Clay-smear continuity and normal fault zone geometry – First results from excavated sandbox models

On 30 October 2020, a strong earthquake of magnitude 7.0 occurred north of Samos Island at the Eastern Aegean Sea, whose earthquake mechanism corresponds to an E-W normal fault dipping to the north. During the aftershock period in December 2020, a hydrographic survey off the northern coastal margin of Samos Island was conducted onboard R/V NAFTILOS. The result was a detailed bathymetric map with 15 m grid interval and 50 m isobaths and a morphological slope map. The morphotectonic analysis showed the E-W fault zone running along the coastal zone with 30–50° of slope, forming a half-graben structure. Numerous landslides and canyons trending N-S, transversal to the main direction of the Samos coastline, are observed between 600 and 100 m water depth. The ENE-WSW oriented western Samos coastline forms the SE margin of the neighboring deeper Ikaria Basin. A hummocky relief was detected at the eastern margin of Samos Basin probably representing volcanic rocks. The active tectonics characterized by N-S extension is very different from the Neogene tectonics of Samos Island characterized by NE-SW compression. The mainshock and most of the aftershocks of the October 2020 seismic activity occur on the prolongation of the north dipping E-W fault zone at about 12 km depth.

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Seismic Activity of the Manisa Fault Zone in Western Turkey Constrained by Cosmogenic 36Cl Dating

Geosciences ◽

10.3390/geosciences11110451 ◽

2021 ◽

Vol 11 (11) ◽

pp. 451

Author(s):

Nasim Mozafari ◽

Çağlar Özkaymak ◽

Dmitry Tikhomirov ◽

Susan Ivy-Ochs ◽

Vasily Alfimov ◽

...

Keyword(s):

Fault Zone ◽

Normal Fault ◽

Vertical Displacement ◽

Historical Records ◽

Western Turkey ◽

Slip Rates ◽

Vertical Displacements ◽

Surface Ruptures ◽

Fault Scarps ◽

Calculated Average

This study reports on the cosmogenic 36Cl dating of two normal fault scarps in western Turkey, that of the Manastır and Mugırtepe faults, beyond existing historical records. These faults are elements of the western Manisa Fault Zone (MFZ) in the seismically active Gediz Graben. Our modeling revealed that the Manastır fault underwent at least two surface ruptures at 3.5 ± 0.9 ka and 2.0 ± 0.5 ka, with vertical displacements of 3.3 ± 0.5 m and 3.6 ± 0.5 m, respectively. An event at 6.5 ± 1.6 ka with a vertical displacement of 2.7 ± 0.4 m was reconstructed on the Mugırtepe fault. We attribute these earthquakes to the recurring MFZ ruptures, when also the investigated faults slipped. We calculated average slip rates of 1.9 and 0.3 mm yr−1 for the Manastır and Mugırtepe faults, respectively.

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The Schneeberg Normal Fault Zone: Normal faulting associated with Cretaceous SE-directed extrusion in the Eastern Alps (Italy/Austria)

Tectonophysics ◽

10.1016/j.tecto.2005.02.005 ◽

2005 ◽

Vol 401 (3-4) ◽

pp. 143-166 ◽

Cited By ~ 42

Author(s):

Helmuth Sölva ◽

Bernhard Grasemann ◽

Martin Thöni ◽

Rasmus Thiede ◽

Gerlinde Habler

Keyword(s):

Fault Zone ◽

Normal Fault ◽

Eastern Alps ◽

Normal Faulting

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Titanium-in-quartz thermometry on synkinematic quartz veins in a retrograde crustal-scale normal fault zone

Tectonophysics ◽

10.1016/j.tecto.2013.08.042 ◽

2013 ◽

Vol 608 ◽

pp. 468-481 ◽

Cited By ~ 18

Author(s):

Mike Haertel ◽

Marco Herwegh ◽

Thomas Pettke

Keyword(s):

Fault Zone ◽

Normal Fault ◽

Quartz Veins

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Normal fault zone evolution and fault scarp degradation in the Aegean region

Basin Research ◽

10.1111/j.1365-2117.1988.tb00011.x ◽

2007 ◽

Vol 1 (3) ◽

pp. 139-153 ◽

Cited By ~ 41

Author(s):

IAIN S. Stewart ◽

PAUL L. Hancock

Keyword(s):

Fault Zone ◽

Normal Fault ◽

Fault Scarp ◽

Aegean Region

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THE ST. LAWRENCE VALLEY SYSTEM: A NORTH AMERICAN EQUIVALENT OF THE EAST AFRICAN RIFT VALLEY SYSTEM

Canadian Journal of Earth Sciences ◽

10.1139/e66-045 ◽

1966 ◽

Vol 3 (5) ◽

pp. 639-658 ◽

Cited By ~ 127

Author(s):

P. S. Kumarapeli ◽

V. A. Saull

Keyword(s):

Fault Zone ◽

Rift Valley ◽

Continental Drift ◽

Normal Fault ◽

Tectonic Activity ◽

Rift System ◽

East African ◽

Igneous Activity ◽

Distinctive Type ◽

African Rift

The St. Lawrence valley system (including the St. Lawrence, Ottawa, and Champlain valleys, and the St. Lawrence or Cabot trough) is coextensive with a well-defined pattern of seismic activity. The valley system is in a region of general updoming, normal faulting, and alkaline igneous activity of a distinctive type. The main phase of tectonic activity probably dates back to Mesozoic time. The above and other evidence presented in this paper indicate the existence of a major rift valley system that may be called the St. Lawrence rift system.The Rough Creek – Kentucky River fault zone, and the normal fault zones in Texas and Oklahoma, and the Lake Superior fault zone probably represent extensions of the St. Lawrence rift system. However, current seismicity indicates that the present tectonic activity is along a straight zone running through lakes Ontario and Erie into the Mississippi embayment. The St. Lawrence rift system may also be connected with the mid-Atlantic rift, in the region of the Azores plateau.The rift hypothesis presented may be useful as a regional guide in the search for niobium-bearing alkaline complexes and diamond-bearing kimberlites.Crustal tension in the St. Lawrence region may be genetically related to the opening of the Atlantic basin as postulated in the hypothesis of continental drift.

