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

2007 ◽  
Vol 1 (3) ◽  
pp. 139-153 ◽  
Author(s):  
IAIN S. Stewart ◽  
PAUL L. Hancock
Keyword(s):  
Fault Zone ◽  
Normal Fault ◽  
Fault Scarp ◽  
Aegean Region

Mixed-mode Slip Behavior and Strength Evolution of an Actively Exhuming Low-Angle Normal Fault, Woodlark Rift, SE Papua New Guinea

2020 ◽  
Author(s):  
Marcel Mizera ◽  
Timothy Little ◽  
Carolyn Boulton ◽  
James Biemiller ◽  
David Prior
Keyword(s):  
Papua New Guinea ◽  
Fault Zone ◽  
Normal Fault ◽  
New Guinea ◽  
Grain Boundary Sliding ◽  
Fault Scarp ◽  
Geochemical Data ◽  
Fault Rock ◽  
Fault Rocks ◽  
Crystallographic Preferred Orientation

<p>Rapid dip-slip (11.7±3.5 mm/yr) on the active Mai'iu low-angle normal fault in SE Papua New Guinea enabled the preservation of early formed microstructures in mid to shallow crustal rocks. The corrugated, convex-upward shaped fault scarp dips as low as 16°–20° near its trace close to sea level and forms a continuous landscape surface traceable for at least 28 km in the NNE slip-direction. Structurally, offset on the Mai'iu fault has formed a metamorphic core complex and has exhumed a metabasaltic footwall during 30–45 km of dip slip on a rolling-hinge style detachment fault. The exhumed crustal section records the spatiotemporal evolution of fault rock deformation mechanisms and the differential stresses that drive slip on this active low-angle normal fault.</p><p>The Mai'iu fault exposes a <3 m-thick fault core consisting of gouges and cataclasites. These deformed units overprint a structurally underlying carapace of metabasaltic mylonites that are locally >60 m-thick. Detailed microstructural, textural and geochemical data combined with chlorite-based geothermometry of these fault rocks reveal a variety of deformation processes operating within the Mai'iu fault zone. A strong crystallographic preferred orientation of non-plastically deformed actinolite in a pre-existing, fine-grained (6–33 µm) mafic assemblage indicates that mylonitic deformation was controlled by diffusion-accommodated grain-boundary sliding together with syn-tectonic chlorite precipitation at >270–370°C. At shallower crustal levels on the fault (T≈150–270°C), fluid-assisted mass transfer and metasomatic reactions created a foliated cataclasite fabric during inferred periods of aseismic creep. Pseudotachylites and ultracataclasites mutually cross-cut both the foliations and one another, recording repeated episodes of seismic slip. In these fault rocks, paleopiezometry based on calcite twinning yields peak differential stresses of ~140–185 MPa at inferred depths of 8–12 km. These differential stresses were high enough to drive continued slip on a ~35° dipping segment of the Mai'iu fault, and to cause new brittle yielding of strong mafic rocks in the exhuming footwall of that fault. In the uppermost crust (<8 km; T<150°C), where the Mai'iu fault dips shallowly and is most severely misoriented for slip, actively deforming fault rocks are clay-rich gouges containing abundant saponite, a frictionally weak mineral (µ<0.28).</p><p>In summary, these results combined with fault dislocation models of GPS velocities from campaign stations in this region suggest a combination of brittle frictional and viscous flow processes within the Mai'iu fault zone. Gouges of the Mai'iu fault have been strongly altered by fluids and are frictionally weak near the surface, where the fault is most strongly misoriented. At greater depths (8–12 km) the fault is stronger and slips both by aseismic creep and episodic earthquakes (a mixture of fast and slow slip) in response to locally high differential stresses.</p>

scholarly journals Morphotectonic Analysis along the Northern Margin of Samos Island, Related to the Seismic Activity of October 2020, Aegean Sea, Greece

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 102
Author(s):  
Paraskevi Nomikou ◽  
Dimitris Evangelidis ◽  
Dimitrios Papanikolaou ◽  
Danai Lampridou ◽  
Dimitris Litsas ◽  
...  
Keyword(s):  
Fault Zone ◽  
Seismic Activity ◽  
Volcanic Rocks ◽  
Active Tectonics ◽  
Normal Fault ◽  
Aegean Sea ◽  
Northern Margin ◽  
The North ◽  
Eastern Aegean ◽  
Half Graben

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.

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

Geosciences ◽  
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.

scholarly journals Neogene-Quaternary tectonic regime and macroseismic observations in the Tyrnavos-Elassona broader epicentral area of the March 2021, intense earthquake sequence

2021 ◽  
Vol 58 ◽  
pp. 200
Author(s):  
Dimitrios Galanakis ◽  
Sotiris Sboras ◽  
Garyfalia Konstantopoulou ◽  
Markos Xenakis
Keyword(s):  
Normal Fault ◽  
Fault Scarp ◽  
Focal Mechanisms ◽  
Fault System ◽  
Spatiotemporal Evolution ◽  
Surface Rupture ◽  
Alluvial Deposits ◽  
Epicentral Area ◽  
Ground Shaking ◽  
Macroseismic Observations

On March 3, 2021, a strong (Mw6.3) earthquake occurred near the towns of Tyrnavos and Elassona. One day later (March 4), a second strong (Mw6.0) earthquake occurred just a few kilometres toward the WNW. The aftershock spatial distribution and the focal mechanisms revealed NW-SE-striking normal faulting. The focal mechanisms also revealed a NE-SW oriented extensional stress field, different from the orientation we knew so far (ca. N-S). The magnitude and location of the two strongest shocks, and the spatiotemporal evolution of the sequence, strongly suggest that two adjacent fault segments were ruptured respectively. The sequence was followed by several coseismic ground deformational phenomena, such as landslides/rockfalls, liquefaction and ruptures. The landslides and rockfalls were mostly associated with the ground shaking. The ruptures were observed west of the Titarissios River, near to the Quaternary faults found by bore-hole lignite investigation. In the same direction, a fault scarp separating the alpidic basement from the alluvial deposits of the Titarissios valley implies the occurrence of a well-developed fault system. Some of the ground ruptures were accompanied by extensive liquefaction phenomena. Others cross-cut reinforced concrete irrigation channels without changing their direction. We suggest that this fault system was partially reactivated, as a secondary surface rupture, during the sequence as a steeper splay of a deeper low-to-moderate angle normal fault.

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

2005 ◽  
Vol 401 (3-4) ◽  
pp. 143-166 ◽  
Author(s):  
Helmuth Sölva ◽  
Bernhard Grasemann ◽  
Martin Thöni ◽  
Rasmus Thiede ◽  
Gerlinde Habler
Keyword(s):  
Fault Zone ◽  
Normal Fault ◽  
Eastern Alps ◽  
Normal Faulting

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

2013 ◽  
Vol 608 ◽  
pp. 468-481 ◽  
Author(s):  
Mike Haertel ◽  
Marco Herwegh ◽  
Thomas Pettke
Keyword(s):  
Fault Zone ◽  
Normal Fault ◽  
Quartz Veins

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

2013 ◽  
Vol 57 ◽  
pp. 58-80 ◽  
Author(s):  
S. Noorsalehi-Garakani ◽  
G.J. Kleine Vennekate ◽  
P. Vrolijk ◽  
J.L. Urai
Keyword(s):  
Fault Zone ◽  
Normal Fault ◽  
First Results

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

1966 ◽  
Vol 3 (5) ◽  
pp. 639-658 ◽  
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.

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

Geosciences ◽  
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.

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

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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