Ground-Motion Attenuation Equations for Earthquakes on the Cascadia Subduction Zone

1991 ◽  
Vol 7 (2) ◽  
pp. 201-236 ◽  
Author(s):  
C. B. Crouse
Keyword(s):  
Data Base ◽  
Subduction Zone ◽  
Ground Motion ◽  
Pacific Northwest ◽  
Puget Sound ◽  
Response Spectra ◽  
Cascadia Subduction Zone ◽  
Regression Equations ◽  
Median Response ◽  
The Pacific

An extensive ground-motion data base was compiled for earthquakes occurring in subduction zones considered representative of the Cascadia subduction zone in the Pacific Northwest. The attenuation characteristics of horizontal peak ground accelerations (PGA) and 5 percent damped pseudovelocity (PSV) were studied for various subsets of the total data base. These data suggested that the PGA tend to saturate at small source-to-site distances and large magnitudes. When unprocessed data were added to the data base, the attenuation of PGA with distance was found to be greater than the attenuation observed for the processed data only, a result which was attributed to the selection of only the stronger motion records for processing. The results of the data analysis were used to establish the proper form of regression equations for estimating PGA and PSV at firm-soil sites in the Pacific Northwest. A total of 697 PGA components and 235 PSV components were selected for the regressions. The resulting equation for estimating PGA in gals was ln (PGA) = 6.36 + 1.76M − 2.73 ln (R + 1.58 exp (0.608M) + 0.00916h, σ=0.773 where M is moment magnitude, R is center-of-energy-release distance in km, h is focal depth in km, and σ is the standard error of ln (PGA). Although σ was relatively large, the residuals from the regressions appeared to decrease with increasing M and R. The results of the PSV regressions showed that the M coefficient and the coefficient of the f(R, M) attenuation term generally increased with period, which is consistent with regression results reported by others. The regression equations were reasonably accurate in predicting the response spectra of accelerograms recorded at Olympia and Seattle, Washington during the 1949 and 1965 Puget Sound earthquakes, but overestimated the spectra of the weaker motions recorded at Tacoma and Portland during the latter event. The median response spectra predicted by these equations for a Washington Coastal Ranges site were similar to the spectra computed by Heaton and Hartzell based on their simulations of ground motions from hypothetical giant earthquakes (M = 9.0 and 9.5) in the Pacific Northwest.

Summary of Coastal Geologic Evidence for past Great Earthquakes at the Cascadia Subduction Zone

1995 ◽  
Vol 11 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Brian F. Atwater ◽  
Alan R. Nelson ◽  
John J. Clague ◽  
Gary A. Carver ◽  
David K. Yamaguchi ◽  
...  
Keyword(s):  
British Columbia ◽  
North America ◽  
Subduction Zone ◽  
Forest Soils ◽  
Pacific Coast ◽  
Cascadia Subduction Zone ◽  
Level Change ◽  
The Past ◽  
The Pacific ◽  
Juan De Fuca

Earthquakes in the past few thousand years have left signs of land-level change, tsunamis, and shaking along the Pacific coast at the Cascadia subduction zone. Sudden lowering of land accounts for many of the buried marsh and forest soils at estuaries between southern British Columbia and northern California. Sand layers on some of these soils imply that tsunamis were triggered by some of the events that lowered the land. Liquefaction features show that inland shaking accompanied sudden coastal subsidence at the Washington-Oregon border about 300 years ago. The combined evidence for subsidence, tsunamis, and shaking shows that earthquakes of magnitude 8 or larger have occurred on the boundary between the overriding North America plate and the downgoing Juan de Fuca and Gorda plates. Intervals between the earthquakes are poorly known because of uncertainties about the number and ages of the earthquakes. Current estimates for individual intervals at specific coastal sites range from a few centuries to about one thousand years.

Ella Rhoads Higginson

2021 ◽  
Keyword(s):  
World War I ◽  
New England ◽  
Pacific Northwest ◽  
Private School ◽  
White Women ◽  
White Male ◽  
Puget Sound ◽  
Her Family ◽  
The Pacific ◽  
City Newspaper

