Index of stress data for the North American and parts of the Pacific plate

To accommodate the relative motion across the North American-Pacific plate boundary predicted by global plate solutions, significant deformation on faults other than the San Andreas is necessary. In central California, this deformation is thought to include distributed compression perpendicular to the San Andreas as well as right-lateral strike-slip motion parallel to the San Andreas on faults such as the San Gregorio/Hosgri system. A self-consistent set of VLBI observations from experiments beginning in October 1982 is used to determine the vector rate of change of station position at central California VLBI sites Ovro, Mojave, Vandenberg, Fort Ord, Presidio, and Point Reyes. To estimate VLBI station positions, a procedure is used that minimizes the uncertainties in defining a reference frame by including a priori geologic and geodetic information. The vector rate of change of station positions provides constraints on the integrated deformation rates between stations. Geologic and geophysical data suggest that the rate and mode of deformation varies on both local and regional scales. Thus, the VLBI derived results are interpreted in the context of an overall tectonic framework by examining geologic and ground-based geodetic data.

Download Full-text

Intraseasonal and Interannual Variability in North American Storm Tracks and Its Relationship to Equatorial Pacific Variability

Monthly Weather Review ◽

10.1175/mwr-d-12-00322.1 ◽

2013 ◽

Vol 141 (10) ◽

pp. 3610-3625 ◽

Cited By ~ 42

Author(s):

Kevin M. Grise ◽

Seok-Woo Son ◽

John R. Gyakum

Keyword(s):

North America ◽

Interannual Variability ◽

North American ◽

Southern Oscillation ◽

Extratropical Cyclones ◽

The North ◽

The Pacific ◽

Cyclone Tracks ◽

Lagrangian Tracking ◽

The North Atlantic Oscillation

Abstract Extratropical cyclones play a principal role in wintertime precipitation and severe weather over North America. On average, the greatest number of cyclones track 1) from the lee of the Rocky Mountains eastward across the Great Lakes and 2) over the Gulf Stream along the eastern coastline of North America. However, the cyclone tracks are highly variable within individual winters and between winter seasons. In this study, the authors apply a Lagrangian tracking algorithm to examine variability in extratropical cyclone tracks over North America during winter. A series of methodological criteria is used to isolate cyclone development and decay regions and to account for the elevated topography over western North America. The results confirm the signatures of four climate phenomena in the intraseasonal and interannual variability in North American cyclone tracks: the North Atlantic Oscillation (NAO), the El Niño–Southern Oscillation (ENSO), the Pacific–North American pattern (PNA), and the Madden–Julian oscillation (MJO). Similar signatures are found using Eulerian bandpass-filtered eddy variances. Variability in the number of extratropical cyclones at most locations in North America is linked to fluctuations in Rossby wave trains extending from the central tropical Pacific Ocean. Only over the far northeastern United States and northeastern Canada is cyclone variability strongly linked to the NAO. The results suggest that Pacific sector variability (ENSO, PNA, and MJO) is a key contributor to intraseasonal and interannual variability in the frequency of extratropical cyclones at most locations across North America.

Download Full-text

Toward Identifying Subseasonal Forecasts of Opportunity Using North American Weather Regimes

Monthly Weather Review ◽

10.1175/mwr-d-19-0285.1 ◽

2020 ◽

Vol 148 (5) ◽

pp. 1861-1875

Author(s):

Andrew W. Robertson ◽

Nicolas Vigaud ◽

Jing Yuan ◽

Michael K. Tippett

Keyword(s):

North American ◽

El Niño ◽

Geopotential Height ◽

Large Scale ◽

El Nino ◽

Lead Times ◽

Seasonal Forecasts ◽

The North ◽

The Pacific ◽

Graphical Tool

Abstract Large-scale atmospheric circulation regime structures are used to diagnose subseasonal forecasts of wintertime geopotential height fields over the North American sector, from the NCEP CFSv2 model. Four large-scale daily circulation regimes derived from reanalysis 500-hPa geopotential height data using K-means clustering are used as a low-dimensional basis for diagnosing the model’s forecasts up to 45 days ahead. On average, hindcast skill in regime space is found to be limited to 10–15 days ahead, in terms of anomaly correlation of 5-day averages of regime counts, over the 1999–2010 period. However, skill up to 30 days ahead is identified in individual winters, and intraseasonal episodes of high skill are identified using a forecast-evolution graphical tool. A striking vacillation between the West Coast and Pacific ridge patterns during December–January 2008/09 is shown to be predicted 20–25 days in advance, illustrating the possibility to identify “forecasts of opportunity” when subseasonal forecast skill is much higher than the average. The forecast-evolution tool also provides insight into the poor seasonal forecasts of California precipitation by operational centers during the 2015/16 El Niño winter. The Pacific trough regime is shown to be greatly overpredicted beyond 1–2 weeks in advance during the 2015/16 winter, with weather-scale features dominating the forecast evolution at shorter lead times. A similar though less extreme situation took place during the weaker El Niño of 2009/10, with the Pacific trough overforecast at S2S lead times.

