Seismotectonic characteristics of the Lower St. Lawrence Seismic Zone, Quebec: insights from geology, magnetics, gravity, and seismics

2003 ◽  
Vol 40 (2) ◽  
pp. 317-336 ◽  
Author(s):  
Maurice Lamontagne ◽  
Pierre Keating ◽  
Serge Perreault
Keyword(s):  
Sedimentary Cover ◽  
Local Stress ◽  
Aerial Photographs ◽  
Normal Faults ◽  
Seismic Zone ◽  
Precambrian Basement ◽  
History Of ◽  
Seismic Reflection Profiles ◽  
East West ◽  
St Lawrence River

The estuary of the St. Lawrence River between Baie-Comeau and Sept-Îles is an area where 50 to 100 earthquakes are detected yearly. This study defines the major lineaments of the Precambrian basement and compares them with mapped faults where possible, and examines their possible correlation with the local earthquakes. Onshore, aerial photographs, remote sensing images, and field mapping are used to identify the geological structures of the Precambrian basement, while offshore, they are interpreted from potential field (magnetic, gravity) and a published synthesis of seismic reflection profiles. The Precambrian basement dips towards the southeast under the Appalachian nappes with normal faults with kilometre-scale throw and east–west or ENE–WSW strikes. Onshore, a system of normal brittle faults with a complex history of movements crosscuts both the Precambrian basement and the overlying Ordovician sedimentary cover. Most earthquakes occur beneath the St. Lawrence River at focal depths between about 7 and 25 km that place them well within the Precambrian Shield. In the Lower St. Lawrence Seismic Zone, the trend of the normal faults that changes from SW–NE to mostly east–west, and lateral density anomalies possibly enhance the local stress level. It is also suggested that local faults could be weak because of crustal fluids at depth, possibly under hydrostatic pressure, or to fault gouge, which leads to a lower coefficient of friction. It is possible that the region was intensely fractured by the emplacement of the Sept-Iles layered igneous complex.

The June 1987 Southeastern Illinois Earthquake: Possible Tectonism Associated with the La Salle Anticlinal Belt

1988 ◽  
Vol 59 (4) ◽  
pp. 151-157 ◽  
Author(s):  
Michael W. Hamburger ◽  
John. A. Rupp
Keyword(s):  
Transition Zone ◽  
Main Shock ◽  
Fault System ◽  
Sharp Change ◽  
Seismic Zone ◽  
Precambrian Basement ◽  
Seismic Reflection Data ◽  
Earthquake Focal Mechanism ◽  
Wabash Valley ◽  
East West

Abstract The June 10, 1987 southeastern Illinois earthquake (mb =5.0) is the largest event to have taken place in the northern midcontinent for 19 years, and is one of only seven events of comparable size to have occurred in this area in the 200-year historical record. The earthquake occurred near a transition zone between the northeast-trending Wabash Valley Fault System and the northwest-trending La Salle flexural belt. The main shock epicenter is positioned 30 km north of the northernmost mapped Wabash Valley faults, and detailed structural mapping in this area documents a systematic decrease in displacement along these faults approaching this termination. Immediately to the northeast of the main shock begins a major northwest-trending late Paleozoic fold structure: the La Salle Anticlinal Belt. This structural feature, marking a major flanking monocline of the Illinois Basin, displays over 750 meters of relief disrupting the lower Paleozoic strata, as well as the Precambrian basement surface. While there is little indication of faulting of the uppermost Paleozoic strata, the sharpness of the relief on the basement and limited seismic reflection data suggest that high-angle basement faulting, down-dropped toward the basin, has occurred beneath the Paleozoic cover. The transition between these two structural regimes may be accompanied by a sharp change in the regional contemporary stress orientation, from east-west compression in northern and central Indiana to north-northeast-trending compression in the Wabash and Ohio River valleys. The earthquake focal mechanism, like that of two other events in the area, indicates a nearly east-west P-axis, paralleling the trend of other contemporary stress indicators. Well constrained depths of aftershocks suggest that the main shock occurred at a depth of 7–11 km, which would place it within the mid-crust, 4–6 km below the top of the Precambrian basement. We propose that the southeastern Illinois event is associated with basement deformation within a complex structural transition zone connecting the two tectonic regimes, rather than the result of reactivation of a simple graben-like extension of the New Madrid Seismic Zone.

