Observations on Regional Variability in Ground-Motion Amplitude from Six Mw ~ 6.0 Earthquakes of the North–South Seismic Zone in China

RésuméAlors que les marques profondes laissées par le système d’écoles résiduelles du Nord canadien refont surface, il est important de poursuivre l’étude des politiques en matière d’éducation en parallèle avec les expériences vécues par les élèves dans des lieux et des contextes d’instruction variés. Dans le cas des Inuits, cette recherche fut incomplète. L’auteure avance qu’il faut approfondir les études sur l’implication du gouvernement fédéral dans les premiers systèmes d’éducation dans les Territoires. Ces travaux devraient prendre en compte les disparités locales et régionales ainsi que les expériences des élèves. En mettant l’accent sur les contradictions et les différents impacts causés par l’éducation dans ces communautés dans le passé, et notamment sur les enseignants sans expérience de la vie nordique, cela permettrait de trouver des manières pour décoloniser l’éducation de nos jours. AbstractAs the widespread and deep impressions left on the Canadian North by the residential school system come to light, it is also important to continue examining educational policies alongside the experiences of students throughout a range of schooling sites and forms. Such research on Inuit schooling has been insufficient. I argue that more detailed educational histories of the federal and early territorial school systems should feature local and regional variability in implementation of policy and in student experience. Illuminating the inconsistent and multifaceted ways education affected communities in the past, particularly for teachers new to the North, serves to illustrate the ways education in the present necessitates decolonizing.

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Grave Goods in Early Medieval Europe: regional variability and decline

Internet Archaeology ◽

10.11141/ia.56.11 ◽

2021 ◽

Author(s):

Emma Brownlee

Keyword(s):

Early Medieval ◽

Regional Variability ◽

Low Countries ◽

The North ◽

General Decline ◽

Medieval Europe ◽

Grave Good ◽

Gis Methods ◽

Individual Choices ◽

Grave Goods

This article analyses the use of grave goods in burials across early medieval Europe and how that use changed over the course of the 6th to 8th centuries CE with the widespread transition to unfurnished burial. It uses data gathered from published cemetery excavation reports from England, France, Germany, Belgium, Switzerland, and the Netherlands. The grave good use in these cemeteries was analysed using GIS methods to visualise regional differences, as well as statistical methods to analyse how grave good use evolved over time in those regions. This analysis revealed clear regional distinctions in grave good use, with England and Alamannia appearing similar, with relatively high levels of grave good use. Meanwhile, parts of Frankia and of Burgundy had considerably lower levels of grave good use. Distributions of individual artefact types tended to match those of overall numbers, but there were a few key exceptions, such as vessels, which followed a quite different pattern, being found in high numbers along the Frankish coast, but in much lower numbers elsewhere. Despite these overall trends, there was still considerable intra-regional and intra-cemetery variation that suggests communities and individuals had the ability to make highly individual choices about the way to bury their dead, along with the ability to subvert local norms. It also revealed that while there was a general decline in the use of grave goods across this period, and everywhere eventually reached the point of almost completely unfurnished burial, this decline occurred at different rates. In particular, there was a zone around the North Sea, including Kent, western Frankia, and the Low Countries, where there was little change in grave good use until it was suddenly abandoned in the early 8th century. Different types of objects declined at different rates across different regions, with few clear trends, suggesting that only personal accessories held a common significance across Europe; the meanings of all other object types were negotiated on a local basis.

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State of stress in central and eastern North American seismic zones

10.26686/wgtn.13792391.v1 ◽

2021 ◽

Author(s):

S Mazzotti ◽

John Townend

Keyword(s):

Local Stress ◽

Seismic Zone ◽

Postglacial Rebound ◽

Long Wavelength ◽

Seismic Zones ◽

The North ◽

State Of Stress ◽

Perturbation Source ◽

Horizontal Compressive Stress ◽

Hb S

We use a Bayesian analysis to determine the state of stress from focal mechanisms in ten seismic zones in central and eastern North America and compare it with regional stress inferred from borehole measurements. Comparisons of the seismologically determined azimuth of the maximum horizontal compressive stress (S HS ) with that determined from boreholes (S HB ) exhibit a bimodal pattern: In four zones, the S HS and regional S HB orientations are closely parallel, whereas in the Charlevoix, Lower St. Lawrence, and Central Virginia zones, the S HS azimuth shows a statistically significant 30°-50° clockwise rotation relative to the regional S HB azimuth. This pattern is exemplified by the northwest and southeast seismicity clusters in Charlevoix, which yield S HS orientations strictly parallel and strongly oblique, respectively, to the regional S HB trend. Similar ~30° clockwise rotations are found for the North Appalachian zone and for the 2003 Bardwell earthquake sequence north of the New Madrid zone. The S HB /S HS rotations occur over 20-100 km in each seismic zone, but they are observed in zones separated by distances of up to 1500 km. A possible mechanism for the stress rotations may be the interaction between a long-wavelength stress perturbation source, such as postglacial rebound, and local stress concentrators, such as low-friction faults. The latter would allow low-magnitude (<10 MPa) postglacial rebound stresses to locally perturb the preexisting stress field in some seismic zones, whereas postglacial rebound stresses have little effect on the intraplate state of stress in general. © 2010 Geological Society of America.

