Seismic surface waves and the crustal structure of the Pacific region*

1934 ◽  
Vol 24 (3) ◽  
pp. 231-302
Author(s):  
Dean S. Carder
Keyword(s):  
North America ◽  
Surface Waves ◽  
Pacific Islands ◽  
Long Waves ◽  
The Arctic ◽  
Focal Region ◽  
Western North America ◽  
Central Pacific ◽  
Natural Period ◽  
The Pacific

summary The favorable location of Berkeley on the eastern margin of the Pacific makes possible a comparative study of surface waves coming directly from the epicenter to that station over paths that are purely Pacific or purely continental. Records of 378 earthquakes dating from November, 1910, to May, 1934, have been used in this study. Speeds and period of the initial impulses of Love waves have been measured and associated with wave-velocity. These waves show normal dispersion, the long waves having the greater speeds. Speeds over oceanic paths are higher than over continental paths, the difference diminishing with an increase in the wave-length. For short or long waves, they are about the same over all Pacific paths, but waves having intermediate periods (30 or 40 seconds) cross under the Aleutian deep faster than under the Polynesian Pacific. The data indicate for the crustal thicknesses under western North America and the Pacific the following approximate values: granite 20 kilometers, gabbro 40 kilometers, under western North America; basalt 25 kilometers, dunite 20 kilometers, under the Aleutian deep; basalt 30 kilometers, dunite 25 kilometers under Polynesia; and intermediate values under the remainder of the Pacific. A third discontinuity under the continent at depths somewhat greater than 60 kilometers is indicated. If the sub-Pacific is assumed to be single-layered, thicknesses of 35 to 45 kilometers form the best fit to the data. The thickness of the crust underlying the Pacific Islands is probably about 10 kilometers greater than that underlying the deeps of the North Pacific. Movements associated with Rayleigh waves apparently have their closest approach to theoretical conditions over central Pacific paths. The dominant periods in the coda are 8 to 9, 10, 13, and 16 seconds. The longer periods are dominant at the greater distances. The increase in period with distance is a discontinuous, step-like function. The structure underlying the Aleutian deep apparently is opaque to 13-second periods in the Rayleigh wave, and the central Pacific and possibly the Atlantic structure seems to be unfavorable in the transmission of waves having this period. Vibrations in the natural period or overtones thereof set up in the focal region being eventually transmitted as sympathetic vibrations to the region of the station seems to be a logical explanation for the dominant groupings in the coda. Should any section of the path be out of sympathy with a given period, this period would probably become subordinate if not lost. The natural period of a portion of the Arctic region, including Alaska, seems to be different from other parts of the world. The natural period of the San Francisco Bay region, or its dominant overtone, is observed to be about eight seconds.

Predictable Patterns of Wintertime Surface Air Temperature in Northern Hemisphere and Their Predictability Sources in the SEAS5

2020 ◽  
Vol 33 (24) ◽  
pp. 10743-10754
Author(s):  
Hongdou Fan ◽  
Lin Wang ◽  
Yang Zhang ◽  
Youmin Tang ◽  
Wansuo Duan ◽  
...  
Keyword(s):  
North America ◽  
Northern Hemisphere ◽  
Air Temperature ◽  
Southern Oscillation ◽  
Arctic Sea Ice ◽  
Prediction Skill ◽  
The Arctic ◽  
The Tibetan Plateau ◽  
Central Pacific ◽  
The Pacific

AbstractBased on 36-yr hindcasts from the fifth-generation seasonal forecast system of the European Centre for Medium-Range Weather Forecasts (SEAS5), the most predictable patterns of the wintertime 2-m air temperature (T2m) in the extratropical Northern Hemisphere are extracted via the maximum signal-to-noise (MSN) empirical orthogonal function (EOF) analysis, and their associated predictability sources are identified. The MSN EOF1 captures the warming trend that amplifies over the Arctic but misses the associated warm Arctic–cold continent pattern. The MSN EOF2 delineates a wavelike T2m pattern over the Pacific–North America region, which is rooted in the tropical forcing of the eastern Pacific-type El Niño–Southern Oscillation (ENSO). The MSN EOF3 shows a wavelike T2m pattern over the Pacific–North America region, which has an approximately 90° phase difference from that associated with MSN EOF2, and a loading center over midlatitude Eurasia. Its sources of predictability include the central Pacific-type ENSO and Eurasian snow cover. The MSN EOF4 reflects T2m variability surrounding the Tibetan Plateau, which is plausibly linked to the remote forcing of the Arctic sea ice. The information on the leading predictable patterns and their sources of predictability is further used to develop a calibration scheme to improve the prediction skill of T2m. The calibrated prediction skill in terms of the anomaly correlation coefficient improves significantly over midlatitude Eurasia in a leave-one-out cross-validation, implying a possible way to improve the wintertime T2m prediction in the SEAS5.