scholarly journals THE TECTONIC SETTING OF THE OCTOBER 8 m 2005 EARTHQUAKE IN KASHMIR, NORTH PAKISTAN

2018 ◽  
Vol 40 (1) ◽  
pp. 463
Author(s):  
E. Skourtsos ◽  
E. Lekkas
Keyword(s):  
Sedimentary Cover ◽  
Tectonic Setting ◽  
Hanging Wall ◽  
Focal Depth ◽  
Thrust Fault ◽  
Normal Faults ◽  
Seismic Zone ◽  
Distinct Structure ◽  
Seismic Fault ◽  
Dip Angle

On the 8th of October 2005 an earthquake of magnitude 7.6 occurred in northern Pakistan. The earthquake epicenter was located in Pakistan Kashmir, 90 km north of Islamabad, the capital of Pakistan. The focal depth was 26 km triggered by a thrust fault striking NW-SE and of 40o dip angle towards the NE. The mean fault slip was estimated as 4 m. The aftershocks epicenters were located northeastwards of the Indus - Kohistan Seismic Zone. The structures that trace the activated fault were distributed along the southwestern limb of the Muzaffarabad anticline and grouped as structures of flexural-slip folding, structures that are correlated to folding and normal faults. The latter may represent overturned segments of the seismic fault on the high-angle limb of the Muzaffarrabad anticline. This anticline is located on the hanging wall of a thrust fault with geometry and kinematics characteristics similar to those of the Indus — Kohistan Seismic Zone. This zone, from the Hazara - Kashmir Syntaxis to the Swat River represents a blind thrust under the metamorphosed rocks of the Lower Himalayas, while in the region of Sub- Himalayas becomes a distinct structure. This thrust fault is linked in depth to the Main Himalaya Thrust through which, the cratonic basement of India is subducting under its sedimentary cover.

The evolution of the Malvern Lineament [abstract only]

1986 ◽  
Vol 317 (1539) ◽  
pp. 277-277 ◽  
Keyword(s):  
Seismic Reflection ◽  
Tectonic Activity ◽  
Normal Faults ◽  
Sedimentary Deposits ◽  
Westerly Direction ◽  
History Of ◽  
Early Palaeozoic ◽  
Western Side ◽  
Seismic Reflection Profiles ◽  
Uplift And Erosion

The geology of the Malvern Hills has been the subject of controversy since the 1850s. Many of the problems have now been resolved by using a combination of techniques including mapping, seismic-reflection profiling, deep drilling and geochronology. The Malvern Lineament is a major north-south trending crustal structure with a complex history of tectonic activity. In early Palaeozoic times thrusting on the Malvern axis caused uplift of the area to the east of the axis and some thickening of sedimentary deposits to the west. The importance of the Llandovery unconformity along the western side of the Malvern Hills is stressed. In late Carboniferous times there was major thrusting in a westerly direction, probably associated with dextral transpression, and considerable uplift and erosion of the area to the east of the Malverns. In Permian and Triassic times an extensional lithospheric stress field was initiated. This resulted in reactivation of the earlier thrusts as major normal faults down throwing to the east and with throws, locally, in excess of 2.5 km. These faults, which dip eastwards at between 35 and 50°, are detectable on seismic-reflection profiles to a depth of about 5 km and controlled the development of the Worcester Basin, inverting the site of an older ‘high’.

scholarly journals Inverted Basins by Africa–Eurasia Convergence at the Southern Back-Arc Tyrrhenian Basin

