Seismicity and Seismotectonics of the Western Lake Ontario Region

The western Lake Ontario region, a traditionally perceived area of low seismic risk, is densely populated and is home to, among other critical facilities, the nuclear reactors of Pickering and Darlington. These and other characteristics of the region call for improved estimates of seismic hazard. Due to a lack of understanding of the causative geological sources and recurrence characteristics of the reported seismic activity, there is considerable uncertainty regarding estimated ground motion parameters, a fundamental component of seismic hazard assessments. To attempt to improve the definition of the seismic source zones and, consequently, seismic hazard assessments, the hypocentres of about 30 local earthquakes were recomputed. A new data compilation, based on the revised locations or those with the least travel-time residuals, shows that local microearthquakes (ML"3.5) generally occur along, or at the intersection of, prominent aeromagnetic or gravity anomalies. A notable seismicity trend extends in a northeast-southwest direction between Toronto and Hamilton, and is bounded by magnetic lineaments. A major geological structure, the Central Metasedimentary Belt Boundary Zone (CMBBZ), coincides with a strong aeromagnetic anomaly which extends to the northeast into the Western Québec Seismic Zone. This magnetic lineament also extends to the south, across Lake Ontario, to join the Akron (Ohio) magnetic boundary that was associated with several historical earthquakes and with a mb=4.9 earthquake in 1986. Most of the seismic events recorded instrumentally in the 20th century have occurred within a depth range of 5 to 20 km. This observation supports the correlation of local earthquakes with deep geophysical and geological features, suggesting contemporary reactivation of basement structures. This may imply that a more conservative deterministic hazard estimate is needed to verify the probabilistic approach currently used to assess seismic hazard in southern Ontario.Cette région, habituellement perçue comme étant de faible sismicité, est densément peuplée et abrite notamment les réacteurs nucléaires de Pickering et de Darlington. En vue de cela, on doit réévaluer les risques de séismes dans la région. Afin d'améliorer la détermination des sources sismiques et, par là, l'évaluation des risques sismiques, on a recalculé les hypocentres d'une trentaine de séismes locaux. Une nouvelle compilation des données, fondée sur les localisations corrigées ou sur celles comprenant le temps de propagation résiduel le plus court, montre que les microséismes locaux (ML=s3.5) surviennent généralement le long ou à l'intersection d'anomalies gravitaires ou aéromagnétiques prononcées. Une zone sismique appréciable s'étend du nord-est au sud-ouest, entre Toronto et Hamilton, et est bordée par des linéaments magnétiques. Une structure géologique majeure, l'aire limite de la zone métasédimentaire centrale, coïncide avec une forte anomalie aéromagnétique qui s'étend vers le nord-est, dans la zone sismique de l'ouest du Québec. Ce linéament magnétique s'étend aussi vers le sud, à travers le lac Ontario, pour rejoindre la limite magnétique d'Akron (Ohio) qui a été associée à de nombreux séismes connus et à un séisme de mb=4,9, en 1986. La plupart des séismes enregistrés par des instruments au cours du XXe s. se sont produits à des profondeurs de 5 à 20 km. Cette observation établit la corrélation entre les séismes locaux et les données géologiques et géophysiques en profondeur, indiquant ainsi une réactivation contemporaine des structures du socle. Cette conclusion implique qu'une évaluation déterministe plus classique des risques sismiques doit être faite afin de tester l'approche probabiliste actuellement entreprise pour évaluer les risques sismiques dans le sud de l'Ontario.Die westliche Ontario-See-Region, die man gewôhnlich fur eine Region mit niedrigem seismischem Risiko hait, ist dicht besiedelt und beherbergt unter anderen bedenklichen Einrichtungen die Kernkraftwerke von Pickering und Darlington. Dièse sowie andere Charakteristika der Region machen eine Verbesserung der Beurteilung des seismischen Risikos not-wendig. Um die Definition seismischer Ursprungszonen und dadurch die Einschàtzung des seismischen Risikos zu ver-bessern, hat man die Hypozentren von etwa 30 lokalen Erdbeben neu berechnet. Eine neue Datenzusammenstellung, gestùtzt auf korrigierte Lagebestimmungen oder solche mit der geringsten Restverbreitungszeit, zeigt, daB ôrtliche Mikroerdbeben (MLL^3.5) gewôhnlich entlang oder an der Kreuzung von deutlichen Aeromagnetik-oder Gravitations-Anomalien auftreten. Eine beachtliche seismische Zone erstreckt sich von Nordost nach Sùdwest zwischen Toronto und Hamilton und ist durch magne-tische Lineamente begrenzt. Eine bedeu-tende geologische Struktur, der Grenz-bereich des zentralen metasedimentâren Gùrtels, stimmt mit einer deutlichen aero-magnetischen Anomalie ùberein, die sich nach Nordosten in die seismische -Zone von West-Québec erstreckt. Dieses magnetische Lineament erstreckt sich auch nach Sùden, quer durch den Ontario-See und ver-bindet sich mit der magnetischen Grenze von Akron(Ohio), welche mit einigen historis-chen Erdbeben sowie einem mb"=4.9 Erdbeben von 1986 in Verbindung gebracht wurde. Die meisten seismischen Vorkom-men, die im 20. Jahrhundert festgestellt wurden, haben in einer Tiefe zwischen 5 bis 20 km stattgefunden. Dièse Feststellung stùtzt die Korrelationen ôrtlicher Erdbeben mit tiefgelegenen geophysikalischen und geologischen Charakteristika und weist auf eine zeitgenôssische Reaktivierung der Grundstrukturen. Dies kônnte zu dem SchluBB fùhren, daB eine mehr konservative deterministische Risikoeinschàtzung notwendig ist, um die gegenwàrtig gebrauchte Wahrscheinlichkeitsmethode bei der Einschàtzung von seismischen Risiken in Sud-Ontario zu ùberprùfen

