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51.
E.M. Scordilis C.B. Papazachos G.F. Karakaisis V.G. Karakostas 《Journal of Seismology》2004,8(1):57-70
Time accelerating Benioff strain releasebefore the mainshock has been observed inall five cases of strong (M > 6.0) shallowmainshocks, which have occurred during thelast four decades in the area surroundingthe Adriatic Sea. This observation supportsthe idea that strong mainshocks arepreceded by accelerating seismic crustaldeformation due to the generation ofintermediate magnitude shocks (preshocks).It is further shown that the values ofparameters calculated from these datafollow appropriately modified relations,which have previously been proposed asadditional constraints to the criticalearthquake model and to the correspondingmethod of intermediate term earthquakeprediction. Thus, these results show thatthe identification of regions wheretime-accelerating Benioff strain followssuch constraints may lead to usefulinformation concerning the epicenter,magnitude and origin time of oncomingstrong mainshocks in this area. Theprocedure for identification of thetime-acceleration is validated byappropriate application on synthetic butrealistic random catalogues. Largerdimension of critical regions in Adriaticcompared to such regions in the Aegean isattributed to an order of magnitude smallerseismic deformation of the crust in theformer in comparison to the latter. 相似文献
52.
53.
Eleni E. Kalogirou Theodoros M. Tsapanos Vassilios G. Karakostas Vassilios P. Marinos Alexandros Chatzipetros 《Acta Geophysica》2014,62(6):1387-1412
In the beginning of July 2010, a ground fissure was observed in the field near the village of Mavropigi (Northern Greece) and specifically in its NW side. Later on (early September), a second ground fissure was perceived, close and almost parallel to the first one and very close to the limits of the lignite exploitation mine (by the Public Power Corporation, PPC). It was observed that the village of Mavropigi slides away slowly towards the PPC lignite mine. Geological, seismological, as well as geotechnical survey in the field indicated that the phenomenon is related to the coal mining exploitation in the near vicinity of the village rather than to any seismotectonic activity in the surrounding area. 相似文献
54.
An M8.3 earthquake struck the southwestern part of the Hellenic Arc, near the Island of Crete, in AD 365, generating a tsunami
that affected almost the entire eastern Mediterranean region. Taking into account that the time history of seismicity in this
region is fairly complete for such earthquakes in the historical catalog, which can be dated as back as the 5th century B.C.,
there is no indication that this segment of plate boundary has been fully ruptured again. The seismic hazard associated with
this part of the Hellenic Arc necessitates the evaluation of the rupture characteristics of this great event. The constraint
of the faulting geometry was initially achieved by using information from seismicity, and the focal mechanisms of earthquakes
that occurred during the instrumental period. A rupture model for this great earthquake is constructed by assuming an elastic
medium and calculating the theoretical surface displacements for various fault models that are matched with the observed surface
deformation gleaned from historical reports. The resulted fault model concerns thrust faulting with a rupture length of 160
km and a seismic moment of 5.7 × 1028 dyn·cm, an average slip of 8.9 m and a corresponding moment magnitude equal to 8.4, in excellent agreement with the macroseismic
estimation. The absence of such events recurrence is an indication of the lack of complete seismic coupling that is common
in subduction zones, which is in accordance with the back arc spreading of the Aegean microplate and with previous results
showing low coupling for extensional strain of the upper plate. 相似文献
55.
