Turning waves and crustal reflection profiling

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 335-341 ◽  
Author(s):  
Ralf Stadtlander ◽  
Larry Brown
Keyword(s):  
Sedimentary Cover ◽  
Indirect Evidence ◽  
Sedimentary Environments ◽  
The Past ◽  
Velocity Gradients ◽  
Basement Structures ◽  
Wave Migration ◽  
Seismic Reflection Profiles ◽  
Imaging Algorithms ◽  
Crustal Reflection

In the past, steeply dipping features were often recognized on seismic reflection profiles only from indirect evidence such as vertical offsets of cross‐cutting structures. New imaging algorithms, as for example, turning wave migration have had dramatic success in delineating steep, even‐overturned reflectors in sedimentary environments. Evaluation of the applicability of this technology to deep seismic recordings indicates that steep‐dip and turning wave migration will have limited practicality, generally, in the imaging of basement features because of the weak velocity gradients involved and the corollary requirement for large recording offsets. A potential exception arises when the basement structures to be imaged lie beneath a significant thickness of relatively young (i.e., steep velocity gradient) sedimentary cover.

scholarly journals Navigare necesse est, vivere non est necesse: razmišljanja o prapovijesnoj plovidbi Mediteranom i Jadranom

2017 ◽  
Vol 9 (1) ◽  
Author(s):  
Marcel Burić ◽  
Tihomila Težak Gregl
Keyword(s):  
Indirect Evidence ◽  
Late Neolithic ◽  
Aeolian Islands ◽  
The Past ◽  
The Mediterranean ◽  
Specific Part

In the past fifteen years we have substantially improved our knowledge of the seafaring expeditions in the Mediterranean, based either on the indirect evidence of the navigation or on what we know about the earliest such ventures. This paper presents an overview of what is known about the earliest navigation in the Mediterranean and considers the origin of the first such ventures in the Adriatic as a specific part of the Mediterranean. It focuses on the problem of the navigation between the Italic and Croatian coasts, tackling the possibility of such maritime expeditions based on the distribution of the obsidian from the Aeolian Islands. It also ponders on the practical aspects of the use of sailing vessels in the Late Neolithic. 

An Aerobic Walking Program to Promote Physical Fitness in Older Blind Adults

1985 ◽  
Vol 79 (3) ◽  
pp. 97-99 ◽  
Author(s):  
Donald Mark Weitzman
Keyword(s):  
Physical Fitness ◽  
Critical Role ◽  
Indirect Evidence ◽  
Well Being ◽  
Fitness Program ◽  
Fast Walking ◽  
The Past ◽  
Walking Program ◽  
Group Fitness

Both direct and indirect evidence gathered over the past 40 years strongly suggest that personal exercise can play a critical role in one's emotional and physical well-being. This article describes a unique group fitness program that combines Fast walking with safe calisthenics. The program is especially suitable for older blind adults who get very little healthful exercise and experience considerable depression.

scholarly journals The seismogenic fault system of the 2017 <i>M<sub>w</sub></i> 7.3 Iran-Iraq earthquake: constraints from surface and subsurface data, cross-section balancing and restoration

2018 ◽  
Author(s):  
Stefano Tavani ◽  
Mariano Parente ◽  
Francesco Puzone ◽  
Amerigo Corradetti ◽  
Gholamreza Gharabeigli ◽  
...  
Keyword(s):  
Cross Section ◽  
Sedimentary Cover ◽  
Active Faults ◽  
Fault System ◽  
Limited Information ◽  
Seismogenic Fault ◽  
Plate Convergence ◽  
Mountain Front ◽  
Seismogenic Structures ◽  
Seismic Reflection Profiles

Abstract. The 2017 Mw Iran-Iraq earthquake occurred in a region where the pattern of major plate convergence is well constrained, but limited information is available on the seismogenic structures. Geological observations, interpretation of seismic reflection profiles, and well data are used in this paper to build a regional balanced cross-section that provides a comprehensive picture of the geometry and dimensional parameters of active faults in the hypocentral area. Our results indicate: (i) coexistence of thin- and thick-skinned thrusting, (ii) reactivation of inherited structures, and (iii) occurrence of weak units promoting heterogeneous deformation within the Paleo-Cenozoic sedimentary cover and partial decoupling from the underlying basement. According to our study, the main shock of the November 2017 seismic sequence is located within the basement, along the low-angle Mountain Front Fault. Aftershocks unzipped the up-dip portion of the same fault. This merges with a detachment level located at the base of the Paleozoic succession, to form a crustal-scale fault-bend anticline. Size and geometry of the Mountain Front Fault are consistent with a down-dip rupture width of 30 km, which is required for an Mw 7.3 earthquake.