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Μorphometric Analysis for the Assessment of Relative Tectonic Activity in Evia Island, Greece

Geosciences ◽

10.3390/geosciences10070264 ◽

2020 ◽

Vol 10 (7) ◽

pp. 264

Author(s):

Kanella Valkanou ◽

Efthimios Karymbalis ◽

Dimitris Papanastassiou ◽

Mauro Soldati ◽

Christos Chalkias ◽

...

Keyword(s):

Spatial Distribution ◽

Fault Zone ◽

Normal Fault ◽

Morphometric Parameters ◽

Tectonic Activity ◽

Asymmetry Factor ◽

Drainage Basins ◽

Fault Systems ◽

The North ◽

Integrated Index

The aim of this study is to evaluate the relative tectonic activity in the north part of the Evia Island, located in Central Greece, and to investigate the contribution of neotectonic processes in the development of the fluvial landscape. Five morphometric parameters, including Drainage Basin Slope (Sb), Hypsometric Integral (Hi), Asymmetry Factor (Af), Relief Ratio (Rh), and Melton’s Ruggedness Number (M), were estimated for a total of 189 drainage basins. The catchments were classified into two groups, according to the estimated values of each morphometric parameter, and maps showing their spatial distribution were produced. The combination of the calculated morphometric parameters led to a new single integrated Index of relative tectonic activity (named Irta). Following this indexing, the basins were characterized as of low, moderate, or high relative tectonic activity. The quantitative analysis showed that the development of the present drainage systems and the geometry of the basins of the study area have been influenced by the tectonic uplift caused by the activity of two NW-SE trending offshore active normal fault systems: the north Gulf of Evia fault zone (Kandili-Telethrion) and the Aegean Sea fault zone (Dirfis), respectively. The spatial distribution of the values of the new integrated index Irta showed significant differences among the drainage basins that reflect differences in relative tectonic activity related to their location with regard to the normal fault systems of the study area.

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Numerical modelling technique for predicting the seismic fault zone (SFZ) in the earthquakes affected area, NW Himalayas with its neotectonic implication

Journal of Life and Earth Science ◽

10.3329/jles.v2i2.7499 ◽

1970 ◽

Vol 2 (2) ◽

pp. 57-65

Author(s):

M Farhad Howladar ◽

Sharmin Afroz ◽

Shofiqul Islam

Keyword(s):

Fault Zone ◽

Numerical Technique ◽

Strain Analysis ◽

Normal Fault ◽

Focal Mechanism Solution ◽

Mathematical Form ◽

Finite Elements Analysis ◽

Nw Himalaya ◽

Potential Region ◽

Seismic Fault

Finite elements analysis is a powerful tool, often used for analyzing problems on stress, that can be successfully employed to analyze the finite deformation of geological structures in a mathematical form on a digital computer. Over the last century, great earthquakes with magnitudes of 7->8 have struck in the NW Himalaya; the 1905 Kangra earthquake is one of them. This study performed a plane strain analysis of failure stress and faults in these earthquakes potential region based on the seismic geologic cross profile employing the two-dimensional finite element method under elastic material state with Mohr Coulomb failure criterion. The results show that the normal fault initiates at deeper level, whereas with increasing convergent displacement the thrust fault appears in the shallower region. The results of the simulation are compared with the available seismic and earthquakes focal mechanism solution data of the area which shows the close similarities between the distribution of simulated fault and microseismicity in the deeper region of Chamba Nappe (CN) and along the upper part of the Mid Crustal Ramp (MCR) which might be the Seismic Fault Zone (SFZ) of the region. Moreover, the intense localization of faults along the frontal part of the model indicates that this part is active in nature at present, which is responsible for the neotectonics in the Himalayas. Keywords: NW Himalaya; numerical technique; seismic fault zone; neotectonics DOI: 10.3329/jles.v2i2.7499 J. Life Earth Sci., Vol. 2(2) 57-65, 2007

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Outcrops and well logs as a practicum for calibrating the accuracy of traveltime tomograms

Interpretation ◽

10.1190/int-2014-0217.1 ◽

2015 ◽

Vol 3 (3) ◽

pp. SY27-SY40 ◽

Cited By ~ 5

Author(s):

Sherif M. Hanafy ◽

Ann Mattson ◽

Ronald L. Bruhn ◽

Shengdong Liu ◽

Gerard T. Schuster

Keyword(s):

High Resolution ◽

Fault Zone ◽

Great Basin ◽

Seismic Tomography ◽

Seismic Data ◽

Hanging Wall ◽

Normal Fault ◽

Well Logs ◽

Drill Core ◽

Sufficient Detail

We have developed two case studies demonstrating the use of high-resolution seismic tomography and reflection imaging in the field of paleoseismology. The first study, of the Washington fault in southern Utah, USA, evaluated the subsurface deposits in the hanging wall of the normal fault. The second study, of the Mercur fault in the eastern Great Basin of Utah, USA, helped to establish borehole locations for sampling subsurface colluvial deposits buried deeper than those previously trenched along the fault zone. We evaluated the seismic data interpretations by comparison with data obtained by trenching and logging deposits across the Washington fault, and by drill-core sampling and video logging of boreholes penetrating imaged deposits along the Mercur fault. The seismic tomograms provided critical information on colluvial wedges and faults but lacked sufficient detail to resolve individual paleoearthquakes.

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