The Bedrock Surface of the Western Lake Ontario Region: Evidence of Reactivated Basement Structures?

Lower Paleozoic bedrock strata, in south-central Ontario and the adjacent part of New York State are covered by a thick (100m+) blanket of Pleistocene glacial and interglacial sediments. The form of the buried bedrock surface has been reconstructed from 70,000 waterwell boreholes that extend through the entire Pleistocene cover using GIS data processing techniques. The sub-drift bedrock surface shows linear channels that connect the basins of lakes Huron, Ontario and Erie and which form part of an ancestral mid-continent Great Lake drainage system prior to modification and infilling during successive Pleistocene glaciations. This relict drainage system is cut across Lower Paleozoic carbonates and elastics up to 500 m thick, but the position of several channels is aligned above terrane boundaries, faults and other deep-seated and poorly understood geophysical anomalies in underlying mid-Proterozoic Grenville basement rocks. Other channels are controlled by a dominant northwest and northeast trending regional joint system. A close relationship among deeply seated geophysical lineaments, basement structures and topographic lineaments cut across thick Paleozoic cover strata suggests a history of Phanerozoic reactivation and upward propagation of fractures from the Precambrian basement. Several basement structures and lineaments are seismically active suggesting ongoing neotectonic activity across the 'stable' craton of south-central Ontario.La surface de la roche de fond dans la partie ouest du lac Ontario: indices de réactivation des structures du socle. Les couches géologiques de la roche de fond du Paléozoïque inférieur, dans le centre sud de l'Ontario et la partie adjacente de l'État de New York, sont recouvertes par une grande épaisseur (> 100 m) de sédiments glaciaires et interglaciaires. La forme de la surface de la roche de fond enfouie a été reconstituée à partir de 70 000 puits de sondage qui traversent toute la couverture du Pleistocene. La surface sous les dépôts glaciaires laisse voir des chenaux linéaires qui relient les bassins des lac Hurons, Ontario et Érié et qui forment une partie de l'ancien système de drainage des Grands Lacs. Ce réseau de drainage relique entaille les carbonates du Paléozoïque inférieur et les dépôts détritiques jusqu'à 500 m d'épaisseur, mais l'emplacement de plusieurs chenaux est aligné au-dessus des limites de la formation fissurée, des failles et autres anomalies géophysiques profondes et mal connues du socle grenvillien du Protérozoïque moyen. D'autres chenaux sont sous la dépendance d'un réseau de fractures en grande partie orientées vers le NW et vers le NE. Les fortes relations qui existent entre les linéaments géophysiques profonds, les structures du socle et les linéaments topographiques entaillant l'épaisse couverture paléozoïque laissent entrevoir une réactivation au Phanérozoïque et une propagation ascendante des fractures à partir du socle précambrien. Plusieurs structures et linéaments du socle sont sismiquement actifs signalant ainsi une activité néotectonique continue à travers tout le craton dit stable du centre-sud de l'Ontario.Die Sockelstrata aus dem unteren Palàozoikum im sùdlichen Zentrum von Ontario und dem angrenzenden Teil des Staates New York sind von einer dicken (100 m+) Decke glazialer und interglazialer Pleistozànsedimente ùberlagert. Die Form der vergrabenen Oberflache des Sockels ist mittles 70 000 Brunnenbohrlôchern, die durch die ganze Pleistozândecke hindurch-gehen, rekonstruiert worden. Die Sockeloberglàche unter den glazialen Ablagerungen zeigt lineare Rinnen, welche die Becken des Huron-, Ontario-und Eriesees miteinander verbinden und Teil eines alten halbkontinentalen Drainage-systems der Grofîen Seen bilden. Dieses Reliktdrainagesystem schneidet quer durch die Karbonate des unteren Palàozoikums und die Trùmmergesteine bis zu einer Dicke von 500 m, aber die Position gewisser Rinnen ist oberhalb der Grenzen der gespaltenen Foramation, den Verwerfungen und anderen tiefgelegenen und schlecht verstandenen geophysikalischen Anomalien der darunterliegenden Felsen des Grenville-Unterbaus aus dem mittleren Palàozoikum ausgerichtet. Andere Rinnen werden durch ein régionales Kluftsystem, das vor allem nach Nordwesten und Nordosten ausgerichtet ist, kontrolliert. Eine enge Beziehung zwischen tief gelegenen geophysikalischen Lineamenten, Unterbaustrukturen und topographischen Lineamenten, deuten auf eine Reaktivierung im Phanàrozoikum und eine aufsteigende Verbreitung der Bruche vom Unterbau des Pràkambriums. Mehrere Unterbaustrukturen und Lineamente sind seismisch aktiv und zeigen so eine anhaltende neotektonische Aktivitàt quer durch den als "Stabil" angesehenen Kraton vom sùdlichen Zentrum Ontarios

