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1.
Strong earthquake occurrence (M ≥ 6.0) onshore and offshore the Cyprus Island constitutes significant seismic hazard because they occur close to populated areas. Seismicity is weak south of the Island along the Cyprean Arc and strong events are aligned along the Paphos transform fault and Larnaka thrust fault zone that were already known and the Lemessos thrust fault zone that defined in the present study. By combining the past history of strong (M ≥ 6.0) events and the long-term tectonic loading on these major fault zones, the evolution of the stress field from 1896 until the present is derived. Although uncertainties exist in the location, magnitude and fault geometries of the early earthquakes included in our stress evolutionary model, the resulting stress field provides an explanation of later earthquake triggering. It was evidenced that the locations of all the strong events were preceded by a static stress change that encouraged failure. The current state of the evolved stress field may provide evidence for the future seismic hazard. Areas of positive static stress changes were identified in the southwestern offshore area that can be considered as possible sites of future seismic activity. 相似文献
2.
We investigate the sensitivity of the transient climate change to a tidal mixing scheme. The scheme parameterizes diapycnal diffusivity depending on the location of energy dissipation over rough topography, whereas the standard configuration uses horizontally constant diffusivity. We perform ensemble climate change experiments with two setups of MPIOM/ECHAM5, one setup with the tidal mixing scheme and the second setup with the standard configuration. Analysis of the responses of the transient climate change to CO2 increase reveals that the implementation of tidal mixing leads to a significant reduction of the transient surface warming by 9 %. The weaker surface warming in the tidal run is localized particularly over the Weddell Sea, likely caused by a stronger ocean heat uptake in the Southern Ocean. The analysis of the ocean heat budget reveals that the ocean heat uptake in both experiments is caused by changes in convection and advection. In the upper ocean, heat uptake is caused by reduced convection and enhancement of the Deacon Cell, which appears also in isopycnal coordinates. In the deeper ocean, heat uptake is caused by reduction of convective cooling associated with the circulation polewards of 65°S. Tidal mixing leads to stronger heat uptake in the Southern Ocean by causing stronger changes in advection, namely a stronger increase in the Deacon Cell and a stronger reduction in advective cooling by the circulation polewards of 65°S. Counter-intuitively, the relation between tidal mixing and greater heat storage in the deep ocean is an indirect one, through the influence of tidal mixing on the circulation. 相似文献
3.
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
4.
The occurrence of three endocrine disrupting compounds, 4-n-nonylphenol, triclosan and bisphenol A, was investigated in different bivalves originating from the Aegean Sea (Greece). The bioconcentration potential of these compounds was studied using the Mediterranean mussel (Mytilus galloprovincialis). Tissue samples were extracted by sonication. Analysis was performed by gas chromatography-mass spectrometry. According to the field survey results, the average concentrations of 4-n-nonylphenol, triclosan and bisphenol A, were 158, 461 and 404 ng g−1 (dry weight), respectively. During 28 days of exposure at 300 ng L−1, the tissue concentrations of compounds were constantly increased. Steady state was not observed up to the end of the experiment. Kinetic bioconcentration factors varied from 1.7 (4-n-nonylphenol and triclosan) to 4.5 L g−1 (bisphenol A). Following exposure, mussels were relocated to clean water for 28 days. This experiment revealed that depuration rates for all of the target compounds were lower than uptake rates. The biological half-lives of each compound ranged between 12 days (triclosan) and 26 days (bisphenol A). 相似文献
5.
The M
w
6.2 Lefkada earthquake occurred on 14 August 2003 beneath the western coastline of Lefkada Island. The main shock was followed
by an intense aftershock activity, which formed a narrow band extending over the western coast of the Island and the submarine
area between Lefkada and Kefalonia Islands, whereas additional off fault aftershocks formed spatial clusters on the central
and northwestern part of the Island. The aftershock spatial distribution revealed the activation of along-strike adjacent
fault segment as well as of secondary faults close to the main rupture. The properties of the activated segments were illuminated
by the precisely located aftershocks, fault plane solutions determination and the cross sections performed parallel and normal
to their strike. The aftershock focal mechanisms exhibited mainly strike slip faulting throughout the activated area, although
deviation of the dominant stress pattern is also observed. The results help to emphasize the importance of the identification
of activated nearby fault segments possibly triggered by the main rupture. Because such segments are capable to produce moderate
events causing appreciable damage, they should be viewed with caution in seismic hazard assessment in addition to the major
regional faults. 相似文献
6.