scholarly journals Late Quaternary Paleoceanography and Sedimentary Environments in Hudson Strait

2007 ◽  
Vol 43 (2) ◽  
pp. 161-178 ◽  
Author(s):  
G. Vilks ◽  
B. MacLean ◽  
B. Deonarine ◽  
C. G. Currie ◽  
K. Moran
Keyword(s):  
Late Quaternary ◽  
Tidal Mixing ◽  
Last Deglaciation ◽  
Eastern Basin ◽  
Sedimentary Environments ◽  
Minimum Age ◽  
Bottom Waters ◽  
Salinity Difference ◽  
Seismic Reflection Profiles ◽  
Glaciomarine Sediments

ABSTRACT Airgun and high resolution Huntec seismic reflection profiles are interpreted to show up to 130 m of glacial, glaciomarine and postglacial sediments overlying bedrock. In a basin at the eastern entrance to Hudson Strait most of the surficial sediment was deposited during the last déglaciation, but in western Hudson Strait multiple till sequences from previous glaciations are recognized. Five acoustic units were identified, at least three of which were penetrated with piston cores. Foraminifera of the stratigraphically deepest core in the eastern basin indicate a proximal glaciomarine environment and a likely presence of an ice shelf. A 14C date of 8060 ± 70 yBP (TO 750) on molluscan shells gives a minimum age for the top of the acoustically laminated distal glaciomarine sediments. The early postglacial foraminifera suggest a period of increased influence of offshore bottom waters restricted to the deep eastern basin. The surface sediments of all cores contain species indigenous of colder and fresher inshore waters of the present time. The ratio of 18CV16O in the benthic foraminifer Cibicides lobatulus is herein related to bottom salinity. Downcore measurements of 8'8O on C. lobatulus tests indicate bottom paleosalinities lower by about 0.5%o shortly before the dated horizon of 8000 yBP. By this time Hudson Strait was sufficiently clear of glacial ice for establishment of the present tidal regime. The lower bottom salinities indicate that tidal mixing took place between glacial meltwater leaving Hudson Bay and the offshore counterflow. This process is thought to have reduced the sharpness of the salinity difference between the offshore water and the surface plume of Laurentide meltwater as it entered the ocean.

Conceptual model of basement deformation beneath the Southern Atlassic front of Tunisia from gravity modeling, seismic reflection profiles and seismotectonic data

2021 ◽  
Author(s):  
Nesrine Frifita ◽  
Mohamed Gharbi ◽  
Kevin Mickus
Keyword(s):  
Seismic Reflection ◽  
Geological Mapping ◽  
Gravity Modeling ◽  
Basement Faults ◽  
Geophysical Study ◽  
Half Graben ◽  
Basement Structures ◽  
Tectonic Style ◽  
Basement Deformation ◽  
Seismic Reflection Profiles

&lt;p&gt;The nature of the basement beneath the Southern Atlassic front of Tunisia is relatively unknown. To study the basement, a geophysical study was undertaken using gravity, seismic reflection and seismicity data. Additionally, these data were used to determine the relationship and the tectonic environment between the known seismicity and basement structures under the Chotts fold belt and the surrounding basins. Based on 2.5D gravity modeling, 2D seismic reflection profiles and known geological mapping, the geometry of the basement was modeled as consisting of horsts,grabens and half-grabens. Specifically, the Sidi Mansour and El-Fejej basins are located on basement uplifts. The variations in the depths of the known earthquakes reveal that the deepest events occurred on basement faults beneath the Metlaoui and Sidi Mansour basins. While the surrounding anticlines within the northern Chotts range are probably inverted into graben and half-graben structures by both thin- and thick-skinned tectonic events. The geophysical findings indicate that the geometry of the basement to consist of a series of uplifted and downdropped regions, where the depth to basement increases from south to north and from east to west. This basement structure can explain the concentration of earthquakes in the northwestern portion of the study area by linking a reactivation of pre-existing east trending fault systems that formed during Alpine Orogeny. The results provide a coherent model showed a mixed thick and thin-skinned tectonic style was active within the study area.&amp;#160;&lt;/p&gt;