Hallervorden spatz disease – a rare clinicoradiological diagnosis

Hallervorden Spatz disease, also known as pantothenate kinase associated neuro-degeneration, is a rare, progressive neurological disorder usually seen in first decade of life. It is associated with extrapyramidal effects, dysarthria and dementia. Hallervorden Spatz Disease is also associated with psychiatric symptoms, depression and behavioral changes. Affected patients are disabled predominantly by dystonia. MRI, in later stage of the disease, shows “eye of the tiger’ appearance which is fairly diagnostic of Hallervorden Spatz Disease. Response to drugs is often poor and of limited value to these patients. This report highlights a classical case of Hallervorden Spatz disease that presented as an outpatient with dystonia and psychotic symptoms and was diagnosed on the basis of clinical and radiological evidence

Right coronary artery-to-pulmonary artery fistula, the role of echocardiography

Coronary artery fistula is an uncommon but hemodynamically significant anomaly of the coronary arteries, occurring as an incidental finding in 0.1% to 0.2% of coronary angiograms. Although half of the patients with a coronary artery fistula remain asymptomatic, the other half develops CHF, infective endocarditis, myocardial ischemia, or rupture of an aneurysm. This report is illustrative of the right coronary artery fistula to the right pulmonary artery in a 57-year-old male. The definitive diagnosis was made during transesophageal echocardiography and confirmed at operation

Pulmonary hyalinising granuloma: a rare pulmonary disorder

Pulmonary hyalinising granulomas are rare, noninfectious fibrosclerosing lesions of the lung which can mimic metastatic disease. It was first described in literature by Engleman et al in the year 1977. Its etiology is unknown but they may be caused by an exaggerated immune response. The patient typically presents with cough, chest pain. dyspnoea or haemoptysis in association with multiple bilateral parenchymal nodules. We report the case of a 20 years old male who presented with a 12-month history of worsening dry cough. His plain chest radiograph and subsequent CT scan revealed bilateral pulmonary nodules. A CT guided biopsy of the pulmonary lesions was consistent with Pulmonary Hyalinising Granuloma [PHG]

Factors Controlling the Development of Wine-Glass Forms in the Mountains of the Kurdistan Region, Iraq

The northern and northeastern parts of Iraq are mountainous areas and rugged topography with different erosional and morphological forms; among them are the wine-glass (erosional cirques) forms. They are developed in different shapes, sizes, and depths. In the outlets of the wine-glass forms; usually, alluvial fans are formed. The studied area is characterized by the presence of long and narrow anticlines with NW–SE trend that changes westward to E–W trend. The Cretaceous carbonate rocks form the main carapace of the majority of the mountains; however, locally Paleogene and/or Jurassic rocks form the carapace. In the core, rocks down to Devonian are exposed. In those anticlines where only Cretaceous rocks are exposed, no or very rarely wine-glass forms are developed. This is attributed to the Cretaceous carbonate rocks, which exist in huge thicknesses in many formations, with thickly bedded to massive nature and very hard erosion resisting rocks. Tens of the existing wineglass forms are studied to indicate the factors that control their development, which are the type of exposed rocks, their thicknesses, and hardness. To perform the aim of this study, different satellite imagery with different resolutions was used; besides using GIS technique and field check to improve the acquired date