Download Full-text

Structural Characteristics and Mechanism of the Horsetail Structure in China Offshore Basins: Case Studies from Liaodong Bay Area, Bohai Bay Basin and Weixinan Area, Beibuwan Basin

10.5194/egusphere-egu2020-4581 ◽

2020 ◽

Author(s):

Jie Zhang ◽

Zhiping Wu ◽

Yanjun Cheng

Keyword(s):

Structural Characteristics ◽

Strike Slip ◽

Pacific Plate ◽

Strike Slip Fault ◽

Bohai Bay ◽

Liaodong Bay ◽

Clockwise Rotation ◽

Bay Area ◽

The North ◽

The Pacific

<p>The horsetail structure, also named brush structure, generally refers to a sets of secondary faults converged to the primary fault on the plane. Based on 2-D and 3-D seismic data, the structural characteristics, evolution and mechanism of the horsetail structure of Liaodong Bay area in Bohai Bay Basin and Weixinan area in Beibuwan Basin are analyzed. In the Liaodong Bay area, the primary fault of the horsetail structure is the NNE-striking branch fault of Tan-Lu strike-slip fault zone. The NE-striking secondary extensional faults converged to the primary strike-slip fault. Fault activity analysis shows that both the primary and secondary faults intensively activated during the third Member of the Shahejie Formation (42~38 Ma). In the Weixinan area, the NE-striking Weixinan fault is the primary fault of the horsetail structure, which is an extensional fault. A large amount of EW-striking secondary extensional faults converged to the primary NE-striking Weixinan fault. Fault activity analysis shows that NE-striking primary fault intensively activated during the second Member of the Liushagang Formation (48.6~40.4 Ma), whereas the EW-striking secondary faults intensively activated during the Weizhou Formation (33.9~23 Ma). The different structure and evolution of the horsetail structure in the Liaodong Bay area and Weixinan area are mainly resulted from the regional tectonic settings. About 42 Ma, the change of subduction direction of the Pacific plate and the India-Eurasian collision resulted in the right-lateral strike-slip movement of NNE-striking Tan-Lu fault and the formation of NE-striking extensional faults along the bend of the strike-slip fault, therefore, the horsetail structure of Liaodong Bay area formed. However, the formation of the horsetail structure of Weixinan area is related to the clockwise rotation of extension stress in the South China Sea (SCS): 1) During Paleocene to M. Eocene (65~37.8 Ma), the retreat of Pacific plate subduction zone resulted in the formation of NW-SE extensional stress field in the north margin of the SCS, NE-striking primary fault of horsetail structure formed; 2) During L. Eocene to E. Oligocene (37.8~28.4 Ma), the change of subduction direction of the Pacific plate and the India-Eurasian collision resulted in the clockwise rotation of extension direction from NW-SE to N-S in the north margin of the SCS, a large amount of EW-striking secondary faults of horsetail structure formed, and the horsetail structure was totally formed in the Weixinan area until this stage.</p>

Download Full-text

“An Outlet to the Western Sea”: Puget Sound, Terraqueous Mobility, and Northern Pacific Railroad’s Pursuit of Trade with Asia, 1864–1892

Western Historical Quarterly ◽

10.1093/whq/whaa114 ◽

2020 ◽

Vol 51 (4) ◽

pp. 439-458

Author(s):

Sean Fraga

Keyword(s):

North American ◽

American West ◽

Puget Sound ◽

North American West ◽

The North ◽

The Pacific ◽

Aqueous Environments ◽

Physical Infrastructure ◽

The Pacific Ocean ◽

Northern Pacific

Abstract The Northern Pacific Railroad saw Puget Sound harbors as environments uniquely suited to connect the North American interior with the Pacific Ocean and enable U.S. trade with East Asia. But in building the physical infrastructure to link transcontinental trains with transpacific ships, Northern Pacific significantly altered Commencement Bay’s shoreline and displaced Puyallups from their traditional territory. The articles uses a terraqueous perspective, emphasizing movement between terrestrial and aqueous environments, to demonstrate how U.S. pursuit of transpacific trade shaped the North American West.

Download Full-text