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  • 1
    Electronic Resource
    Electronic Resource
    Coseismic crustal deformation from microseismicity in the Patras area, western Greece (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 122 (1995), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The Patras area lies in the western part of central Greece. It is an area characterized by high seismicity and complex neotectonics. Several devastating earthquakes have occurred in the region since 600 BC. Contemporary crustal deformation is examined in this area using microearthquake data recorded over a lengthy period, during 1983–84, by the Patras Seismic Network, principally, and to a lesser extent by the Volos Seismic Network.The microseismicity (1.8–3.9 ML) defines a zone deepening to the NE, which justifies a possible extension of the Gulf of Corinth major graben towards the Trikhonis Lake to the NW.Spectra of 108 well-located microearthquakes are estimated, using P-waves obtained by selective windowing designed to include only the P-phase; seismic moments in the range 0.3–45.7 × 1012 Nm are obtained, accompanied by estimates of seismotectonic source parameters including source radii, average stress drop and average coseismic slip.Poor correlation is found between seismic moment and magnitude, and the likely reason is the complex nature of the neotectonic regime existing in the area.Two zones differing in crustal deformation characteristics are observed. The Corinth-Trikhonis zone reveals two sets of characteristic faults. The first set is represented by microearthquakes showing distinctive and relatively higher seismic moments in conjunction with lower stress drops and seismic slips. This set of faults shows greater source radius than the second set, and therefore the faults are longer. The second set is characterized by an almost constant source radius within the range of uncertainty, and a wide range of seismic moments, stress drops and seismic slips. The Rio zone is characterized by low seismic slip, stress drop and fault radii, with the exception of the locality south of the city of Patras, where relatively higher seismic slip, stress drop and fault radius are observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1995.tb06840.x
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  • 2
    Electronic Resource
    Electronic Resource
    Seismotectonics and the earthquake frequency–magnitude distribution in the Aegean area (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 98 (1989), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A study of Aegean seismotectonics and the resulting frequency–magnitude distribution on a broad scale is undertaken, using the tectonic model of Le Pichon & Angelier. This implies a tectonic moment release rate due to the spreading of the Aegean of 17 ± 8 times 1018 N m-1 yr-1 over the past 13 Ma, if stretching is due mainly to a series of normal faults dipping at about 45° in a seismogenic crust 10–20 km deep. The moment-magnitude relation from an instrumental magnitude catalogue is log M0=A+Bm, with A= 10.970 ± 0.294, B= 1.206 in SI units. This is established from 50 events of magnitude Ms〉5.3 whose scalar seismic moments M0 have been evaluated in a homogeneous manner for the region by spectral analysis of surface waves at 30–60 s period. By contrast published body-wave analyses, from waveform modelling at 20 s period and moment tensor analyses seem to produce seismic moments which are lower by a factor of two or so on average. This moment–magnitude relation implies a seismogenic moment release rate due to stretching in the Aegean of 14 times 1018 N m-1 yr-1 during the time period 1918–81 and 17 times 1018 N m-1 yr-1 for the period 1964–81, within a factor of two or so uncertainty. This implies that the energy release in the brittle crust due to Aegean spreading is substantially seismic within the stated accuracy, and is also relatively stationary even when compared with the tectonic moment release rates. A similar comparison using the same tectonic model shows that the subducting slab is sinking beneath the Hellenic arc almost completely aseismically, and that processes such as near vertical slab pull and confined thermal expansion could explain most of the observed seismic energy release by internal deformation of the slab. The frequency–magnitude statistics for the area of active extension has a characteristic earthquake of magnitude 7Ms, corresponding approximately to fault depths of 10–14 km for an aspect ratio of 2 and a strain drop of 10-4. This is close to the observed seismogenic depth (10–20 km) for well-determined earthquakes in the Aegean area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1989.tb02291.x
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  • 3
    Electronic Resource
    Electronic Resource
