scholarly journals Deformation along an apparent seismic barrier: a palaeoseismological study along the North Anatolian Fault

1996 ◽  
Vol 39 (3) ◽  
Author(s):  
G. W. Michel ◽  
C. Janssen
Keyword(s):  
Strike Slip ◽  
North Anatolian Fault ◽  
Deformation Mechanisms ◽  
Normal Faulting ◽  
Short Term ◽  
The North ◽  
Spatial Changes ◽  
Major Fault ◽  
Event Triggered

An overstep in the North Anatolian Fault, possibly acting as a seismic barrier, was investigated for its structural and palaeoseismological characteristics. Study interests were: i) to find overstep related spatial changes in deformation which would help assess the structure as a long term singularity in the fault; ii) to identify short term, event-triggered changes in structures where the major fault enters the overstep i.e., in an area where seismogenic slip is impeded or even arrested; iii) to investigate whether or not the surface overstep is related to a seismic barrier, and iv) to discuss structures that might possibly be characteristic of barriers. In order to achieve this: a) largescale faults were mapped in the area, b) fault-slip data were measured in 56 outcrops along and within the overstep, and c) trenches were dug at the eastern rim of the overstep where recent earthquake structures had been reported. Derived long term stretching directions and ratios change significantly over the fault step and structures of recent major earthquakes suggest different deformation mechanisms for different events at the same Location e.g. strike-slip, thrust and normal faulting.

A Two-Scale Preparation Phase Preceded an Mw 5.8 Earthquake in the Sea of Marmara Offshore Istanbul, Turkey

2020 ◽  
Vol 91 (6) ◽  
pp. 3139-3147 ◽  
Author(s):  
Virginie Durand ◽  
Stephan Bentz ◽  
Grzegorz Kwiatek ◽  
Georg Dresen ◽  
Christopher Wollin ◽  
...  
Keyword(s):  
Matched Filter ◽  
Aseismic Slip ◽  
Sea Of Marmara ◽  
Spatiotemporal Evolution ◽  
Short Term ◽  
Filter Technique ◽  
The North ◽  
Preparation Phase ◽  
Scale Preparation

Abstract We analyze the spatiotemporal evolution of seismicity during a sequence of moderate (an Mw 4.7 foreshock and Mw 5.8 mainshock) earthquakes occurring in September 2019 at the transition between a creeping and a locked segment of the North Anatolian fault in the central Sea of Marmara, northwest Turkey. To investigate in detail the seismicity evolution, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two largest events are clearly seen, exhibiting two different behaviors: a long-term activation of the seismicity along the entire fault segment and a short-term concentration around the epicenters of the large events. We suggest a two-scale preparation phase, with aseismic slip preparing the mainshock final rupture a few days before, and a cascade mechanism leading to the nucleation of the mainshock. Thus, our study shows a combination of seismic and aseismic slip during the foreshock sequence changing the strength of the fault, bringing it closer to failure.

Coastal climatology of the North-Western Mediterranean area for long-term and short-term risk assessment.

2020 ◽  
Author(s):  
Carlo Brandini ◽  
Stefano Taddei ◽  
Valentina Vannucchi ◽  
Michele Bendoni ◽  
Bartolomeo Doronzo ◽  
...  
Keyword(s):  
Risk Assessment ◽  
High Resolution ◽  
Mediterranean Area ◽  
Western Mediterranean ◽  
Climate Trends ◽  
Short Term ◽  
The North ◽  
The Mediterranean ◽  
North Western