Seismic Hazard Evaluation in Western Turkey as Revealed by Stress Transfer and Time-dependent Probability Calculations 总被引:1,自引:0,他引:1
P. M. Paradisopoulou E. E. Papadimitriou V. G. Karakostas T. Taymaz A. Kilias S. Yolsal 《Pure and Applied Geophysics》2010,167(8-9):1013-1048
Western Turkey has a long history of destructive earthquakes that are responsible for the death of thousands of people and which caused devastating damage to the existing infrastructures, and cultural and historical monuments. The recent earthquakes of Izmit (Kocaeli) on 17 August, 1999 (M w = 7.4) and Düzce (M w = 7.2) on 12 November, 1999, which occurred in the neighboring fault segments along the North Anatolian Fault (NAF), were catastrophic ones for the Marmara region and surroundings in NW Turkey. Stress transfer between the two adjacent fault segments successfully explained the temporal proximity of these events. Similar evidence is also provided from recent studies dealing with successive strong events occurrence along the NAF and parts of the Aegean Sea; in that changes in the stress field due to the coseismic displacement of the stronger events influence the occurrence of the next events of comparable size by advancing their occurrence time and delimiting their occurrence place. In the present study the evolution of the stress field since the beginning of the twentieth century in the territory of the eastern Aegean Sea and western Turkey is examined, in an attempt to test whether the history of cumulative changes in stress can explain the spatial and temporal occurrence patterns of large earthquakes in this area. Coulomb stress changes are calculated assuming that earthquakes can be modeled as static dislocations in elastic half space, taking into account both the coseismic slip in large (M ≥ 6.5) earthquakes and the slow tectonic stress buildup along the major fault segments. The stress change calculations were performed for strike-slip and normal faults. In each stage of the evolutionary model the stress field is calculated according to the strike, dip, and rake angles of the next large event, whose triggering is inspected, and the possible sites for future strong earthquakes can be assessed. A new insight on the evaluation of future seismic hazards is given by translating the calculated stress changes into earthquake probability using an earthquake nucleation constitutive relation, which includes permanent and transient effects of the sudden stress changes. 相似文献
56.
Least-Squares Wavelet Analysis of Unequally Spaced and Non-stationary Time Series and Its Applications 总被引:1,自引:0,他引:1
Least-squares spectral analysis, an alternative to the classical Fourier transform, is a method of analyzing unequally spaced and non-stationary time series in their first and second statistical moments. However, when a time series has components with low or high amplitude and frequency variability over time, it is not appropriate to use either the least-squares spectral analysis or Fourier transform. On the other hand, the classical short-time Fourier transform and the continuous wavelet transform do not consider the covariance matrix associated with a time series nor do they consider trends or datum shifts. Moreover, they are not defined for unequally spaced time series. A new method of analyzing time series, namely, the least-squares wavelet analysis is introduced, which is a natural extension of the least-squares spectral analysis. This method decomposes a time series to the time–frequency domain and obtains its spectrogram. In addition, the probability distribution function of the spectrogram is derived that identifies statistically significant peaks. The least-squares wavelet analysis can analyze any non-stationary and unequally spaced time series with components of low or high amplitude and frequency variability, including datum shifts, trends, and constituents of known forms, by taking into account the covariance matrix associated with the time series. The outstanding performance of the proposed method on synthetic time series and a very long baseline interferometry series is demonstrated, and the results are compared with the weighted wavelet Z-transform. 相似文献
57.
B.C. Papazachos V.G. Karakostas A.A. Kiratzi B.N. Margaris C.B. Papazachos E.M. Scordilis 《Journal of Seismology》2002,6(4):557-570
Instrumental magnitudes in Greece have been reported as: a) Mmagnitudes based on the records of the Wiechert or Mainka seismographs,b) MLGR magnitudes based on the records of the Wood-Anderson(WA) seismographs (To = 0.8 sec, Veffective 1000) or othershort period seismographs calibrated against WA records and,c) MLSM magnitudes based on strong motion records(accelerograms). Comparison of such magnitudes with momentmagnitudes, Mw, for 329 earthquakes, with epicenters in thebroader Aegean area, performed in this study, showedthat M, MLGR+0.5 and MLSM are practically equalto Mw, with a small overall standard error ( = 0.23).Therefore, equivalent moment magnitudes, Mw
*,estimated from these magnitudes and reported in the catalogues of theGeophysical Laboratory of the University of Thessaloniki are equal tomoment magnitudes for all practical purposes with reasonable uncertainties.It has been further shown that surface wave magnitudes, Ms,for Ms <6.0, can be also transferred into momentmagnitudes, Mw
*, but the larger uncertaintiesencountered make its use rather problematic. 相似文献
58.