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On the Extraction of Microseismic Ground Motion from Analog Seismograms for the Validation of Ocean-Climate Models

Seismological Research Letters ◽

10.1785/0220190276 ◽

2020 ◽

Vol 91 (3) ◽

pp. 1518-1530 ◽

Cited By ~ 2

Author(s):

Thomas Lecocq ◽

Fabrice Ardhuin ◽

Fabienne Collin ◽

Thierry Camelbeeck

Keyword(s):

Ground Motion ◽

North Sea ◽

Climate Models ◽

North Atlantic Ocean ◽

Wave Model ◽

Ocean Wave ◽

Good News ◽

Flood Event ◽

Ocean Climate ◽

The North

Abstract We report on a pilot demonstration of the usefulness of analog seismograms to improve the database of ocean storms before the 1980s by providing additional data for the quantitative validation of ocean wave modeling, in particular for extreme events. We present a method for automatic digitization of paper seismograms to extract microseismic ground-motion periods and amplitudes. Each minute of the original paper records is scanned and vectorized. The amplitudes are calibrated based on the original metadata taken from official bulletins. The digitized time series is processed to extract power spectral densities, which are compared with modeled microseisms levels computed using a numerical ocean wave model. As a case study, we focus on one month of data recorded at the Royal Observatory of Belgium (ROB) from January to February 1953, around the “Big Flood” event, a tragic storm surge that flooded the lowlands of England, the Netherlands, and Belgium on 1 February 1953. The reconstructed spectrograms for the three components of ground motion show clear storm signatures that we relate to specific sources in the North Atlantic Ocean. However, our models of the Big Flood event based on these data do not result in the expected amplitudes as modeled compared to the observational data when the storm reached its maximum in the southern North Sea. We suggest that the source of microseisms recorded at ROB is related to the primary microseism generated in the North Sea, at periods of 7–8 s. Other discrepancies identified suggest small modifications of the source locations or energy. Reconstructed horizontal and vertical ground motions are coherent. This is a good news for the purpose of present-day analyses of constructing twentieth century ocean-climate models, especially as during much of that time only horizontal seismographs were installed at observatories.

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Regional co-variability of spatial and temporal soil moisture–precipitation coupling in North Africa: an observational perspective

Hydrology and Earth System Sciences ◽

10.5194/hess-22-3275-2018 ◽

2018 ◽

Vol 22 (6) ◽

pp. 3275-3294 ◽

Cited By ~ 2

Author(s):

Irina Y. Petrova ◽

Chiel C. van Heerwaarden ◽

Cathy Hohenegger ◽

Françoise Guichard

Keyword(s):

Soil Moisture ◽

North Africa ◽

Deep Convection ◽

Sensible Heat Flux ◽

Arid Environment ◽

The South ◽

Regional Variability ◽

Convective Systems ◽

The North ◽

Temporal Coupling

Abstract. The magnitude and sign of soil moisture–precipitation coupling (SMPC) is investigated using a probability-based approach and 10 years of daily microwave satellite data across North Africa at a 1∘ horizontal scale. Specifically, the co-existence and co-variability of spatial (i.e. using soil moisture gradients) and temporal (i.e. using soil moisture anomaly) soil moisture effects on afternoon rainfall is explored. The analysis shows that in the semi-arid environment of the Sahel, the negative spatial and the negative temporal coupling relationships do not only co-exist, but are also dependent on one another. Hence, if afternoon rain falls over temporally drier soils, it is likely to be surrounded by a wetter environment. Two regions are identified as SMPC “hot spots”. These are the south-western part of the domain (7–15∘ N, 10∘ W–7∘ E), with the most robust negative SMPC signal, and the South Sudanese region (5–13∘ N, 24–34∘ E). The sign and significance of the coupling in the latter region is found to be largely modulated by the presence of wetlands and is susceptible to the number of long-lived propagating convective systems. The presence of wetlands and an irrigated land area is found to account for about 30 % of strong and significant spatial SMPC in the North African domain. This study provides the first insight into regional variability of SMPC in North Africa, and supports the potential relevance of mechanisms associated with enhanced sensible heat flux and mesoscale variability in surface soil moisture for deep convection development.