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 117
Author(s):  
Maria Filomena Loreto ◽  
Camilla Palmiotto ◽  
Filippo Muccini ◽  
Valentina Ferrante ◽  
Nevio Zitellini
Keyword(s):  
Seismic Reflection ◽  
Magnetic Data ◽  
Normal Faults ◽  
Sedimentary Sequence ◽  
Initiation Zone ◽  
Arc Setting ◽  
Seismic Reflection Profiles ◽  
Back Arc ◽  
Flower Structures ◽  
Tyrrhenian Basin

The southern part of Tyrrhenian back-arc basin (NW Sicily), formed due to the rifting and spreading processes in back-arc setting, is currently undergoing contractional tectonics. The analysis of seismic reflection profiles integrated with bathymetry, magnetic data and seismicity allowed us to map a widespread contractional tectonics structures, such as positive flower structures, anticlines and inverted normal faults, which deform the sedimentary sequence of the intra-slope basins. Two main tectonic phases have been recognised: (i) a Pliocene extensional phase, active during the opening of the Vavilov Basin, which was responsible for the formation of elongated basins bounded by faulted continental blocks and controlled by the tear of subducting lithosphere; (ii) a contractional phase related to the Africa-Eurasia convergence coeval with the opening of the Marsili Basin during the Quaternary time. The lithospheric tear occurred along the Drepano paleo-STEP (Subduction-Transform-Edge-Propagator) fault, where the upwelling of mantle, intruding the continental crust, formed a ridge. Since Pliocene, most of the contractional deformation has been focused along this ridge, becoming a good candidate for a future subduction initiation zone.

scholarly journals From Print Texts to Online Gaming: The Cross-Cultural History of Wuxia Fictions in Vietnam

SAGE Open ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 215824402110213
Author(s):  
Phan Anh Quang
Keyword(s):  
Cultural History ◽  
Online Games ◽  
Online Gaming ◽  
Cross Cultural ◽  
Business Strategies ◽  
Mobile Gaming ◽  
Life Course Approach ◽  
Cultural Proximity ◽  
History Of ◽  
East West

The popularization of online gaming in Vietnam, including PC and mobile gaming, has witnessed the contribution of wuxia fictions as an essential aspect of digital content production. This article shows an attempt in tracing the cultural history of wuxia works in Vietnam. East-West differences have also been taken into consideration as a way to explain reading and playing preferences. By using life course approach along with the concepts of nostalgia and cultural proximity, this study tries to historically portray the wuxia readership in Vietnam and its vestige found in wuxia online games. The findings indicate that wuxia novels serve as a crucial factor representing the literary relationship between the Sinosphere and Vietnam. Its presence has enriched the content of Vietnamese literature, adding a new genre that has been widely accepted by many generations of Vietnamese readers. Because wuxia online games could be seen as the digital continuation of wuxia fictions, the author argues that prior experience drawn from interacting with wuxia novels affects the game selection-making process of players, and gaming companies in Vietnam also acknowledge that and deploy appropriate business strategies.

Die Bundeswehr und die Belgischen Streitkräfte in Deutschland

2021 ◽  
Author(s):  
Jonas Springer
Keyword(s):  
Local Level ◽  
Military Training ◽  
Armed Forces ◽  
History Of ◽  
Military Training Areas ◽  
The Military ◽  
First Time ◽  
The Relationship ◽  
Peak Phase ◽  
East West

This study is dedicated to the regional history of the East-West conflict on the basis of the relationship between the Germany military and the Belgian armed forces stationed in Germany. The central question it addresses is which factors were largely responsible for the interdependence between actors and institutions of both armies. In addition to analysing the limited time of the peak phase of Belgian military deployment in the Federal Republic 1946–1990, the book concentrates regionally on the military training areas of Vogelsang in the Eifel and the Wahner Heide near Cologne as military contact zones. For this purpose, the author evaluates unpublished archival sources at the local level for the first time.

