Detections of Directional Dynamic Triggering in Intraplate Regions of the United States

2021 ◽  
Author(s):  
Vivian Tang ◽  
Kevin Chao ◽  
Suzan van der Lee
Keyword(s):  
United States ◽  
Surface Waves ◽  
Seismic Activity ◽  
Active Regions ◽  
The United States ◽  
North American Plate ◽  
Western Boundary ◽  
Eastern United States ◽  
Dynamic Triggering ◽  
The North

ABSTRACT We report tremor or local earthquake signals that occurred during the propagation of Love and Rayleigh waves from the 2012 Mw 8.6 Sumatra earthquake in three intraplate regions: Yellowstone, central Utah, and Raton basin (Colorado). These surface waves likely also dynamically triggered seismic activity along the western boundary of the North American plate, and did not trigger seismic activity in the central and eastern United States. We report additional potential dynamic triggering in the three aforementioned intraplate regions by surface waves from 37 additional large earthquakes, recorded between 2004 and 2017. These surface waves’ transient stresses generally appear to trigger tremor in seismically, volcanically, and hydrothermally active regions, such as Yellowstone, if the waves also arrive from favorable directions. These stresses do not appear to be decisive factors for triggering local earthquakes reported for the Raton basin and central Utah, whereas, surface waves’ incidence angles do appear to be important there.

Effects of temporal variations in seismicity on seismic hazard

1981 ◽  
Vol 71 (1) ◽  
pp. 321-334
Author(s):  
Robin K. McGuire ◽  
Theodore P. Barnhard
Keyword(s):  
United States ◽  
Seismic Hazard ◽  
Seismic Activity ◽  
Time Window ◽  
Hazard Analysis ◽  
The United States ◽  
Temporal Variations ◽  
Seismogenic Zone ◽  
Eastern United States ◽  
Ground Shaking

abstract The accuracy of stationary mathematical models of seismicity for calculating probabilities of damaging shaking is examined using the history of earthquakes in China from 1350 A.D. to 1949 A.D. During this time, rates of seismic activity varied periodically by a factor of 10. Probabilities of damaging shaking are calculated in 62 cities in North China using 50 yr of earthquake data to estimate seismicity parameters; the probabilities are compared to statistics of damaging shaking in the same cities for 50 yr following the data window. These comparisons indicate that the seismic hazard analysis is accurate if: (1) the maximum possible earthquake size in each seismogenic zone is determined from the entire seismic history rather than from a short-time window; and (2) the future seismic activity can be estimated accurately. The first condition emphasizes the importance of realistically estimating the maximum possible size of earthquakes on faults. The second indicates the need to understand possible trends in seismic activity where these exist, or to develop an earthquake prediction capability with which to estimate future activity. Without the capability of estimating future seismicity, stationary models provide less accurate but generally conservative indications of seismic ground-shaking hazard. In the United States, the available earthquake history is brief but gives no indication of changing rates of activity. The rate of seismic strain release in the Central and Eastern United States has been constant over the last 180 yr, and the geological record of earthquakes on the southern San Andreas Fault indicates no temporal trend for large shocks over the last 15 centuries. Both observations imply that seismic activity is either stationary or of such a long period that it may be treated as stationary for seismic hazard analyses in the United States.

scholarly journals The recent development of melanism in the larvæ of certain species of Lepidoptera, with an account of its inheritance in Selenia bilunaria esp

1932 ◽  
Vol 111 (770) ◽  
pp. 188-200 ◽  
Keyword(s):  
United States ◽  
Central Europe ◽  
The United States ◽  
Eastern United States ◽  
Evolutionary Processes ◽  
Number Of Species ◽  
The North ◽  
North Eastern ◽  
Geometrid Moth ◽  
State Of Affairs

One of the most remarkable evolutionary processes, the more striking since it has occured before our eyes, has been the rise and spread of melanism and melanochroism amongst the Lepidopetera. Commencing about 1850 in the Manchester area in England with the Geometrid moth Amphidasys betularia L., which yielded the black form carbonaria Jord. ( doubledayaria Mill.), this development has proceeded so rapidly, and become so widespread, that now there is scarcely a country in Northern and Central Europe which does not produce its quota of melanic insects. Moreover, the same state of affairs exists in the North-Eastern United States, although there the number of species affected, up to the present, is not so great as in Europe. Another important feature about these changes lies in the circumstance that, almost uniformly, in Europe and in the United States, the first species to exhibit melanism in any given area have been Amphidasys betularia and Tephrosia crepuscularia . From the beginning, the Geometridæ, more especially the subfamily Boarmiinæ, have provided not only the bulk of the melanic varieties, but also the greatest numbers of individuals. In many areas, as for example in the case of A. betularia and Y psipetes trifasciata , only black examples occur. Nevertheless, other groups include species which have gone black; for instance, the Noctuidæ present black forms of Aplecta nebulosa Hufn., the Cymatophoridæ of Cymatophora or F., the Arctiidæ of Spilosoma lubricipeda L., the Gelechiidæ of Chimabacche fagella F., and so on.