Supplemental material: Cenozoic to Recent plate configurations in the Pacific Basin: Ridge subduction and slab window magmatism in western North America

2006 ◽  
Author(s):  
J.K. Madsen ◽  
D.J. Thorkelson ◽  
R.M. Friedman ◽  
D.D. Marshall
Keyword(s):  
North America ◽  
Pacific Basin ◽  
Western North America ◽  
File Size ◽  
Tectonic Model ◽  
Ridge Subduction ◽  
The Pacific ◽  
Northwestern North America ◽  
Slab Window

Geosphere, February 2006, v. 2, p. 11-34, doi: 10.1130/GES00020.1. Movie 1 - Tectonic model for the Pacific Basin and northwestern North America from 53 Ma to 39 Ma. The file size is 1.3 MB.

A new genus of cassiduloid echinoid from the lower Eocene of the Pacific coast of western North America and a new report of Cassidulus ellipticus Kew, 1920, from the lower Eocene of Baja California Sur, Mexico

1995 ◽  
Vol 69 (3) ◽  
pp. 509-515 ◽  
Author(s):  
Richard L. Squires ◽  
Robert A. Demetrion
Keyword(s):  
North America ◽  
New Genus ◽  
Baja California ◽  
Pacific Coast ◽  
Middle Part ◽  
Baja California Sur ◽  
Western North America ◽  
Lower Eocene ◽  
Shallow Marine ◽  
The Pacific

The cassiduloid echinoid Calilampas californiensis n. gen. and sp. is described from middle lower Eocene (“Capay Stage”) shallow-marine sandstones in both the middle part of the Bateque Formation, Baja California Sur, Mexico, and the lower part of the Llajas Formation, southern California. The new genus is tentatively placed in family Pliolampadidae. The cassiduloid Cassidulus ellipticus Kew, 1920, previously known only from the “Capay Stage” in California, is also present in “Capay Stage” shallow-marine sandstones of the Bateque Formation.

The Inland Penetration of Atmospheric Rivers over Western North America: A Lagrangian Analysis

2015 ◽  
Vol 143 (5) ◽  
pp. 1924-1944 ◽  
Author(s):  
Jonathan J. Rutz ◽  
W. James Steenburgh ◽  
F. Martin Ralph
Keyword(s):  
Water Vapor ◽  
North America ◽  
Pacific Coast ◽  
Water Vapor Transport ◽  
Western North America ◽  
Lagrangian Analysis ◽  
Initial Water ◽  
Atmospheric Rivers ◽  
The Pacific ◽  
Synoptic Conditions

Abstract Although atmospheric rivers (ARs) typically weaken following landfall, those that penetrate inland can contribute to heavy precipitation and high-impact weather within the interior of western North America. In this paper, the authors examine the evolution of ARs over western North America using trajectories released at 950 and 700 hPa within cool-season ARs along the Pacific coast. These trajectories are classified as coastal decaying, inland penetrating, or interior penetrating based on whether they remain within an AR upon reaching selected transects over western North America. Interior-penetrating AR trajectories most frequently make landfall along the Oregon coast, but the greatest fraction of landfalling AR trajectories that eventually penetrate into the interior within an AR is found along the Baja Peninsula. In contrast, interior-penetrating AR trajectories rarely traverse the southern “high” Sierra. At landfall, interior-penetrating AR trajectories are associated with a more amplified flow pattern, more southwesterly (vs westerly) flow along the Pacific coast, and larger water vapor transport (qυ). The larger initial qυ of interior-penetrating AR trajectories is due primarily to larger initial water vapor q and wind speed υ for those initiated at 950 and 700 hPa, respectively. Inland- and interior-penetrating AR trajectories maintain large qυ over the interior partially due to increases in υ that offset decreases in q, particularly in the vicinity of topographical barriers. Therefore, synoptic conditions and trajectory pathways favoring larger initial qυ at the coast, limited water vapor depletion by orographic precipitation, and increases in υ over the interior are keys to differentiating interior-penetrating from coastal-decaying ARs.

scholarly journals Glacier retreat creating new Pacific salmon habitat in western North America

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kara J. Pitman ◽  
Jonathan W. Moore ◽  
Matthias Huss ◽  
Matthew R. Sloat ◽  
Diane C. Whited ◽  
...  
Keyword(s):  
North America ◽  
Climate Models ◽  
Pacific Salmon ◽  
Global Climate ◽  
Global Climate Models ◽  
Glacier Retreat ◽  
Western North America ◽  
Mountain Ranges ◽  
Proactive Management ◽  
The Pacific