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
7.
Eleftheria?PapadimitriouEmail author Xueze?Wen Vassilios?Karakostas Xueshen?Jin 《Pure and Applied Geophysics》2004,161(8):1683-1707
Western Sichuan is among the most seismically active regions in southwestern China and is characterized by frequent strong (M 6.5) earthquakes, mainly along the Xianshuihe fault zone. Historical and instrumental seismicity show a temporal pattern of active periods separated by inactive ones, while in space a remarkable epicenter migration has been observed. During the last active period starting in 1893, the sinistral strike–slip Xianshuihe fault of 350 km total length, was entirely broken with the epicenters of successive strong earthquakes migrating along its strike. This pattern is investigated by resolving changes of Coulomb failure function (CFF) since 1893 and hence the evolution of the stress field in the area during the last 110 years. Coulomb stress changes were calculated assuming that earthquakes can be modeled as static dislocations in an elastic halfspace, and taking into account both the coseismic slip in strong (M 6.5) earthquakes and the slow tectonic stress buildup associated with major fault segments. The stress change calculations were performed for faults of strike, dip, and rake appropriate to the strong events. We evaluate whether these stress changes brought a given strong earthquake closer to, or sent it farther from, failure. It was found that all strong earthquakes, and moreover, the majority of smaller events for which reliable fault plane solutions are available, have occurred on stress–enhanced fault segments providing a convincing case in which Coulomb stress modeling gives insight into the temporal and spatial manifestation of seismic activity. We extend the stress calculations to the year 2025 and provide an assessment for future seismic hazard by identifying the fault segments that are possible sites of future strong earthquakes. 相似文献
8.
Eleftheria E. Papadimitriou 《Natural Hazards》1994,9(3):303-321
Earthquake recurrence intervals for large and great shallow mainshocks in 12 seismogenic sources along the North Pacific seismic zone (Alaska-Aleutians-Kamchatka-Kuril Islands) have been estimated and used for the determination of the following relations:
相似文献
9.
The long-term probabilistic seismic hazard of central Ionian Islands (Greece) is studied through the application of stress
release models. In order to identify statistically distinct regions, the study area is divided into two subareas, namely Kefalonia
and Lefkada, on the basis of seismotectonic properties. Previous results evidenced the existence of stress transfer and interaction
between the Kefalonia and Lefkada fault segments. For the consideration of stress transfer and interaction, the linked stress
release model is applied. A new model is proposed, where the hazard rate function in terms of X(t) has the form of the Weibull distribution. The fitted models are evaluated through residual analysis and the best of them
is selected through the Akaike information criterion. Based on AIC, the results demonstrate that the simple stress release
model fits the Ionian data better than the non-homogeneous Poisson and the Weibull models. Finally, the thinning simulation
method is applied in order to produce simulated data and proceed to forecasting. 相似文献
10.
Eleftheria?PapadimitriouEmail author Georgios?Sourlas Vassilios?Karakostas 《Pure and Applied Geophysics》2005,162(5):783-804
The largest earthquake (M0=4.9·1027 dyn·cm) of the 20th century in the territory of Greece occurred south of Amorgos Island, causing extensive destruction in the southern Aegean area. It occurred on an ENE–trending normal fault that is seated parallel to the Islands southern coastline. Changes in the rates of moderate–size earthquakes (M 5.0) that occurred before and after the Amorgos earthquake, within circular regions centered on its epicenter with radii of 100, 150 and 200 km, are investigated. The rate for moderate–size events just before the main shock appears to be considerably increased when compared to those of either preceding or subsequent periods. Further inspection reveals that more evident seismicity fluctuations are attributed to distances exceeding 100 km. These changes may be indicative of a broad region that is approaching a high stress state prior to an eventual large earthquake. Close to the main event, that is, within the 100–km radius, a remarkable quiescence period lasting about two decades before its occurrence was observed. Changes in seismicity are discussed in combination with static stress changes calculated by the application of the stress evolutionary model that takes into account the coseismic slip associated with the larger events (M 6.5) since the beginning of the 20th century and the tectonic loading on the major faults in the study area. These larger events, as with the intermediate magnitude seismicity taking place at distances exceeding 100 km and which encircled the quiescent area observed during the last 22 years before the Amorgos earthquake, are well correlated with stress-enhanced areas in each stage of the evolutionary model. 相似文献
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