    Coseismic crustal deformation on a fault zone defined by microseismicity in the Pavliani area, central Greece (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 123 (1995), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Pavliani is an area of high microseismicity in northern central Greece. There is no evidence in the historical record of large damaging earthquakes in this area since at least 600 BC. We examine contemporary crustal deformation in this area using microearthquake data recorded during 1983–84 by the Volos seismic network, principally, and to a lesser extent by the Patras seismic network.The microseismicity (1–4.6 ML) defines an approximately vertical fault zone trending WSW-ENE, of 55 km length and 25 km depth. the fault-plane solution for the 4.6 ML earthquake shows a strike consistent with the trend of the microseismicity zone, and an extension direction consistent with many large earthquakes in central Greece associated with the extensional greater Aegean. Spectra of the microearthquakes are estimated using P waves obtained by selective windowing designed to exclude other P phases from the coda; seismic moments in the range 1–95 x 1012 N m are obtained, accompanied by estimates of seismotectonic source parameters, including source radii, average stress drop and average coseismic slip. of prime utility is an excellent correlation found between seismic moment and magnitude, and with coseismic slip. This allows heterogeneity in the distribution of individual microearthquake source parameters to be mapped onto the vertical fault-zone plane and the history of coseismic deformation for the whole seismicity observed during 1983–84 to be examined using cumulative slip and moment-release rate. Peaks of high moment-release rate occur in the east and centre of the fault zone. That in the east is dominated by a few large moment-release events; that in the centre by a large number of small events. Both moment-release-rate peaks, despite their different component seismicity, are associated with high cumulative coseismic slip. Only the eastern peak is also associated with high stress drop; it is also shallower, and therefore any surficial interaction is less likely to be attenuated. the surface projection of this peak is within 3 km of a mapped normal fault coincident with an Alpine thrust front delineated by a major scarp of Mesozoic limestone. Surface evidence of recent movement on this normal fault is only slight. Friable fault gouge is seen at a few localities. Displacement could not be determined because the limestone surfaces are deeply weathered and lack kinematic indicators. However, considering the whole fault zone as a cohesive entity, and using a Brune estimate of slip at the current moment-release rate throughout the present extensional tectonic regime, suggests a total vertical displacement of order 175 m, similar to the elevation of the scarp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1995.tb06659.x
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  • 4
    Electronic Resource
    Electronic Resource
    Seismicity in the Hellenic Volcanic Arc: relation between seismic parameters and the geophysical fields in the region (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 117 (1994), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A study of the spatial distribution of seismicity and seismic hazard and geophysical parameters is undertaken along the Hellenic Volcanic Arc (HVA). Seismicity of the area is divided in a cellular manner allowing analysis of the localized seismicity parameters and representation of their regional variation as contour maps. Extreme value analysis locates a zone of highest seismicity just west of centre of the HVA, around the Cyclades Islands. Non-probabilistic modelling of the strain energy release process in terms of magnitudes equivalent to the average annual energy release rate (M2) and the maximum possible energy release in a seismic cycle (M3) enhances this picture. Maximum values of M2 and M3 are more tightly localized in the central Cyclades west of Amorgos Island and also in the east of the HVA in the Sporadhes north-west of Rhodes. Isocyclic contours of the waiting times for M3 show values in excess of 70 years in the Cyclades and eastern Sporadhes, i.e. the zones of largest earthquakes show the longest strain accumulation periods. The waiting time for the HVA as a whole is about 54 years, and at present it appears to be about 75 per cent through to accumulation of the notional maximum strain energy. The b value of the magnitude–frequency distribution shows a consistent spatial variation along the HVA which is not sensitive to subdivision into different focal depth ranges. Regional contour maps of the b values, and maps of local values of heat flow, magnetic and electrical anomalies compared with the Bouguer gravity anomaly map, indicate correlations which reflect the deformation of the Aegean shallow crust in relation to the deep intrusive magmatic processes. The correlations between the different geophysical fields are displaced commensurate with an Aegean extension of approximately 45 km.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1994.tb02462.x
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  • 5
    Electronic Resource
    Electronic Resource