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Natural Seismicity in and around the Rome Trough, Eastern Kentucky, from a Temporary Seismic Network

Seismological Research Letters ◽

10.1785/0220190015 ◽

2020 ◽

Vol 91 (3) ◽

pp. 1831-1845 ◽

Cited By ~ 1

Author(s):

N. Seth Carpenter ◽

Andrew S. Holcomb ◽

Edward W. Woolery ◽

Zhenming Wang ◽

John B. Hickman ◽

...

Keyword(s):

New York ◽

Oil And Gas ◽

Seismic Network ◽

Earthquake Activity ◽

Seismic Zone ◽

Injection Wells ◽

Eastern Kentucky ◽

The North ◽

Horizontal Compressive Stress ◽

Natural Seismicity

Abstract The Rome trough is a northeast-trending graben system extending from eastern Kentucky northeastward across West Virginia and Pennsylvania into southern New York. The oil and gas potential of a formation deep in the trough, the Rogersville shale, which is ∼1 km above Precambrian basement, is being tested in eastern Kentucky. Because induced seismicity can occur from fracking formations in close proximity to basement, a temporary seismic network was deployed along the trend of the Rome trough from June 2015 through May 2019 to characterize natural seismicity. Using empirical noise models and theoretical Brune sources, minimum detectable magnitudes, Mmin, were estimated in the study area. The temporary stations reduced Mmin by an estimated 0.3–0.8 magnitude units in the vicinity of wastewater-injection wells and deep oil and gas wells testing the Rogersville shale. The first 3 yr of seismicity detected and located in the study area has been compiled. Consistent with the long-term seismicity patterns in the Advanced National Seismic System Comprehensive Catalog, very few earthquakes occurred in the crust beneath the Rome trough—only three events were recorded—where the temporary network was most sensitive. None of these events appear to have been associated with Rogersville shale oil and gas test wells. Outside of the trough boundary faults, earthquakes are diffusely distributed in zones extending into southern Ohio to the north, and into the eastern Tennessee seismic zone to the south. The orientations of P axes from the seven first-motion focal mechanisms determined in this study are nearly parallel with both the trend of the Rome trough and with the orientation of maximum horizontal compressive stress in the region. This apparent alignment between the regional stress field and the strikes of faults in the trough at seismogenic depths may explain the relative lack of earthquake activity in the trough compared with the surrounding crust to the north and south.

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Formation of the North–South Seismic Zone and Emeishan Large Igneous Province in Central China: Insights from P-Wave Teleseismic Tomography

Bulletin of the Seismological Society of America ◽

10.1785/0120200067 ◽

2020 ◽

Vol 110 (6) ◽

pp. 3064-3076

Author(s):

Chuansong He ◽

M. Santosh

Keyword(s):

High Velocity ◽

Large Scale ◽

P Wave ◽

Large Igneous Province ◽

Seismic Zone ◽

Teleseismic Tomography ◽

Emeishan Large Igneous Province ◽

The North ◽

Igneous Province ◽

Stress Accumulation

ABSTRACT The geodynamic features of the north–south seismic zone (NSSZ) and the formation of the Emeishan large igneous province (ELIP) in China remain controversial. In this study, we conducted detailed P-wave teleseismic tomography studies in the NSSZ and adjacent regions. The results revealed large high-velocity anomalies beneath the Songpan–Ganzi Block and the South China Block, possibly representing large-scale lithospheric delamination. We further identified low-velocity structures at 50–200 km depths in the western and southern parts of the NSSZ, suggesting an upwelling asthenosphere induced by delamination and the absence of a rigid lithosphere. Two high-velocity structures beneath the Sichuan basin and the Alashan block were also revealed, which may represent the lithospheric roots of these structures. These rigid lithospheric roots may have obstructed the eastward extrusion of the Tibetan plateau and led to stress accumulation and release (triggering earthquakes) in the Longmenshan Orogenic Belt and the northern part of the NSSZ. Because of this obstruction, the eastward extrusion was redirected southeastward to Yunnan in the southern part of the NSSZ, which led to stress accumulation and release causing earthquakes along the Honghe and Xiaojiang faults. The results from this study reveal a high-velocity structure with a subducted slab-like appearance that may represent vestiges of the Paleo-Tethys oceanic lithosphere, which subducted beneath the ELIP and initiating large-scale mantle return flow or mantle upwelling, contributing to the formation of the ELIP.

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