scholarly journals An Examination of Precipitation in Observations and Model Forecasts during NAME with Emphasis on the Diurnal Cycle

2007 ◽  
Vol 20 (9) ◽  
pp. 1680-1692 ◽  
Author(s):  
John E. Janowiak ◽  
Valery J. Dagostaro ◽  
Vernon E. Kousky ◽  
Robert J. Joyce
Keyword(s):  
United States ◽  
Diurnal Cycle ◽  
Prediction Models ◽  
Numerical Models ◽  
The United States ◽  
Rain Gauge ◽  
North American Monsoon ◽  
Eastern United States ◽  
Direct Evaluation ◽  
The North

Abstract Summertime rainfall over the United States and Mexico is examined and is compared with forecasts from operational numerical prediction models. In particular, the distribution of rainfall amounts is examined and the diurnal cycle of rainfall is investigated and compared with the model forecasts. This study focuses on a 35-day period (12 July–15 August 2004) that occurred amid the North American Monsoon Experiment (NAME) field campaign. Three-hour precipitation forecasts from the numerical models were validated against satellite-derived estimates of rainfall that were adjusted by daily rain gauge data to remove bias from the remotely sensed estimates. The model forecasts that are evaluated are for the 36–60-h period after the model initial run time so that the effects of updated observational data are reduced substantially and a more direct evaluation of the model precipitation parameterization can be accomplished. The main findings of this study show that the effective spatial resolution of the model-generated precipitation is considerably more coarse than the native model resolution. On a national scale, the models overforecast the frequency of rainfall events in the 1–75 mm day−1 range and underforecast heavy events (>85 mm day−1). The models also have a diurnal cycle that peaks 3–6 h earlier than is observed over portions of the eastern United States and the NAME tier-1 region. Time series and harmonic analysis are used to identify where the models perform well and poorly in characterizing the amplitude and phase of the diurnal cycle of precipitation.

Breakouts in Alberta and stress in the North American plate

1983 ◽  
Vol 20 (9) ◽  
pp. 1445-1455 ◽  
Author(s):  
C. K. Fordjor ◽  
J. S. Bell ◽  
D. I. Gough
Keyword(s):  
United States ◽  
North American ◽  
Horizontal Stress ◽  
The United States ◽  
Oil Wells ◽  
North American Plate ◽  
Mantle Flow ◽  
Orientation Data ◽  
The North ◽  
Canadian Basin

The paper reports a detailed statistical study of breakout azimuths in 48 oil wells widely distributed in the Alberta sedimentary basin, bringing the number of oil wells contributing azimuths to 94 for the western Canadian basin. The azimuths show significant regional variation between the northern, central, and southern parts of the basin. Twenty-one wells, in which breakouts cover depth ranges greater than 600 m, were used to investigate regression of breakout azimuths on depth. Ten wells give positive regression coefficients, 11 are negative, and no coefficient is significant at 95% confidence level. If the dominant northwest–southeast orientation of the long axes of breakouts gives the orientation of the lesser horizontal principal stress Sh, following the hypothesis of Bell and Gough, the inferred stress orientations indicate that throughout the whole basin the direction of the maximum horizontal stress SH is northeast–southwest. Stress measurements, by strain-relief techniques in a mine and from hydraulic fracture in wells, support the stress orientation given by the breakouts. The insignificant regression of breakout azimuths on depth supports the view that the orientation data represent stress in the lithosphere rather than in the sediments only. Directions of the lesser horizontal compression Sh, from Zoback and Zoback in the United States and from breakout studies in western Canada, are combined to suggest that the Mid-Continent stress province of North America may include the western Canadian basin and the Canadian Shield as well as the central United States. Coherent stress with the observed orientation, over the continent east of the Rocky Mountains, would result from northeastward basal drag on the North American plate, as Zoback and Zoback have pointed out. Basal drag to the northeast could arise either if the plate were sliding southwestward over a passive asthenosphere, as suggested by Zoback and Zoback, or if northeastward mantle flow were driving the asthenosphere and the plate northeastward.

Mitigating Impacts of Natural Hazards on Fishery Ecosystems

2008 ◽  
Keyword(s):  
United States ◽  
Natural Hazards ◽  
Fish Habitat ◽  
The United States ◽  
North American Plate ◽  
Fishing Communities ◽  
Plate Boundaries ◽  
Earthquake Hazards ◽  
The North ◽  
The Pacific