<p>In this work we present the results obtained through a dynamic downscaling of the ERA5 reanalysis dataset (hindcast) of ECMWF, using high-resolution meteorological and wave models defined on unstructured computation grids along the Mediterranean coasts, with a particular focus on the North-Western Mediterranean area. Downscaling of the ERA5 meteorological data is obtained through the BOLAM and MOLOCH models (up to a resolution of 2.5 km) which force an unstructured WW3 model with a resolution of up to 500 m along the coast. Models were validated through available meteorological stations, wave buoy data and X-band wave radars, the latter for the purposes of wave spectra validation.</p><p>On the one hand, this allowed, by extracting the time series of some attack parameters of the waves along the coast, and according to the type of coast (rocky coasts, sandy coasts, coastal structures etc.), to compute the return periods and to characterize the impact of any individual storm. On the other hand, it is possible to highlight some trends observed in the last 30 years, during which recent research is showing an increasing evidence  of some changes in global circulation at regional to local scales. These changes also include effects of wind rotation, wave regimes, storm surges, wave-induced coastal currents and coastal morphodynamics. For example, in the North-Western Mediterranean extreme events belonging to cyclonic weather-types circulation with stronger S-SE components (like the storm of October 28-30th 2018 and many others), rather than events associated with perturbations of Atlantic origin and zonal circulation, are becoming more frequent. These long-term wind/wave climate trends can have consequences not only in the assessment of long-term risk due to main morphodynamic variations (ie. coastal erosion), but also in the short-term risk assessment.</p><p>This work was funded by the EU MAREGOT project (2017-2020) and ECMWF Special Project spitbran  “Evaluation of coastal climate trends in the Mediterranean area by means of high-resolution and multi-model downscaling of ERA5 reanalysis” (2018-2020).</p>

Neotectonics of the SW Marmara region, NW Anatolia, Turkey

2006 ◽  
Vol 143 (2) ◽  
pp. 229-241 ◽  
Author(s):  
ÖMER FEYZI GÜRER ◽  
ERCAN SANGU ◽  
MUZAFFER ÖZBURAN
Keyword(s):  
Fault Zone ◽  
Structural Characteristics ◽  
Strike Slip ◽  
North Anatolian Fault ◽  
Marmara Region ◽  
Field Observations ◽  
Extensional Tectonics ◽  
North Anatolian Fault Zone ◽  
The North ◽  
Differential Movement

This study reports on the geometric and structural characteristics of the North Anatolian Fault Zone in the southwest Marmara region. The geometric and kinematic features of the faults in the region are described, based on field observations. In addition, the Neogene and Quaternary basin fill which occupies large areas in the region has been determined, and the tectonic regimes controlling these basins are explained. The neotectonic regime is also explained considering different deformation phases affecting the region. The N–S extension and E–W strike-slip have affected the region possibly since the latest Pliocene–Quaternary. Field observations show that these extensional tectonics around the south Marmara region are related to right strike-slip on the E–W North Anatolian fault zone and the N–S Aegean extensional system. The faults in this zone trend approximately E–W in the eastern part of the region and NE–SW towards the west of the region, indicating that they accommodate rotation in addition to differential movement between adjacent blocks.

scholarly journals Distributed earthquake focal mechanisms in the Aegean Sea

2018 ◽  
Vol 40 (3) ◽  
pp. 1125 ◽  
Author(s):  
A. Kiratzi ◽  
C. Benetatos ◽  
Z. Roumelioti
Keyword(s):  
Aegean Sea ◽  
Strike Slip ◽  
Focal Mechanisms ◽  
Normal Faulting ◽  
Small Magnitude ◽  
The North ◽  
Earthquake Focal Mechanisms ◽  
Reverse Faulting ◽  
Different Types ◽  
Transform Fault Zone

Nearly 2,000 earthquake focal mechanisms in the Aegean Sea and the surroundings for the period 1912- 2006, for 1.5 <M<7.5, and depths from 0 to 170 km, indicate a uniform distribution and smooth variation in orientation over wide regions, even for the very small magnitude earthquakes. ~ 60% of the focal mechanisms show normal faulting, that mainly strikes ~E-W. However, a zone ofN-S normal faulting runs the backbone of Albanides-Hellenides. Low-angle thrust and reverse faulting is confined in western Greece (Adria-Eurasia convergence) and along the Hellenic trench (Africa-Eurasia). In the central Aegean Sea the effect of the propagating tip of the North Anatolian Fault into the Aegean Sea is pronounced and strike-slip motions are widely distributed. Shearing does not cross central Greece. Strike-slip motions reappear in the Cephalonia-Lefkada Transform Fault zone and in western Péloponnèse, which shows very complex tectonics, with different types of faulting being oriented favourably and operating under the present stress-field. Moreover, in western Péloponnèse the sense of the observed shearing is not yet clear, whether it is dextral or sinistral, and this lack of data has significant implications for the orientation of the earthquake slip vectors compared to the GPS obtained velocity vectors.

