Coastal ridge constructive processes at a multi-decadal scale in Barreta Island (southern Portugal)     

Xabier Herrero  Susana Costas  Katerina Kombiadou 《地球表面变化过程与地形》2020,45(2):411-423

Multiple ridges across prograding coasts may display variable geometries, commonly expressed through varying elevations. Changes in ridge elevation have been traditionally related to the occurrence of fluctuating progradation rates, which might, in turn, be driven by shifting environmental conditions. Here, we explore the geometry and growth mechanisms of multiple ridges, generated at Barreta Island (Ria Formosa, southern Portugal), as a consequence of the rapid progradation of the island over the last 70 years, following the artificial fixation of the downdrift Faro-Olhão inlet with jetties in 1955. The variability in the morphology of these features was analysed in combination with available wind and wave data, in order to better distinguish growth mechanisms and understand the main parameters determining the final geometry of the observed ridges. The results suggest that (1) most of the identified ridges fall in the beach ridge classification, as they have been mostly built by marine processes, and (2) the parameters derived from, or closely related to wave climate variability (e.g. progradation rates, storm occurrence) can jointly explain most of the observed morphological changes, while aeolian processes played a secondary role. Indeed, ridge geometry appears mainly controlled by progradation rates, with higher ridges associated with lower progradation rates. Progradation rate, in turn, is mostly related to longshore wave power, storminess, and the occurrence storm groups. Yet, the final configuration of ridges can also be affected by runup levels and onshore winds. Therefore, establishing the relation between ridge geometry and wave climate is not a straightforward task, because of the complex processes and interactions that control coastal morphodynamics. © 2019 John Wiley & Sons, Ltd.  相似文献   

Analysis of microseismicity associated with the 2017 seismic swarm near the Aegean coast of NW Turkey     

Maria Mesimeri  Christos Kourouklas  Eleftheria Papadimitriou  Vassilios Karakostas  Despoina Kementzetzidou 《Acta Geophysica》2018,66(4):479-495

A thorough spatiotemporal analysis of the intense seismic activity that took place near the Aegean coast of NW Turkey during January–March 2017 was conducted, aiming to identify its causative relation to the regional seismotectonic properties. In this respect, absolute and relative locations are paired and a catalog consisting of 2485 events was compiled. Relative locations are determined with high accuracy using the double-difference technique and differential times both from phase pick data and from cross-correlation measurements. The spatial distribution of the relocated events revealed a south-dipping causative fault along with secondary and smaller antithetic segments. Spatially, the seismicity started at the westernmost part and migrated with time to the easternmost part of the activated area. Temporally, two distinctive periods are observed, namely an early period lasting 1 month and a second period which includes the largest events in the sequence. The investigation of the interevent time distribution revealed a triggering mechanism, whereas the ETAS parameters show a strong external force (μ?>?1), which might be attributed to the existence of the Tuzla geothermal field.  相似文献   

Investigation of earthquake recurrence networks: the cases of 2014 and 2015 aftershock sequences in Ionian Islands,Greece     

Chorozoglou  D.  Papadimitriou  E. 《Natural Hazards》2020,102(3):783-805

Natural Hazards - The investigation of earthquake recurrence networks that were constructed from two aftershock sequences in Greece, is performed, aiming to detect whether the structure of networks...  相似文献   

Bounding surface plasticity model with reversal surfaces for the monotonic and cyclic shearing of sands     

Limnaiou  Taxiarchoula G.  Papadimitriou  Achilleas G. 《Acta Geotechnica》2023,18(1):235-263

Acta Geotechnica - The paper describes the formulation and simulative potential of a constitutive model for monotonic and cyclic shearing of sands. It is a SANISAND-type model that does not...  相似文献   

Statistical properties of aftershock rate decay: Implications for the assessment of continuing activity     

Aggeliki Adamaki  Eleftheria E. Papadimitriou  George M. Tsaklidis  Vassilios Karakostas 《Acta Geophysica》2011,59(4):748-769

Aftershock rates seem to follow a power law decay, but the assessment of the aftershock frequency immediately after an earthquake, as well as during the evolution of a seismic excitation remains a demand for the imminent seismic hazard. The purpose of this work is to study the temporal distribution of triggered earthquakes in short time scales following a strong event, and thus a multiple seismic sequence was chosen for this purpose. Statistical models are applied to the 1981 Corinth Gulf sequence, comprising three strong (M = 6.7, M = 6.5, and M = 6.3) events between 24 February and 4 March. The non-homogeneous Poisson process outperforms the simple Poisson process in order to model the aftershock sequence, whereas the Weibull process is more appropriate to capture the features of the short-term behavior, but not the most proper for describing the seismicity in long term. The aftershock data defines a smooth curve of the declining rate and a long-tail theoretical model is more appropriate to fit the data than a rapidly declining exponential function, as supported by the quantitative results derived from the survival function. An autoregressive model is also applied to the seismic sequence, shedding more light on the stationarity of the time series.  相似文献   