Ella Rhoads Higginson (b. 1862?–d. 1940) was born in Council Grove, Kansas, a launching point for westward movement of settler colonialists. When she was a child, her family moved to Oregon, traveling in a wagon train following the old Oregon Trail. The family eventually settled in Oregon City, where she was educated in private school. Ella’s strong interests in reading and writing began early. Her parents possessed a substantial library that included books by Irving, Longfellow, Shakespeare, and Tennyson. Ella began writing when she was eight. Her first publication, the poem “Dreams of the Past,” appeared in The Oregon City newspaper when she was fourteen. The following year she began work on The Oregon City Enterprise newspaper, learning typesetting and editorial writing. She also started publishing fiction. In 1885, she married Russell Carden Higginson, a businessman who was a cousin to New England author Thomas Wentworth Higginson. The couple moved north to Whatcom (later Bellingham), Washington, where Higginson lived for fifty-two years until her death. There she devoted herself to writing. She soon became the first influential Pacific Northwest author. People around the world were introduced to the region when they read Higginson’s award-winning writing. Her descriptions of majestic mountains, vast forests, and the scenic waters of the Puget Sound presented the then-remote, unfamiliar Pacific Northwest to eager readers. Her characterizations of white women and men who inhabited the region revealed what life was like in this part of the nation as opposed to regions such as New England. Higginson’s celebrated writings were the first to place the Pacific Northwest on the literary map. Her talent was widely recognized. The prestigious Macmillan Company, which became her publisher, approached her seeking to print her work. She was awarded prizes from magazines such as Collier’s and McClure’s. Her poems were set to music and performed internationally. She published over eight hundred works in her lifetime. However, World War I altered the means of production, resulting in books going out of print and diminishing reputations of well-known authors, especially writers of color and women. Most of Higginson’s books went out of print. After the war, new editors, mostly white men, managed US newspapers, periodicals, and publishing companies. Largely uninterested in prewar authors, they sought writing from nascent literary movements such as Modernism while also promoting works by overlooked white male authors such as Melville. Higginson’s reputation faded in the last decades of her life. By the time she was chosen first Poet Laureate of Washington State in 1931, she and her work were largely remembered only in the Pacific Northwest. When she died in 1940, she was almost completely forgotten. In the 21st century, Higginson and her writings are returning to literary distinction.

Geoarchaeological Perspectives on the “Millennial Series” of Earthquakes in the Southern Puget Lowland, Washington, USA

Radiocarbon ◽  
2015 ◽  
Vol 57 (5) ◽  
pp. 917-941 ◽  
Author(s):  
Ian Hutchinson
Keyword(s):  
Pacific Northwest ◽  
Puget Sound ◽  
Low Frequency ◽  
Archaeological Sites ◽  
Hood Canal ◽  
The Pacific ◽  
Abrupt Changes ◽  
Western Washington ◽  
Socioeconomic Consequences ◽  
Large Earthquakes

Surface-breaking ruptures on shallow crustal faults in the southern Puget Lowland in western Washington State about a millennium ago prompted abrupt changes in land level and triggered tsunamis in Puget Sound. The displacement on the Seattle fault most likely occurred in the 1050–1020 cal BP interval. Structures further south (the Tacoma and Olympia faults, and one or more faults in the southern Hood Canal zone) ruptured at about the same time, or slightly earlier. The low frequency of radiocarbon ages from archaeological sites in the region in the aftermath of the “millennial series” of earthquakes, when compared to bootstrapped samples from a database of 1255 ages from the Pacific Northwest as a whole, suggests that these very large earthquakes had significant socioeconomic consequences. The cultural record from coastal archaeological sites shows that although survivors camped on the shore in the aftermath, many coastal villages appear to have been abandoned, and were not reoccupied for several centuries. There is little evidence, however, to suggest that people migrated from southern Puget Sound to neighboring areas, and no evidence of social conflict in the adjacent areas that might have served as havens.

Crash Theory: Entrapments of Conservation Drones and Endangered Megafauna

2020 ◽  
pp. 016224392092035
Author(s):  
Adam Fish
Keyword(s):  
Machine Learning ◽  
Sri Lanka ◽  
Endangered Species ◽  
Pacific Northwest ◽  
Puget Sound ◽  
Training Data ◽  
Electromagnetic Spectrum ◽  
The United Kingdom ◽  
Nature And Culture ◽  
The Pacific

Drones deployed to monitor endangered species often crash. These crashes teach us that using drones for conservation is a contingent practice ensnaring humans, technologies, and animals. This article advances a crash theory in which pilots, conservation drones, and endangered megafauna are relata, or related actants, that intra-act, cocreating each other and a mutually constituted phenomena. These phenomena are entangled, with either reciprocal dependencies or erosive entrapments. The crashing of conservation drones and endangered species requires an ethics of care, repair, or reworlding. Diffractions, disruptions that expose difference, result from crashes and reveal the precarious manner by which technologies, laws, and discourses bring nature and culture together. To support crash theory, this article presents three ethnographic cases. A drone crash in the United Kingdom near white rhinoceroses while building machine learning training data exhibits the involvement of the electromagnetic spectrum; the threat of crashes in the Pacific Northwest near Puget Sound orcas discloses the impacts of drone laws; and drone crashes in Sri Lanka among Asian elephants presents the problems of technoliberal ideals around programming natural worlds. Throughout the article, a methodology is developed, parallelism, which attends to the material similarities in lateral phenomena.

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