E. Papadimitriou V. Karakostas M. Tranos B. Ranguelov D. Gospodinov 《International Journal of Earth Sciences》2007,96(5):911-924
Activation of major faults in Bulgaria and northern Greece presents significant seismic hazard because of their proximity
to populated centers. The long recurrence intervals, of the order of several hundred years as suggested by previous investigations,
imply that the twentieth century activation along the southern boundary of the sub-Balkan graben system, is probably associated
with stress transfer among neighbouring faults or fault segments. Fault interaction is investigated through elastic stress
transfer among strong main shocks (M ≥ 6.0), and in three cases their foreshocks, which ruptured distinct or adjacent normal fault segments. We compute stress
perturbations caused by earthquake dislocations in a homogeneous half-space. The stress change calculations were performed
for faults of strike, dip, and rake appropriate to the strong events. We explore the interaction between normal faults in
the study area by resolving changes of Coulomb failure function (ΔCFF) since 1904 and hence the evolution of the stress field in the area during the last 100 years. Coulomb stress changes were
calculated assuming that earthquakes can be modeled as static dislocations in an elastic half-space, and taking into account
both the coseismic slip in strong earthquakes and the slow tectonic stress buildup associated with major fault segments. We
evaluate if these stress changes brought a given strong earthquake closer to, or sent it farther from, failure. Our modeling
results show that the generation of each strong event enhanced the Coulomb stress on along-strike neighbors and reduced the
stress on parallel normal faults. We extend the stress calculations up to present and provide an assessment for future seismic
hazard by identifying possible sites of impending strong earthquakes. 相似文献
59.
Application of the stress evolutionary model along the Xiaojiang fault zone in Yunnan Province,Southeast China 总被引:1,自引:0,他引:1
Parthena M. Paradisopoulou Charikleia G. Garlaouni Xueshen Jin Eleftheria E. Papadimitriou Vasileios G. Karakostas Jialiang Yang 《Acta Geophysica》2007,55(4):577-593
The Xiaojiang fault zone constitutes part of the major Xianshuihe-Xiaojiang left lateral structure that bounds the rhombic-shaped
block of Yunnan-Sichuan to the east. Long strike slip fault zones that have repeatedly accommodated intense seismic activity,
constitute a basic feature of southeast China. Known historical earthquakes to have struck the study area are the 1713 Xundian
of M6.8, 1725 Wanshou mountain of M6.8, the 1733 Dongchuan of M7.8, and the strongest one, the 1833 Songming of M8.0. Although instrumental record did not report events of this magnitude class, the 18th century clustering as well as the
19th century large event prompted the investigation of stress transfer along this fault zone. Coulomb stress changes were
calculated assuming that earthquakes can be modeled as static dislocations in an elastic half-space, and taking into account
both the coseismic slip in strong (M ≥ 6.8) earthquakes and the slow tectonic stress buildup along the major fault segments. Geological and geodetic data are
used to infer the geometry of these faults and long term slip rates on them, as well as for the fault segments that slipped.
Evidence is presented that the strong historical events as well as the ones of smaller magnitude that occurred during the
instrumental era, are located in areas where the static stress was enhanced. By extending the calculations up to present,
possible sites for future strong events are identified. 相似文献
60.
Spiros Karakostas Dimitrios Economou 《International journal of geographical information science》2014,28(1):83-103
A new approach for treating multi-objective spatial optimization problems is introduced in this study, aiming at deriving the optimal spatial allocation of Wind Farms on a Greek Island (Lesvos). This work builds on the knowledge gained from numerous applications of multi-objective genetic algorithms, either for spatial planning purposes or for other engineering-related topics, by incorporating modified genetic operators and sophisticated planning criteria. Hence, a stand-alone genetic optimizer was developed that incorporates the controlled non-dominated sorting genetic algorithm-II (CNSGA-II), in which the user can model all planning criteria and constraints for every spatial entity to be allocated, and handle the genetic solver via a built-in computational framework that permits the analysis of large terrains. The presented paradigm provides interesting findings for the optimal development of renewable energy sources projects whose spatial allocation is governed by conflicting criteria and strict constraints. 相似文献