Factors Controlling the Development of Straight Valleys and Streams in the Kurdistan Region, North and Northeast of Iraq

The Iraqi Kurdistan Region is a mountainous area with relief difference ranging from few hundred meters up to 3000 m, and locally more. Almost all of the mountains form anticlines that have NW–SE trend changing westwards of longitude to E–W. The carapace of the majority of the mountains is built up of Cretaceous rocks; however, some of them are of older rocks. Many of those anticlines are crossed by straight valleys and/or are crossed by streams and rivers which form again straight lines and almost coincide with regional lineaments, usually in N–S or NE–SW trend. The studied straight valleys are controlled, most probably by tectonic factors, therefore, exhibit special topographic forms, like straight lineaments crossing many successive anticlines, and also clear bending in some of the ridges in their crossing points to the valleys and/or streams. This paper aims to determine and discuss the factors that control the development of the straight valleys and/or lineaments. To achieve this aim, remote sensing and GIS techniques were followed, using Landsat, QuickBird images as well as geological maps of different scales, and different published articles

Remote Sensing Based Analysis of Interactions between Tectonics and Landscapes in Rawanduz River, Northeastern Iraq

تعد منطقة الدراسة والتي تقع على طول الحدود الشمالية الشرقية للعراق موقعًا مثاليًا لاختبار فكرة وجود مؤشر للتنبؤ بالنشاط التكتوني النسبي. تُعتبر منطقة الدراسة هذه منطقة مميزة للغاية حيث تشمل ثلاثة أنطقة تكتونية رئيسية (نطاق الطيات العالية , نطاق التراكب ونطاق التصادم زاكروس) ، اضافة الى كونها تمتاز بمعدلات متغيرة من النشاط التكتوني الناتج عن تصادم الصفيحة العربية مع الإيرانية. تهدف هذه الدراسة إلى تسليط الضوء على إمكانية استخدام برامج أنظمة المعلومات في بناء قاعدة بيانات جغرافية مورفومترية لحوض نهر راوندوز، والذي يعد احد الأحواض الرئيسية لنهر الزاب الأكبر باستخدام نموذج الارتفاع الرقمي لبعثة المكوك الراداري (SRTM) ) , بيانات لتقييم حالة تصريف هذا النهر بمساعدة نظم المعلومات الجغرافية (GIS) والاستشعار عن بعد. تم إجراء التحليل المورفومتري لحوض الصرف راوندوز أثناء قياس الجوانب الخطية والمساحية والتضاريس ، كما نقدم عملية جديدة لتقدير النشاط التكتوني النسبي وفقًا لمؤشرات الجيومورفيك المفيدة في تقييم التشكل والطبوغرافيا. تم تحديد 26 حوضًا فرعيًا في حوض نهر رواندوز. تشمل المؤشرات  الجيومورفية المستخدمة ما يلي: عدم تناسق حوض الصرف (Af) ، ونسبة عرض أرض الوادي إلى ارتفاع الوادي (Vf) ، ومؤشر شكل حوض الصرف (Bs) ، ومؤشر تعرج الجبهة الأمامية الجبلية (Smf). يتم تجميع النتائج من التحليل والتعبير عنها كمؤشر للتكتونيات النشطة النسبية (Iat) ، والتي نقسمها إلى أربع فئات من النشاط التكتوني المنخفض نسبيا إلى العالي.             The study area along the northeast border of Iraq is a perfect location to test the notion of an index to predict relative tectonic activity, as well as being considered a very characteristic area as include three main tectonic zones (High Folded Zone, Imbricate Zone and Zagros Suture Zone). This study area has variable rates of active tectonics resulting from the collision of Arabian and Iranian plates. This study aims at highlighting the possibility of information systems programs in building a morphometric geographic database of the Rawanduz River Basin, which is one of the main basins of the Greater Zab River using Shuttle Radar Topographic Mission (SRTM), Digital Elevation Model (DEM 90 m) data to evaluate the drainage condition of this river with the help of Geographical Information Systems (GIS) and Remote Sensing. The morphometric analysis of the Rawanduz drainage basin has been executed during measurement of linear, areal and relief aspects as well as we offer a new process for estimate relative active tectonics according on geomorphic indices useful in evaluating morphology and topography. A total of 26 sub-basins were delineated in the Rawanduz River Basin. Geomorphic indices used include: drainage basin asymmetry (Af), ratio of valley-floor width to valley height (Vf), index of drainage basin shape (Bs), and index of mountain front sinuosity (Smf). Results from the analysis are accumulated and expressed as an index of relative active tectonics (Iat), which we divide into four classes from relatively low to higher tectonic activity