AbstractGlacier retreat poses risks and benefits for species of cultural and economic importance. One example is Pacific salmon (Oncorhynchus spp.), supporting subsistence harvests, and commercial and recreational fisheries worth billions of dollars annually. Although decreases in summer streamflow and warming freshwater is reducing salmon habitat quality in parts of their range, glacier retreat is creating new streams and lakes that salmon can colonize. However, potential gains in future salmon habitat associated with glacier loss have yet to be quantified across the range of Pacific salmon. Here we project future gains in Pacific salmon freshwater habitat by linking a model of glacier mass change for 315 glaciers, forced by five different Global Climate Models, with a simple model of salmon stream habitat potential throughout the Pacific Mountain ranges of western North America. We project that by the year 2100 glacier retreat will create 6,146 (±1,619) km of new streams accessible for colonization by Pacific salmon, of which 1,930 (±569) km have the potential to be used for spawning and juvenile rearing, representing 0 to 27% gains within the 18 sub-regions we studied. These findings can inform proactive management and conservation of Pacific salmon in this era of rapid climate change.

scholarly journals Using oxygen and hydrogen stable isotopes to track the migratory movement of Sharp-shinned Hawks (Accipiter striatus) along Western Flyways of North America

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0226318
Author(s):  
Elizabeth A. Wommack ◽  
Lisa C. Marrack ◽  
Stefania Mambelli ◽  
Joshua M. Hull ◽  
Todd E. Dawson
Keyword(s):  
Stable Isotope ◽  
North America ◽  
Large Scale ◽  
Pacific Coast ◽  
Isotope Analysis ◽  
Western North America ◽  
Migration Routes ◽  
The Pacific ◽  
Accipiter Striatus ◽  
Hydrogen And Oxygen Isotope

The large-scale patterns of movement for the Sharp-shinned Hawk (Accipiter striatus), a small forest hawk found throughout western North America, are largely unknown. However, based on field observations we set out to test the hypothesis that juvenile migratory A. striatus caught along two distinct migration routes on opposite sides of the Sierra Nevada Mountains of North America (Pacific Coast and Intermountain Migratory Flyways) come from geographically different natal populations. We applied stable isotope analysis of hydrogen (H) and oxygen (O) of feathers, and large scale models of spatial isotopic variation (isoscapes) to formulate spatially explicit predictions of the origin of the migrant birds. Novel relationships were assessed between the measured hydrogen and oxygen isotope values of feathers from A. striatus museum specimens of known origin and the isoscape modeled hydrogen and oxygen isotope values of precipitation at those known locations. We used these relationships to predict the origin regions for birds migrating along the two flyways from the measured isotope values of migrant’s feathers and the associated hydrogen and oxygen isotopic composition of precipitation where these feathers were formed. The birds from the two migration routes had overlap in their natal/breeding origins and did not differentiate into fully separate migratory populations, with birds from the Pacific Coast Migratory Flyway showing broader natal geographic origins than those from the Intermountain Flyway. The methodology based on oxygen isotopes had, in general, less predictive power than the one based on hydrogen. There was broad agreement between the two isotope approaches in the geographic assignment of the origins of birds migrating along the Pacific Coast Flyway, but not for those migrating along the Intermountain Migratory Flyway. These results are discussed in terms of their implications for conservation efforts of A. striatus in western North America, and the use of combined hydrogen and oxygen stable isotope analysis to track the movement of birds of prey on continental scales.

A revision of the lichen genus Platismatia (Parmeliaceae) in Russia, with a key to the species

2021 ◽  
Vol 55 (1) ◽  
pp. 179-194
Author(s):  
E. S Kuznetsova ◽  
I. S. Stepanchikova ◽  
I. F. Skirina ◽  
S. V. Chesnokov ◽  
D. E. Himelbrant
Keyword(s):  
North America ◽  
Relevant Literature ◽  
Pacific Region ◽  
Western North America ◽  
Northeastern Asia ◽  
Commander Islands ◽  
The Pacific ◽  
Herbarium Collections

The paper presents the results of the study on Platismatia species in Russia. The genus Platismatia counts 11 species, distributed mainly in the Pacific region, with some endemics of western North America and northeastern Asia. Six species were known from Russia by the beginning of our studies, but a revision of the herbarium collections showed that three species (P. erosa, P. herrei, and P. lacunosa) were reported erroneously. Based on morphological and chemotaxonomical (HPTLC) examination of the herbarium collections and our own material, as well as the study of relevant literature, four species of Platismatia are here accepted for Russia: P. glauca, P. interrupta, P. lacunosa, and P. norvegica. Platismatia lacunosa is reported here as a new for Russia from the Commander Islands. The distribution of P. glauca and P. interrupta is clarified. A key to all species of the genus reported from Russia and brief descriptions of the Russian species are presented.

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