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Institut de Physique du Globe de Paris, Dèpartement de Seismologie, Paris, France
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- PublicationRestrictedSeismicity, deformation and seismic hazard in the western rift of Corinth: New insights from the Corinth Rift Laboratory (CRL)(2006)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;This paper presents the main recent results obtained by the seismological and geophysical monitoring arrays in operation in the rift of Corinth, Greece. The Corinth Rift Laboratory (CRL) is set up near the western end of the rift, where instrumental seismicity and strain rate is highest. The seismicity is clustered between 5 and 10 km, defining an active layer, gently dipping north, on which the main normal faults, mostly dipping north, are rooting. It may be interpreted as a detachment zone, possibly related to the Phyllade thrust nappe. Young, active normal faults connecting the Aigion to the Psathopyrgos faults seem to control the spatial distribution of the microseismicity. This seismic activity is interpreted as a seismic creep from GPS measurements, which shows evidence for fast continuous slip on the deepest part on the detachment zone. Offshore, either the shallowest part of the faults is creeping, or the strain is relaxed in the shallow sediments, as inferred from the large NS strain gradient reported by GPS. The predicted subsidence of the central part of the rift is well fitted by the new continuous GPS measurements. The location of shallow earthquakes (between 5 and 3.5 km in depth) recorded on the on-shore Helike and Aigion faults are compatible with 50° and 60° mean dip angles, respectively. The offshore faults also show indirect evidence for high dip angles. This strongly differs from the low dip values reported for active faults more to the east of the rift, suggesting a significant structural or rheological change, possibly related to the hypothetical presence of the Phyllade nappe. Large seismic swarms, lasting weeks to months, seem to activate recent synrift as well as pre-rift faults. Most of the faults of the investigated area are in their latest part of cycle, so that the probability of at least one moderate to large earthquake (M = 6 to 6.7) is very high within a few decades. Furthermore, the region west to Aigion is likely to be in an accelerated state of extension, possibly 2 to 3 times its mean interseismic value. High resolution strain measurement, with a borehole dilatometer and long base hydrostatic tiltmeters, started end of 2002. A transient strain has been recorded by the dilatometer, lasting one hour, coincident with a local magnitude 3.7 earthquake. It is most probably associated with a slow slip event of magnitude around 5 ± 0.5. The pore pressure data from the 1 km deep AIG10 borehole, crossing the Aigion fault at depth, shows a 1 MPa overpressure and a large sensitivity to crustal strain changes.77 1 - PublicationOpen AccessDetails of the rupture Kinematics and mechanism of the 1980 Irpinai earthquake: new results and remaining questions(1993)
; ; ; ; ;Bernard, P.; Institute de Physique du Globe de Paris, France ;Zollo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Trifu, C.I.; Center of Earth Physics and Seismology, Bucharest, Romania ;Herrero, A.; Institute de Physique du Globe de Paris, France; ; ; 188 183 - PublicationOpen AccessCrustal structure of the Gulf of Corinth in Central Greece, determined from magnetotelluric soundings(1997-01)
; ; ; ; ; ;Chouliaras, G.; National Observatory of Athens, Institute of Geodynamics, Athens, Greece ;Pham, V. N.; Institut de Physique du Globe de Paris, Laboratoire de Geomagnetisme, Paris, France ;Boyer, D.; Institut de Physique du Globe de Paris, Laboratoire de Geomagnetisme, Paris, France ;Bernard, P.; Institut de Physique du Globe de Paris, Dèpartement de Seismologie, Paris, France ;Stavrakakis, G. N.; National Observatory of Athens, Institute of Geodynamics, Athens, Greece; ; ; ; The magnetotelluric sounding method at 15 sites was employed to investigate the electrical properties of the crust and upper mantle near the epicentral region of the June 15 1995, Ms = 6.1, destructive earthquake in the Gulf of Corinth, Central Greece. The magnetotelluric results indicate the presence of a conductive zone in the mid-crust at a depth of 9 to 12 km near the seismogenetic region. The existence of this zone with a thickness of around 7 km can be explained by the presence of fluids in a zone of ductile shear. A second electrical discontinuity was also found at a depth of about 28 km and this may well correspond to the Moho below the Gulf of Corinth.137 137 - PublicationOpen AccessSlip heterogeneity, body-wave spectra, and directivity of earthquake ruptures(1994-12)
; ; ;Bernard, P.; Département de Sismologie, I.P.G.P., Paris, France ;Herrero, A.; Département de Sismologie, I.P.G.P., Paris, France; We present a broadband kinematic model based on a self-similar k-square distribution of the coseismic slip, with an instantaneous rise-time and a constant rupture velocity. The phase of the slip spectrum at high wave number is random. This model generates an ?-squared body-wave radiation, and a particular directivity factor C2d scaling the amplitude of the body-wave spectra, where Cd is the standard directivity factor. Considering the source models with a propagating pulse and a finite rise-time, we assume that within the slipping band, the rupture has some random character, with small scale rupture in various directions. With such a model, the pulse cannot be resolved, and the directivity factor is still C2d at low frequency; at periods shorter than the rise-time, however, the directivity effect drops to much smaller rms values. This frequency dependent directivity effect, which is expected to be the strongest for sites located in the direction of rupture, was evidenced for the Landers 1992 earthquake, leading to a 2 to 3 s rise-time of the slip pulse. This kinematic model can be used with more refined theoretical Green's functions, including near-field terms and surface waves, or with empirical Green's functions, for generating realistic broadband records in the vicinity of moderate to large earthquakes, in a frequency range relevant for engineering applications (0 Hz to about 20 Hz).123 378