Symmetric scaling properties in global surface air temperature anomalies     

Costas A. Varotsos  Maria N. Efstathiou 《Theoretical and Applied Climatology》2015,121(3-4):767-773

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Sedimentary Deposits from the 17 July 2006 Western Java Tsunami,Indonesia: Use of Grain Size Analyses to Assess Tsunami Flow Depth,Speed, and Traction Carpet Characteristics     

Andrew Moore  James Goff  Brian G. McAdoo  Hermann M. Fritz  Aditya Gusman  Nikos Kalligeris  Kenia Kalsum  Arif Susanto  Debora Suteja  Costas E. Synolakis 《Pure and Applied Geophysics》2011,168(11):1951-1961

The 2006 western Java tsunami deposited a discontinuous sheet of sand up to 20 cm thick, flooded coastal southern Java to a depth of at least 8 m and inundated up to 1 km inland. In most places the primarily heavy mineral sand sheet is normally graded, and in some it contains complex internal stratigraphy. Structures within the sand sheet probably record the passage of up to two individual waves, a point noted in eyewitness accounts. We studied the 2006 tsunami deposits in detail along a flow parallel transect about 750 m long, 15 km east of Cilacap. The tsunami deposit first becomes discernable from the underlying sediment 70 m from the shoreline. From 75 to 300 m inland the deposit has been laid down in rice paddies, and maintains a thickness of 10–20 cm. Landward of 300 m the deposit thins dramatically, reaching 1 mm by 450 m inland. From 450 m to the edge of deposition (around 700 m inland) the deposit remains <1 mm thick. Deposition generally attended inundation—along the transect, the tsunami deposited sand to within about 40 m of the inundation limit. The thicker part of the deposit contains primarily sand indistinguishable from that found on the beach 3 weeks after the event, but after about 450 m (and roughly coinciding with the decrease in thickness) the tsunami sediment shifts to become more like the underlying paddy soil than the beach sand. Grain sizes within the deposit tend to fine upward and landward, although overall upward fining takes place in two discrete pulses, with an initial section of inverse grading followed by a section of normal grading. The two inversely graded sections are also density graded, with denser grains at the base, and less dense grains at the top. The two normally graded sections show no trends in density. The inversely graded sections show high density sediment to the base and become less dense upward and represents traction carpet flows at the base of the tsunami. These are suggestive of high shear rates in the flow. Because of the grain sorting in the traction carpet, the landward-fining trends usually seen in tsunami deposits are masked, although lateral changes of mean sediment grain size along the transect do show overall landward fining, with more variation as the deposit tapers off. The deposit is also thicker in the more seaward portions than would be produced by tsunamis lacking traction carpets.  相似文献   

The global signature of the ENSO and SST-like fields   总被引：1，自引：1，他引：0  

Costas A. Varotsos 《Theoretical and Applied Climatology》2013,113(1-2):197-204

The El Niño–Southern Oscillation (ENSO)-like variability of various parameters and indices (e.g. sea surface temperature (SST)) is explored, by employing the last six decades of data on a global scale. We found that the ENSO signal in the SST field extends over tropics and subtropics, becoming maximum around 30° N and 30° S. The pronounced ENSO signal in the SST is observed over the southern tropics and subtropics. Additionally, the investigation of regional links between the Pacific Decadal Oscillation and SST revealed a new regional link, which extends in the tropical southern Pacific Ocean, where the effects of a long-lived pattern of SST are taking place. Furthermore, very strong SST-like surface temperature behaviour is observed over the equatorial Indian Ocean, being a new input to the assessment of “dangerous anthropogenic interference”. The above-mentioned findings could be employed to the advanced modelling development to improve climate change projections.  相似文献   

Explicit integration of bounding surface model for the analysis of earthquake soil liquefaction     

Konstantinos I. Andrianopoulos  Achilleas G. Papadimitriou  George D. Bouckovalas 《国际地质力学数值与分析法杂志》2010,34(15):1586-1614

This paper presents a new plasticity model developed for the simulation of monotonic and cyclic loading of non‐cohesive soils and its implementation to the commercial finite‐difference code FLAC, using its User‐Defined‐Model (UDM) capability. The new model incorporates the framework of Critical State Soil Mechanics, while it relies upon bounding surface plasticity with a vanished elastic region to simulate the non‐linear soil response. Stress integration of constitutive relations is performed using a recently proposed explicit scheme with automatic error control and substepping, which so far has been employed in the literature only for constitutive models aiming at monotonic loading. The overall accuracy of this scheme is evaluated at element level by simulating cyclic loading along complex stress paths and by using iso‐error maps for paths involving change of the Lode angle. The performance of the new constitutive model and its stress integration scheme in complex boundary value problems involving earthquake‐induced liquefaction is evaluated, in terms of accuracy and computational cost, via a number of parametric analyses inspired by the successful simulation of the VELACS centrifuge Model Test No. 2 studying the lateral spreading response of a liquefied sand layer. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Sociological aspects of natural hazards     

N. Nirupama  Costas Armenakis 《Natural Hazards》2013,66(1):1-2

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