Multi-phase reactivations and inversions of Paleozoic–Mesozoic extensional basins during the Wilson cycle: case studies from the North Sea (UK) and the Northern Apennines (Italy)

2019 ◽  
Vol 470 (1) ◽  
pp. 205-243 ◽  
Author(s):  
Vittorio Scisciani ◽  
Stefano Patruno ◽  
Enrico Tavarnelli ◽  
Fernando Calamita ◽  
Paolo Pace ◽  
...  
Keyword(s):  
North Sea ◽  
Sedimentary Cover ◽  
Structural Evolution ◽  
The North ◽  
Structural Framework ◽  
Field Evidence ◽  
The North Sea ◽  
Wilson Cycle ◽  
Basement Structures ◽  
Multi Phase

AbstractThe Caledonian and Variscan orogens in northern Europe and the Alpine-age Apennine range in Italy are classic examples of thrust belts that were developed at the expense of formerly rifted, passive continental margins that subsequently experienced various degrees of post-orogenic collapse and extension. The outer zones of orogenic belts, and their adjoining foreland domains and regions, where the effects of superposed deformations are mild to very mild make it possible to recognize and separate structures produced at different times and to correctly establish their chronology and relationships. In this paper we integrate subsurface data (2D and 3D seismic reflection and well logs), mainly from the North Sea, and structural field evidence, mainly from the Apennines, with the aim of reconstructing and refining the structural evolution of these two provinces which, in spite of their different ages and present-day structural framework, share repeated pulses of alternating extension and compression. The main outcome of this investigation is that in both scenarios, during repeated episodes of inversion that are a characteristic feature of the Wilson cycle, inherited basement structures were effective in controlling stress localization along faults affecting younger sedimentary cover rocks.

Social and non-social knowledge in vervet monkeys

1985 ◽  
Vol 308 (1135) ◽  
pp. 187-201 ◽  
Keyword(s):  
Social Interactions ◽  
Local Population ◽  
Indirect Evidence ◽  
Social Knowledge ◽  
Vervet Monkeys ◽  
East African ◽  
Dominance Relations ◽  
The Past ◽  
The Social ◽  
Ecological Problems

The social knowledge of East African vervet monkeys is striking. W ithin a local population the monkeys recognize individuals, and associate each individual with its particular group. W ithin groups, the monkeys recognize dominance relations, rank orders, and matrilineal kinship, and they remember who has behaved affinitively towards them in the past. Outside the social domain, however, vervets appear to know surprisingly little about other aspects of their environment. Although they do distinguish the different alarm calls given by birds, vervets do not seem to recognize the fresh tracks of a python, or indirect evidence that a leopard is nearby. Similarly, although cooperation and reciprocity seem common in social interactions, comparable behaviour has apparently not evolved to deal with ecological problems. Results support the view that primate intelligence has evolved mainly to solve social problems. As a result, vervet monkeys make excellent primatologists but poor naturalists.

scholarly journals Does Exposure to Analgesics in Utero Cause Schizophrenia?

2005 ◽  
Vol 10 (3) ◽  
pp. 129-130
Author(s):  
Richard L O’Reilly
Keyword(s):  
Genetic Regulation ◽  
Adult Life ◽  
Monozygotic Twins ◽  
Indirect Evidence ◽  
The Past ◽  
The Face ◽  
Early Adult Life ◽  
Environmental Contribution ◽  
Minor Physical Anomalies ◽  
Past Theory