<em>Abstract.</em>—Fish and fishing communities are iconic symbols of Alaska. Volcanoes, earthquakes, and tsunamis also stand out as processes that define or shape the Alaska landscape. Alaska has numerous fishing ports that regularly rank in the top 10 ports for commercial landings by weight and value in the United States. In addition to commercial fisheries, subsistence fisheries and sport fishing play an important role in the economy and culture of Alaska. Alaska is home to one of the most active plate boundaries on the planet, where the Pacific Plate is subducting the North American Plate at rates greater than 5 cm/year. This process brings to Alaska earthquakes, tsunamis, and volcanic eruptions. Active plate boundaries around the Pacific basin also make Alaska vulnerable to transoceanic tsunamis generated by earthquakes thousands of miles away. Alaska is the most seismically active state in the United States by a large margin and one of the most active areas in the world. In this paper, we examine the distribution of fishing communities and fish habitat with respect to volcanic and earthquake hazards and discuss the possible implications of these natural hazards to fisheries. Because natural hazards cannot be prevented, communities must prepare for and minimize risk associated with such events. Understanding the nature and distribution of natural hazards is the first step in preparing for future events and limiting the impacts of those events.

scholarly journals The vascular flora of Choctaw County, Mississippi, U.S.A.

2019 ◽  
Vol 13 (1) ◽  
pp. 319-348
Author(s):  
Kevin D. Philley
Keyword(s):  
United States ◽  
Plant Communities ◽  
Vascular Plant ◽  
The United States ◽  
The State ◽  
Eastern United States ◽  
Central Plateau ◽  
Vascular Flora ◽  
Floristic Survey ◽  
The North

The state of Mississippi is one of the least botanically explored areas in the eastern United States. A floristic survey of Choctaw County, Mississippi, was conducted from November 2009 through November 2017 in order to document the vascular flora and describe its plant communities. The county is located in the central portion of the state within the North Central Plateau physiographic region, an area dominated by dissected uplands with acidic to circumneutral sandy-clay soils. Three major river basins occur in the county, including the Big Black River, Noxubee River, and Pearl River. A total of 950 vascular plant species (958 taxa including varieties, subspecies, and recognized hybrids) was recorded. Three-hundred thirteen of these taxa were new county records. Twenty-eight species of special concern as designated by the Mississippi Natural Heritage Program were documented. Approximately 15 percent of the flora is considered non-native to the United States. Eight primary plant communities are also described.

scholarly journals The experience of guestworkers at a United States tourist resort

2013 ◽  
Vol 10 (2) ◽  
pp. 198-228
Author(s):  
Guilherme Mansur Dias
Keyword(s):  
United States ◽  
The United States ◽  
Temporary Employment ◽  
Eastern United States ◽  
Labour Relations ◽  
The North ◽  
North Eastern ◽  
The Us ◽  
Ethnographic Analysis

This article examines temporary employment among foreign workers at the Okemo Mountain Resort, a tourist ski complex located in Vermont state in the north-eastern United States. I discuss the meanings associated with the international displacement of these workers, focusing especially on the ideas and imagery surrounding 'mobility', 'work,' 'travel' and 'youth.' By describing their experiences, along with the practices and discourses of the employer and the US State, the case study shows how Okemo's strategy of hiring a flexible foreign workforce is connected to the multiple meanings through which these groups represent their experience of temporary migration to the United States in the context of increasingly precarious labour relations. The ethnographic analysis proposed by the research provides a counterpoint to the 'macro-analytical' approach employed by most studies on the issue of foreign temporary work in the United States.

Precipitation Distribution Associated with Landfalling Tropical Cyclones over the Eastern United States

2007 ◽  
Vol 135 (6) ◽  
pp. 2185-2206 ◽  
Author(s):  
Eyad Atallah ◽  
Lance F. Bosart ◽  
Anantha R. Aiyyer
Keyword(s):  
United States ◽  
Tropical Cyclones ◽  
Potential Vorticity ◽  
Diabatic Heating ◽  
The United States ◽  
Eastern United States ◽  
Precipitation Distribution ◽  
Thermal Wind ◽  
The North ◽  
The Right

Abstract Tropical cyclones (TCs) making landfall over the United States are examined by separating those associated with precipitation predominantly left of their tracks from those with the same to the right of their tracks. Composites of atmospheric variables for these two TC categories are performed and analyzed using potential vorticity (PV) and quasigeostrophic (QG) frameworks. Dynamical signatures are retrieved from these composites to help understand the evolution of precipitation in these storms. Results indicate that a left of track precipitation distribution (e.g., Floyd 1999) is characteristic of TCs undergoing extratropical transition (ET). In these cases, a positively tilted midlatitude trough approaches the TC from the northwest, shifting precipitation to the north-northwest of the TC. Potential vorticity redistribution through diabatic heating leads to enhanced ridging over and downstream of the TC, resulting in an increase in the cyclonic advection of vorticity by the thermal wind over the transitioning TC. A right of track precipitation distribution is characteristic of TCs interacting with a downstream ridge (e.g., David 1979). When the downstream ridge amplifies in response to TC-induced diabatic heating ahead of a weak midlatitude trough, the PV gradient between the TC and the downstream ridge is accentuated, producing a region of enhanced positive PV advection (and cyclonic vorticity advection by the thermal wind) over the TC. The diabatic enhancement of the downstream ridge is instrumental in the redistribution of precipitation about the transitioning TCs in both cases and poses a significant forecast challenge.

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