    Shear-Wave Velocity Models From Rayleigh-Wave Dispersion In the Broader Aegean Area (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 125 (1996), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: An analysis of Rayleigh waves generated by earthquakes in the broader Aegean is undertaken to estimate variations in the shear-wave velocity structure in the crust and upper mantle down to about 70 km depth. The study centres literally on the vertical-component long-period standard seismograph at Athens (ATH), and is only possible because this station has provided good-quality data over many years of continuous operation. Rayleigh waves from 81 earthquakes during 1963–87, with surface-wave magnitudes in the range 4.2 to 5.4 and epicentral distances of 300–500 km from Athens are analysed. These earthquake epicentres are selected in clusters defining 12 propagation paths across the broader Aegean and radial to Athens. The highest concentration of azimuthal sampling traverses the Hellenic Volcanic Arc. The ensuing group-velocity curves over these radial paths are inverted to shear-wave velocity-depth models using linear and then Monte Carlo Hedgehog inversion schemes. The resulting velocity-depth solutions from both schemes, presented as individual path velocity-depth profiles, 3-D azimuthal perspectives and contoured velocity-depth panoramas over the whole broader Aegean, are corroborative. The western arc of azimuths extending from Chalkidiki, north of Athens, to SW Crete, south of Athens, have velocity-depth profiles which consistently reach sub-Moho velocities at about 45 km depth. The most striking feature revealed by the contoured shear-wave velocity-depth panoramas is an extensive zone of relatively low velocity, about 3.8 km s−1, centred around 30 km depth, which may extend from 20 to 40 km depth. This low-velocity zone is contained in the wedge of paths from Carpathos, Rhodes and SW Turkey which traverse the Hellenic Volcanic Arc and subtend an angle of about 33° at Athens. There is also slight evidence for anomalously low velocities at greater depths (around 4.1–4.2 km s−1 at about 50–60 km depth) but these are at the limits of useful resolution of the available data; nevertheless, these indications are at their strongest in the same wedge below the Hellenic Volcanic Arc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1996.tb06016.x
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  • 6
    Electronic Resource
    Electronic Resource
    Geophysics: Is there coherence between Earth tides and earthquakes? (1986)
    [s.l.] : Nature Publishing Group
    Nature 321 (1986), S. 115-115 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Do tides in the Earth cause earthquakes? Are some types of earthquakes or regions of the Earth more susceptible to earthquakes triggered by tides than others? And is this relevant to the prediction of earthquakes? There has not yet been much success in answering these questions, although the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/321115a0
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  • 7
    Electronic Resource
    Electronic Resource
    Geophysics: Electrical earthquake prediction (1985)
    [s.l.] : Nature Publishing Group
    Nature 315 (1985), S. 370-371 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Two thousand years ago, Aristotle proposed that earthquakes were caused by subterranean winds. The Greeks are still active in the often contentious business of earthquake prediction and the team of P. Varotsos, K. Alexopoulos and K. Nomicos are well aware of controversy surrounding their work. In ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/315370a0
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  • 8
    Electronic Resource
    Electronic Resource
    Seismic risk of circum-Pacific earthquakes: II. Extreme values using Gumbel's third distribution and the relationship with strain energy release (1985)
    Springer
    Pure and applied geophysics 123 (1985), S. 849-869 
    Details
    ISSN: 1420-9136
    Keywords: Seismic risk ; extreme values ; strain energy ; circum-Pacific
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract In a previous paper (Makropoulos andBurton, 1983) the seismic risk of the circum-Pacific belt was examined using a ‘whole process’ technique reduced to three representative parameters related to the physical release of strain energy, these are:M 1, the annual modal magnitude determined using the Gutenberg-Richter relationship;M 2, the magnitude equivalent to the total strain energy release rate per annum, andM 3, the upper bound magnitude equivalent to the maximum strain energy release in a region. The risk analysis is extended here using the ‘part process’ statistical model of Gumbel's IIIrd asymptotic distribution of extreme values. The circum-Pacific is chosen being a complete earthquake data set, and the stability postulate on which asymptotic distributions of extremes are deduced to give similar results to those obtained from ‘whole process’ or exact distributions of extremes is successfully checked. Additionally, when Gumbel III asymptotic distribution curve fitting is compared with Gumbel I using reduced chi-squared it is seen to be preferable in all cases and it also allows extensions to an upper-bounded range of magnitude occurrences. Examining the regional seismicity generates several seismic risk results, for example, the annual mode for all regions is greater thanm(1)=7.0, with the maximum being in the Japan, Kurile, Kamchatka region atm(1)=7.6. Overall, the most hazardous areas are situated in this northwestern region and also diagonally opposite in the southeastern circum-Pacific. Relationships are established between the Gumbel III parameters and quantitiesm 1(1),X 2 and ω, quantities notionally similar toM 1,M 2 andM 3 although ω is shown to be systematically larger thanM; thereby giving a physical link through strain energy release to seismic risk statistics. Inall regions of the circum-Pacific similar results are obtained forM 1,M 2 andM 3 and the notionally corresponding statistical quantitiesm 1(1),X 2 and ω, demonstrating that the relationships obtained are valid over a wide range of seismotectonic enviroments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876974