The cause of schizophrenia, a serious mental illness characterized by hallucinations, delusions and a marked deterioration in social functioning, is an enigma that continues to perplex the scientific community. While we know that approximately 80% of the risk of developing schizophrenia is conferred by genes (1), no research group has yet located a gene(s) contributing to the cause of schizophrenia. Moreover, while a significant environmental contribution is indicated by the fact that one-half of monozygotic twins pairs are discordant for schizophrenia, the nature of this environmental contribution is still controversial. The past theory that an abnormal family upbringing was the causative environmental factor has not stood up to scientific scrutiny. In recent years, the search for causative environmental factors has focused on the possibility that some type of prenatal insult predisposes the fetus to develop schizophrenia in early adult life. The initial suspicion of an intrauterine insult was based on indirect evidence. First, dermatoglyphic patterns in patients with schizophrenia were noted to be abnormal. The dermal ridges are laid down between the third and fifth month of gestation, in effect leaving a fossilized record of neurodevelopmental perturbation. Second, minor physical anomalies, typically involving the mouth, ears and eyes, occur with increased frequency in schizophrenia. Much like dermatoglyphic abnormalities, minor physical anomalies represent a disruption of the final phase of the developmental shaping of the face, which takes place in the second trimester. Of course, both abnormal dermatoglyphic patterns and minor physical anomalies may reflect the effects of abnormal genetic regulation of development rather than an extrinsic insult.

The Methodology of Historical Climate Reconstruction and its Application to Africa

1979 ◽  
Vol 20 (1) ◽  
pp. 31-49 ◽  
Author(s):  
Sharon E. Nicholson
Keyword(s):  
Arid Regions ◽  
Indirect Evidence ◽  
The Other ◽  
Short Term ◽  
The Past ◽  
Droughts And Floods ◽  
The Mean ◽  
The One ◽  
Semi Arid ◽  
Past Millennium

This article deals with climatic reconstruction over a period of centuries, on the basis of indirect evidence found in historical and geographical sources. Histories, archives, local chronicles and journals of travellers and settlers contain references to lakes, landscapes, famines, droughts and floods, as well as occasional descriptions of climate and meteorological measurements. Such information can be combined with evidence from geology, palynology or the study of tree-rings to support hypotheses regarding climate and environment several centuries ago.This methodology is here described and used to reconstruct the trend of rainfall fluctuation in Africa over the past millennium. Two approaches are considered: the one seeks to determine absolute variation (thus assessing whether particular episodes were wetter or drier than today); the other focuses on short-term climatic anomalies (e.g. droughts) in which rainfall differed from the mean prevailing at the time, without seeking to relate them to present conditions.The results obtained from this study suggest that during the past millennium there have been two periods of relatively wet conditions in the semi-arid regions south of the Sahara: between the eighth and fourteenth centuries, and between the sixteenth and eighteenth centuries. Evidence for these episodes, and for synchronous fluctuations elsewhere in Africa is presented in the text.

scholarly journals The seismogenic fault system of the 2017 <i>M</i><sub>w</sub> 7.3 Iran–Iraq earthquake: constraints from surface and subsurface data, cross-section balancing, and restoration

Solid Earth ◽  
2018 ◽  
Vol 9 (3) ◽  
pp. 821-831 ◽  
Author(s):  
Stefano Tavani ◽  
Mariano Parente ◽  
Francesco Puzone ◽  
Amerigo Corradetti ◽  
Gholamreza Gharabeigli ◽  
...  
Keyword(s):  
Cross Section ◽  
Sedimentary Cover ◽  
Active Faults ◽  
Fault System ◽  
Limited Information ◽  
Seismogenic Fault ◽  
Plate Convergence ◽  
Mountain Front ◽  
Seismogenic Structures ◽  
Seismic Reflection Profiles

Abstract. The 2017 Mw 7.3 Iran–Iraq earthquake occurred in a region where the pattern of major plate convergence is well constrained, but limited information is available on the seismogenic structures. Geological observations, interpretation of seismic reflection profiles, and well data are used in this paper to build a regional, balanced cross section that provides a comprehensive picture of the geometry and dimensional parameters of active faults in the hypocentral area. Our results indicate (i) the coexistence of thin- and thick-skinned thrusting, (ii) the reactivation of inherited structures, and (iii) the occurrence of weak units promoting heterogeneous deformation within the palaeo-Cenozoic sedimentary cover and partial decoupling from the underlying basement. According to our study, the main shock of the November 2017 seismic sequence is located within the basement, along the low-angle Mountain Front Fault. Aftershocks unzipped the up-dip portion of the same fault. This merges with a detachment level located at the base of the Paleozoic succession, to form a crustal-scale fault-bend anticline. Size and geometry of the Mountain Front Fault are consistent with a down-dip rupture width of 30 km, which is required for an Mw 7.3 earthquake.

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