that area and on the sea floor.

Some sources:

reflist

- SweetNightmares 04:23, 15 July 2015 (UTC)