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  • 9
    Electronic Resource
    Electronic Resource
    Pathways to seismic hazard evaluation: Extreme and characteristic earthquakes in areas of low and high seismicity (1990)
    Springer
    Natural hazards 3 (1990), S. 275-291 
    Details
    ISSN: 1573-0840
    Keywords: Seismic hazard ; design earthquake ; seismic ground loading ; earthquake perceptibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The general philosophy of seismic hazard evaluation described here is appropriate for selection of seismic input to regional earthquake engineering codes prior to detailed on-site inspections and geotechnical assessments. Some probabilistic seismic hazard methodologies which can be applied in areas of low and high seismicity, are briefly described to emphasise the main equations with specimen results. Three aspects of hazard assessment are explored by different ‘pathways’. These include the analysis of regional earthquake catalogues to obtain magnitude recurrence, particularly using Gumbel extreme value statistics. This is extended to assess ground shaking hazard which is usually sought by earthquake engineers. Thirdly, the concept of earthquake perceptibility is developed, leading to the identification of an earthquake magnitude or type which is characteristic of a region. This ‘most perceptible’ earthquake is most likely to be felt at any site in a region and provides an earthquake selection criterion which can be used in aseismic design of noncritical structures. Because there are several methods of seismic hazard evaluation, the view is expressed that it is sensible for practical purposes to seek results from different methods or different pathways to the hazard evaluation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00124583
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  • 10
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    The Muzaffarabad, Pakistan, earthquake of 8 October 2005: surface faulting, environmental effects and macroseismic intensity (2009)
    In:  Geological Society Special Publication 316: 155-172.
    Details
    Publication Date: 2009-06-22
    Description: The Mw 7.6 Muzaffarabad earthquake of 8 October 2005, occurred on a lateral equivalent of the main ramp of the Hymalaia frontal thrust, and is the result of the collision tectonics between the Indian and Eurasian plates. The epicentre was located near the town of Basantkot (Muzaffarabad), and the focal depth was about 13 km. The Muzaffarabad earthquake provides unequivocal evidence about the localization of severe damage, intense ground shaking and secondary environmental effects near the surface expression of the source fault. We analyse its nature, and impact on man-made structures and the physical environment, on the basis of a detailed survey and macroseismic study of the affected areas conducted by the Micro Seismic Studies Programme (MSSP) Team (Ishfaq Ahmad Research Laboratories, Pakistan Atomic Energy Commission) immediately after the mainshock, assisted by a careful review of the subsequent data and literature. In the course of the field survey, the displacement and surface expression of the causative fault, and accompanying secondary environmental effects were observed at a number of places along a capable thrust fault structure. We refer to this structure as the Kashmir Thrust (KT) capable fault following the terminology of local research geologists in Pakistan; the seismological evidence of this structure is already known in the literature as the Indus-Kohistan Seismic Zone. A complex, clearly segmented, at least 112-km-long surface rupture was mapped along the KT. The maximum values of vertical displacement (on the order of 4 to 7 m) were observed mainly between Muzaffarabad and Balakot, along the central segment of the rupture (52 km) associated with maximum slip at depth and a major portion of the energy release. Both the NW Alai segment (38 km) and SE Bagh segment (22 km) are characterized by scattered minor surface ruptures with a few centimetres of displacement, accompanied by extensive surface cracking, landslides and severe damage, concentrated in a narrow belt along the fault trace. A maximum intensity of XI on the Modified Mercalli Intensity (MMI) scale and on the Environmental Seismic Intensity scale (ESI 2007) was recorded in the epicentral area between Muzaffarabad and Balakot. Extremely severe damage and very important secondary environmental effects in the hanging wall adjacent to the trace of the causative fault plane are mainly due to near-fault strong motion and rupture directivity effects. To our knowledge, this is the first study to present field observations over the whole near-field of the earthquake, and to include the intensity map of the entire meizoseismal region.
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