scholarly journals VÝZKUM POZDNĚ KVARTÉRNÍ AKTIVITY ZLOMU KOSÍŘE V HORNOMORAVSKÉM ÚVALU ANEB PROČ JE DOBRÉ STUDOVAT SVAHOVINY A SEISMOGRAMY

2016 ◽  
Vol 22 (1-2) ◽  
Author(s):  
Petr Špaček ◽  
Vít Ambrož
Keyword(s):  
Late Pleistocene ◽  
Late Quaternary ◽  
Slip Rate ◽  
Fault Scarp ◽  
Strike Slip ◽  
Tectonic Activity ◽  
Temporary Increase ◽  
Normal Faulting ◽  
Major Fault ◽  
Complex Sequences

Preliminary results of a research into the late Quaternary slip of a major fault in the seismically active Upper Morava Basin are given. Three trenches, up to 6 m deep, were excavated at the foot of the Kosíř Fault scarp near Stařechovice and Čelechovice. The exposed complex sequences of colluvium and loess, now only partly dated by OSL and 14C, is heavily faulted. The faulting is explained by a tectonic slip at the Kosíř Fault and, in the Stařechovice trench, also by simultaneous slope deformations. None of the faults do off set the Holocene topsoil but the youngest of them were clearly active aft er the deposition of the youngest loess and indicate the slip of up to 1.4 m in Late Pleistocene. In Čelechovice trenches the minimum vertical throw of 4 m is indicated for the lower part of the sequence with assumed Late Pleistocene age. The geometry of the deformed zone suggests an oblique normal faulting with significant strike-slip component. The sense of shearing in the horizontal plane was not resolved. Minimum tectonic slip rate of 0.1‒0.3 mm/year in Late Pleistocene is suggested but this must be confi rmed by new dating. Our observations reveal surprisingly young and large deformation which may suggest a temporary increase of tectonic activity during Late Pleistocene.

scholarly journals Extreme Quaternary plate boundary exhumation and strike slip localized along the southern Fairweather fault, Alaska, USA

Geology ◽  
2021 ◽  
Vol 49 (5) ◽  
pp. 602-606 ◽  
Author(s):  
Richard O. Lease ◽  
Peter J. Haeussler ◽  
Robert C. Witter ◽  
Daniel F. Stockli ◽  
Adrian M. Bender ◽  
...  
Keyword(s):  
North America ◽  
Sedimentary Cover ◽  
Plate Boundary ◽  
Slip Rate ◽  
Strike Slip ◽  
Plate Motion ◽  
The North ◽  
Exhumation Rates ◽  
Restraining Bend

Abstract The Fairweather fault (southeastern Alaska, USA) is Earth’s fastest-slipping intracontinental strike-slip fault, but its long-term role in localizing Yakutat–(Pacific–)North America plate motion is poorly constrained. This plate boundary fault transitions northward from pure strike slip to transpression where it comes onshore and undergoes a &lt;25°, 30-km-long restraining double bend. To the east, apatite (U-Th)/He (AHe) ages indicate that North America exhumation rates increase stepwise from ∼0.7 to 1.7 km/m.y. across the bend. In contrast, to the west, AHe age-depth data indicate that extremely rapid 5–10 km/m.y. Yakutat exhumation rates are localized within the bend. Further northwest, Yakutat AHe and zircon (U-Th)/He (ZHe) ages gradually increase from 0.3 to 2.6 Ma over 150 km and depict an interval of extremely rapid &gt;6–8 km/m.y. exhumation rates that increases in age away from the bend. We interpret this migration of rapid, transient exhumation to reflect prolonged advection of the Cenozoic–Cretaceous sedimentary cover of the eastern Yakutat microplate through a stationary restraining bend along the edge of the North America plate. Yakutat cooling ages imply a long-term strike-slip rate (54 ± 6 km/m.y.) that mimics the millennial (53 ± 5 m/k.y.) and decadal (46 mm/yr) rates. Fairweather fault slip can account for all Pacific–North America relative plate motion throughout Quaternary time and indicates stability of highly localized plate boundary strike slip on a single fault where extreme rock uplift rates are persistently localized within a restraining bend.

