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Audrey Gailler Philippe Charvis Ernst R. Flueh 《Earth and Planetary Science Letters》2007,260(3-4):444-464
We describe the deep structure of the south Colombian–northern Ecuador convergent margin using travel time inversion of wide-angle seismic data recently collected offshore. The margin appears segmented into three contrasting zones. In the North Zone, affected by four great subduction earthquakes during the 20th century, normal oceanic crust subducts beneath the oceanic Cretaceous substratum of the margin underlined by seismic velocities as high as 6.0–6.5 km/s. In the Central Zone the subducting oceanic crust is over-thickened beneath the Carnegie Ridge. A steeper slope and a well-developed, high velocity, Cretaceous oceanic basement characterizes the margin wedge. This area coincides with a gap in significant subduction earthquake activity. In the South Zone, the subducting oceanic crust is normal. The fore-arc is characterized by large sedimentary basins suggesting significant subsidence. Velocities in the margin wedge are significantly lower and denote a different nature or a higher degree of fracturing.
Even if the distance between the three profiles exceeds 150 km, the structural segmentation obtained along the Ecuadorian margin correlates well with the distribution of seismic activity and the neotectonic zonation. 相似文献
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Cordrie Louise Gailler Audrey Escartin Javier Feuillet Nathalie Heinrich Philippe 《Natural Hazards》2020,103(2):2103-2129
Natural Hazards - The arc of the Lesser Antilles is associated with a significant tectonic activity due to the subduction of the Atlantic oceanic plate under the Caribbean plate. Earthquakes in... 相似文献
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Audray Delcamp Benjamin van Wyk de Vries Mike R. James L. S. Gailler E. Lebas 《Bulletin of Volcanology》2012,74(3):743-765
Volcano spreading, with its characteristic sector grabens, is caused by outward flow of weak substrata due to gravitational
loading. This process is now known to affect many present-day edifices. A volcano intrusive complex can form an important
component of an edifice and may induce deformation while it develops. Such intrusions are clearly observed in ancient eroded
volcanoes, like the Scottish Palaeocene centres, or in geophysical studies such as in La Réunion, or inferred from large calderas,
such as in Hawaii, the Canaries or Galapagos volcanoes. Volcano gravitational spreading and intrusive complex emplacement
may act simultaneously within an edifice. We explore the coupling and interactions between these two processes. We use scaled
analogue models, where an intrusive complex made of Golden syrup is emplaced within a granular model volcano based on a substratum
of a ductile silicone layer overlain by a brittle granular layer. We model specifically the large intrusive complex growth
and do not model small-scale and short-lived events, such as dyke intrusion, that develop above the intrusive complex. The
models show that the intrusive complex develops in continual competition between upward bulging and lateral gravity spreading.
The brittle substratum strongly controls the deformation style, the intrusion shape and also controls the balance between
intrusive complex spreading and ductile layer-related gravitational spreading. In the models, intrusive complex emplacement
and spreading produce similar structures to those formed during volcano gravitational spreading alone (i.e. grabens, folds,
en échelon fractures). Therefore, simple analysis of fault geometry and fault kinetic indicators is not sufficient to distinguish
gravitational from intrusive complex spreading, except when the intrusive complex is eccentric from the volcano centre. However,
the displacement fields obtained for (1) a solely gravitational spreading volcano and for (2) a gravitational spreading volcano
with a growing and spreading intrusive complex are very different. Consequently, deformation fields (like those obtained from
geodetic monitoring) can give a strong indication of the presence of a spreading intrusive complex. We compare the models
with field observations and geophysical evidence on active volcanoes such as La Réunion Island (Indian Ocean), Ometepe Island
(Nicaragua) and eroded volcanic remnants such as Ardnamurchan (Scotland) and suggest that a combination between gravitational
and intrusive complex spreading has been active. 相似文献
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We present a synthesis of tide gauge data recorded on June 26–28, 2011, along the NE Atlantic and the English Channel coastlines, which show a significant sea level disturbance observed from Portugal to England during several hours. Though the amplitude was low (a few centimeters at most), the main disturbance was observed in about 30 harbors. The phenomenon started in south Spain and Portugal in the last hours of 26 June and reached the French west coastline on 27 June, at about noon. Finally, it was observed in the English Channel (UK and France) from 27 June to 28 June and also noticed by witnesses as tidal bores in Cornwall. For some of the places investigated, it was followed by a second signal about 12 h later, especially in the SE of the Bay of Biscay. Spectral analyses show a dominant periods of 25 min present on almost all data and that the phenomenon highlighted the resonant periods of the harbors. Using travel time modeling, we observe that the disturbance traveled much more slowly than long-wave propagation and that the timing does not compel with a single source for all the recordings. A comparison with available atmospheric data reveals that a pressure anomaly traveled the same day across the area, from south Portugal to the English Channel and was probably the origin of several sources for the phenomenon, with a second one completing the later signals. Finally, historic facts present that these kinds of event can be potentially lethal or damaging. 相似文献
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Nicole Bethoux Monica Segovia Viviana Alvarez Jean-Yves Collot Philippe Charvis Audrey Gailler Tony Monfret 《Journal of South American Earth Sciences》2011,31(1):139-152
A seismic study of a segment of the convergent margin of Ecuador is presented. During the SISTEUR campaign a network of 24 Ocean Bottom Seismometers (OBS) was deployed on the Carnegie Ridge, one line along the main axes of the ridge and two lines across the strike of the edge of the ridge, during one month. This marine network was complemented with a land network of 20 stations distributed in two lines: one parallel to the margin and the other perpendicular to it.The seismic event recorded by these networks, were located using different crustal models defined from the wide-angle seismic data modeling. Relative location techniques were used to improve earthquake locations. Seismogram waveform modeling allowed us to constrain hypocentral location for events farther than ～50 km from the network. This modeling also provided additional information to constrain the focal mechanisms of these events. The upper limit of the Interplate Seismogenic Zone (ISZ) is estimated to be at a 10 km depth in the region. The background seismic activity of the upper plate provided new insights:1) A seismic cluster that reaches the base of the overriding plate is linked to the Jipijapa-Portoviejo fault. The reactivation of this Quaternary fault is confirmed by focal mechanisms that provide rupture planes parallel to its superficial projection (N10°–N25°).2) The focal mechanisms presented in this study are compatible with a homogeneous regional stress field corresponding to an E–W to ESE–WNW compression and an NNE–SSW extension. The presence of strike-slip deformation, with a reverse component, corresponds to the NNE escape of the North Andean Block. Normal faulting accommodating this movement suggests that this part of the North Andean Block cannot be considered as a rigid block. 相似文献
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