Sources by Brian Atwater

SOURCES – Earthquake Ecologists I

A biography of James Graham Cooper (1830–1902) includes a timeline of his career and a comprehensive list of his published and unpublished works1. These include journals spanning his months at Willapa Bay2,3 and a botanical chapter in the Northern Pacific railroad report4. The spruce stumps are described in a journal entry for March 10, 1854, and the western red cedar trunks on page 22 of the botany chapter.

Stretching of rock above an inclined fault produced subsidence on a grand scale during the 1964 Alaska earthquake (p. 64–66 of ref 5; next geological installment of Nature Notes). The same process accounts for the tidal submergence and consequent burial of forest and marsh soils at estuaries along the Pacific coast above the Cascadia Subduction Zone (p. 16–17 in ref 6). In the railroad report Cooper inferred that forested land had sunk gradually4. Today, as summarized in ref 6, it has become clear that the entire landscape in southwest Washington dropped abruptly. This sudden lowering of land allowed tides to drown lowland forests and estuarine marshes.

Animations7 depict much of the geology mentioned in this set of Nature Notes.

SOURCES – Earthquake Ecologists II

Early uses of “subduction” cited in the Oxford English Dictionary include a 17th-century comment on purgatives for gout (p. 18–19 in ref8). The plate-tectonic revolution of the 1960s created demand for a term to denote the underthrusting of a continental margin or island arc by an oceanic plate9,10.

The source of the 1964 Alaska earthquake was either a steep fault or a gently sloping fault, as judged from the first motions at seismometers. Some of the field evidence for land-level change was found roughly compatible with a steep fault, provided the seismic slip extended from a depths of about 15 km to depths 100–200 km11. Aftershock locations instead painted in a gently sloping fault at depths of 30 km of less5,12.

The evidence for a subduction zone in Cascadia includes reconstructed plate motions13,14. The remains of tidally drowned herbaceous plants and trees provide datable evidence for lowering of coastal land during Cascadia earthquakes15. Death dates from trunks of western red cedar, mentioned in a previous Nature Note, give confidence that the most recent of these quakes occurred in January 170016, and that it was large enough for an associated tsunami to explain documented flooding and damage in Japan6,17.

SOURCES – Earthquake Ecologists III

The exchange in London between Maria Graham (1785–1842) and George Bellas Greenough (1778–1855) was reproduced in an 1835 issue of the American Journal of Science and Arts, in New Haven18. A transcript is available from a website on Graham and her work19.

Graham has been viewed as a disinterested observer whose professed indifference to Greenough’s theory of uplift reflects a meager background in Earth science. In this view the main story is Greenough attacking Graham to get at Charles Lyell, who in his “Principles of Geology” had adopted her Chilean findings—and who did not rise to her defense20.

Recent commentary finds Graham more engaged in natural history that her riposte to Greenough may suggest. Graham, in this view, recognized the Chilean earthquake as more than a curiosity, surveyed its effects carefully, and had the drive and talent to report on them, through an intermediary, to the male-only Geological Society in London21.

The 1960 Chilean earthquake and 1964 Alaskan earthquake were accompanied by uplift mainly offshore and subsidence mainly onshore5,22. This deformation pattern serves as the initial condition in tsunami simulations in Cascadia23, including those used in design of the rooftop refuge recently completed in Westport24.