Disintegration, Faulting and Seismogenesis of the North China Craton

1988 ◽  
Vol 59 (4) ◽  
pp. 247-250
Author(s):  
Ding Guoyu
Keyword(s):  
North China Craton ◽  
North China ◽  
Strike Slip ◽  
Normal Faulting ◽  
Strong Earthquakes ◽  
The Past ◽  
The North ◽  
Tectonic Framework ◽  
Yanshan Movement ◽  
High Seismicity

Abstract The North China Craton (NCC) began to disintegrate completely in the Yanshan Movement period (Jurassic-Cretaceous) forming a great number of NE, NEN, NW and WNW trending faults. Such fault systems have played an important role in the development of tectonics and seismicity in the Craton area. There has been a big change of stress field since the Pliocene, from predominantly normal faulting to predominantly strike-slip faulting. The NCC is an area with high seismicity. The recent seismicity is obviously controlled by the tectonic framework derived from Craton disintegration. Six strong earthquakes with M > 8.0 in this area have occurred in the past two thousand years. Many strong earthquakes in the NCC area are mainly caused by preexisting faults that move horizontally forming pull-apart basins.

Uplift history of the Western Ecuadorian Andes: new constraints from low-temperature thermochronology

2020 ◽  
Author(s):  
Audrey Margirier ◽  
Peter Reiners ◽  
Ismael Casado ◽  
Stuart Thomson ◽  
Alexandra Alvarado ◽  
...  
Keyword(s):  
Strike Slip ◽  
South American ◽  
South American Plate ◽  
Ridge Subduction ◽  
The North ◽  
Western Cordillera ◽  
Deformational History ◽  
History Of ◽  
Long Term Impact

&lt;p&gt;The Cenozoic growth of the Ecuadorian Andes has been strongly influenced by the compressional reactivation of inherited crustal anisotropies, strike-slip faulting and uplift, and the erosional effects of a wet tropical climate superposed on the deforming orogen. Some authors have linked uplift in the Western Cordillera to the interaction between the South American Plate and the subduction of the oceanic Carnegie Ridge. However, recent studies have alternatively suggested that the tectonic evolution of a northward-escaping crustal sliver in western Ecuador along the Pallatanga strike-slip zone may equally well explain mountain building and topographic growth in this region. While the importance of the Pallatanga Fault has been recognized in the context of seismic hazards, its long-term impact on the development of topography and relief has not been explored in detail. To evaluate the possible roles of oceanic ridge subduction and/or strike-slip motion in prompting the growth of the Western Cordillera, we present new thermochronological data to constrain the deformational history of the Western Cordillera at different latitudes. We focus on two sites in the vicinity of the Pallatanga strike-slip fault (3&amp;#176;S and 1&amp;#176;30&amp;#8217;S) and a location farther to the north (0&amp;#176;30&amp;#8217;N). Our apatite and zircon (U-Th-Sm)/He dates range from 26.0 &amp;#177; 0.4 Ma to 3.9 &amp;#177; 0.1 Ma and from 23.7 &amp;#177; 0.3 to 5.9 &amp;#177; 0.1 Ma, respectively. The three sampled sites record a clear age-elevation relationship. The inverse modeling of apatite and zircon (U-Th-Sm)/He dates and upcoming apatite fission-track data is expected to provide new constraints on the recent uplift and exhumation history of the Western Ecuadorian Andes and thus furnish information on the paleo-geographical evolution of the northern Andes.&lt;/p&gt;

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