Rampart seismic zone of central Alaska

1983 ◽  
Vol 73 (3) ◽  
pp. 813-829
Author(s):  
P. Yi-Fa Huang ◽  
N. N. Biswas
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
B Value ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Lithospheric Plate ◽  
Normal Faults ◽  
Seismic Zone ◽  
The West ◽  
Fault Plane Solutions

abstract This paper describes the characteristics of the Rampart seismic zone by means of the aftershock sequence of the Rampart earthquake (ML = 6.8) which occurred in central Alaska on 29 October 1968. The magnitudes of the aftershocks ranged from about 1.6 to 4.4 which yielded a b value of 0.96 ± 0.09. The locations of the aftershocks outline a NNE-SSW trending aftershock zone about 50 km long which coincides with the offset of the Kaltag fault from the Victoria Creek fault. The rupture zone dips steeply (≈80°) to the west and extends from the surface to a depth of about 10 km. Fault plane solutions for a group of selected aftershocks, which occurred over a period of 22 days after the main shock, show simultaneous occurrences of strike-slip and normal faults. A comparison of the trends in seismicity between the neighboring areas shows that the Rampart seismic zone lies outside the area of underthrusting of the lithospheric plate in southcentral and central Alaska. The seismic zone outlined by the aftershock sequence appears to represent the formation of an intraplate fracture caused by regional northwest compression.

Tectonics and recent seismicity near Flathead Lake, Montana

1982 ◽  
Vol 72 (5) ◽  
pp. 1591-1599
Author(s):  
Anthony Qamar ◽  
Jerry Kogan ◽  
Michael C. Stickney
Keyword(s):  
Ice Sheet ◽  
Normal Faults ◽  
Earthquake Swarms ◽  
Flathead Lake ◽  
Glacial Processes ◽  
Cordilleran Ice Sheet ◽  
Large Earthquakes ◽  
East West

abstract Since 1900, more than 290 earthquakes have been reported near Flathead Lake, Montana. Surprisingly, none has exceeded magnitude 5 to 512. Most recent earthquake swarms appear to result from east-west or northwest-southeast extension along short fault segments west and north of the lake. Major normal faults like the Swan and Mission faults east of the lake may pose higher risk, but they appear dormant today. Deformation of sediments in Flathead Lake may be caused by several large earthquakes more than 10,000 years ago but is more probably due to glacial processes accompanying the last retreat of the Cordilleran ice sheet.

scholarly journals EVOLUTION OF KARAKORAM SEQUENCE, HUNZA VALLEY NE PAKISTAN: EVIDENCES FROM FIELD MAPPING AND MICRO-ANALYTICAL WORK

2020 ◽  
Vol 5 ◽  
pp. 19
Author(s):  
S. S. Baig ◽  
C. Xue ◽  
Masroor Alam ◽  
Naeem Ullah ◽  
M. Alam ◽  
...  
Keyword(s):  
Geological Mapping ◽  
Central Portion ◽  
High Grade ◽  
Metamorphic Complex ◽  
Field Mapping ◽  
The North ◽  
Analytical Work ◽  
History Of ◽  
Micro Analysis ◽  
East West

The Karakoram metamorphic Complex (KMC) in the southern Karakoram block is one of the best examples of Barrovian type metamorphism that comprises numerous exhumed metapelite units where a series of low to high grade (green schist to sillimanite facie) rocks are exposed. This sequence shows a complex polyphase history of metamorphism and deformation which offer deeper understanding of collision orogeny. Karakoram metamorphic Complex contains metapelites, meta-carbonates, meta-igneous and amphibolite layers, cross-cut by granite sheets in the northern part. This complex is bounded to the north by the Hunza plutonic unit which is the central portion of the massive east-west trending Karakoram axial batholith and to the southwest by the Main Karakoram thrust (MKT). In this contribution, we provide detail geological mapping, petrography, geochemistry and micro-analytical work using Electron Prob-micro analysis in the central Hunza Valley.

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