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1

Interpretation of gravity anomaly to delineate thrust faults locations at the northeastern part of India and its adjacent areas using source edge detection technique, tilt derivative and Cos(θ) analysis

Ghosh Gopal K.

Acta Geophysica

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2019

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Vol. 67, no. 5

1277--1295

EN

The Northeast India and its adjacent areas converge among the three diferent plates, viz. Eurasia, India and Sunda plates. The tectonic interaction of Northeast India and underlying dynamics of the Himalayas as well as the Indo-Burma Ranges might cause the Assam Syntaxis. The area of study is located between latitude 23°–28°N and longitude 88°–96°E and situated in one of the most seismically active tectonic provinces in the world with seismic zone-V. This area had demonstrated several thrust faults activities and tectonic evident accomplishments during the recent past. The complicated geotectonic setups inspirits various smaller magnitude earthquakes, and the current seismicity shows seismic activities are still enduring in the Shillong Plateau, Arakan-Yoma fold belt, Bengal Basin, Naga Hills, Mikir Hills, Upper–Lower Brahmaputra Valley and Mismi Hills of Himalayan foothills. It is imperative to obtain wide-ranging learning tectonic confguration, thrust faults delineation for improved geoscientifc study. Parts of the areas are extremely unreachable, and very limited thrust faults were marked by studying GIS map received from the various agencies and feld geological study. During the past studies, most of the prominent lineaments/thrusts are marked; however, many active and hidden thrust faults are still unidentifed. Seismic data can provide better information about the thrust faults locations, but due to small number of seismic data, the information is not adequate. In this paper, attempt has been made to study and reinterpret the available ground gravity data of northeastern parts of India for understanding thrust fault locations using various applications of gravity derivatives like analytical signal, horizontal gravity gradient, tilt derivative, horizontal tilt angle derivative and Cos(θ) analysis. Source edge detection technique has also been premeditated to categorize thrust fault locations. It is understandable that the low gravity is observed at Assam Valley which contributed sediment accumulations and higher gravity anomaly observed at Shillong Plateau and Bengal Basin containing denser formations. Bouguer gravity data is used after isostatic correction assuming Airy’s isostasy root depth model and frst-order trend removal using least square technique. The derived thrust fault locations from the present study are superimposed with the existing thrust-fault locations for correlation. Some additional thrust faults are narrated which are not previously mapped. It is also suggested that Brahmaputra Thrust, Dauki Fault, Naga Thrust, Disang Thrust and Kopili Fault have key responsibility for high seismicity and tectonic movement causing upliftment and depression that encouraged some anticlockwise rotation in the area.

2

Effects of Local Volume Constraints on Optimal Topologies of Continuums

Cai K., Gao Z.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 9b

133-136

EN

Optimal stiffness design of a structure with local volume constraints on its subdomains is investigated. In practical engineering, a structure may have many subdomains with local volume constraints to meet the multi-function of structure. A new heuristic approach simulating the bone remodelling process is presented to solve such problem. The essentials of the present approach are summarized as follows. Firstly, the topology optimization of structure is equivalent to bone remodelling process. Corresponding to the dead zone in bone remodelling theory, a floating interval of reference strain energy density (SED) is proposed. Secondly, the update of the design variable, i.e. the relative density of a material point, is determined by comparison between the local SED and the current interval of reference SED. Thirdly, to satisfy the global constraints in an optimization problem, the global reference interval changes in simulation. Finally, to satisfy the local volume constraints of subdomains in structure, the same amount of local reference intervals are adopted to modify the update rule of local materials. Numerical examples are employed to demonstrate the effects of the local volume constraints on the optimal topologies of structures.

PL

Zbadano metody optymalnego projektowania system z ograniczeniami lokalnych rozmiarów w subdomenach. Przedstawiono nową metodę heurystyczną symulującą szkielet procesu modelowania w celu rozwiązania tego problemu.

3

GPS observations at quasi-conjugate points under disturbed conditions

Momani M.A., Mohd Ali M.A., Yatim B., Abdullah M., Misran N.

Acta Geophysica

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2008

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Vol. 56, no. 4

1179-1201

EN

The conjugacy effects of the GPS scintillation activities during the geomagnetic storms of October 2003, November 2003 and July 2004 have been investigated at the approximately geomagnetically conjugate stations: Scott Base, Antarctica (SBA) and Resolute Cornwallis Island (RESO) in the high Arctic region. The measurements aim at investigation of the similarities and differences of the scintillation activities occurring at the conjugate points in the polar regions under storm conditions and examine the relationship between the Storm Enhanced Density (SED) and scintillation activity. The measurements of the scintillation activities obtained from total scintillation index during these storm periods at both hemispheres showed asymmetry in the ionospheric scintillation occurrence at the conjugate points. Pronounced scintillation activity was observed at the nightside hemisphere with the total scintillation index higher than at the dayside hemisphere. The results also show that the durations of severe scintillation activity were longer at the nightside hemisphere. The measurements showed that the intense scintillation periods were corresponding to the presence of the SED events where more pronounced SED events were observed over the nightside hemisphere.

4

Możliwości rozpoznawania struktur sedymentacyjnych w cienkoławicowych utworach miocenu zapadliska przedkarpackiego

Stankiewicz B., Stadtmüller M.

Przegląd Geologiczny

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2002

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Vol. 50, nr 3

222-226

PL

Utwory miocenu wschodniej części zapadliska przedkarpackiego cechują się dużym zróżnicowaniem litofacjalnym. Znaczna ich część to utwory cienkoławicowe. Stanowi to znaczący problem przy rozpoznawaniu ich rzeczywistego wykształcenia litofacjalnego z zapisu geofizyki otworowej. Niniejsze opracowanie stanowi propozycję wykorzystania do szczegółowej analizy sedymentologicznej krzywych mikrooporności zapisanych przez sondę SED i akustycznego obrazu ścianek otworu CAST, które oparte są na pomiarach o bardzo dużej rozdzielczości. Przedstawiono przykład określania struktur sedymentacyjnych, cech teksturowych oraz wydzielania granic cienkich warstw na podstawie SED i CAST.

EN

The Miocene deposits of the east part of the Carpathian Foredeep are characterized by lithofacial diversity. The bed thickness varies from a few to a few dozen centimetres. This causes significant problems with a proper interpretation of standard wireline geophysical logs. This study presents a suggestion to using dipmeter resistivity curves and acoustic images CAST to detailed sedimentological analysis. An example of identification of sedimentary structures, textures and thin beds'boundaries with SEDand C AST dala is here presented.