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| Titel |
Seismic Travel-Time Tomography of the Northern Andean Volcanic Zone in Ecuador |
| VerfasserIn |
Sebastián Araujo, Bernard Valette, Vadim Monteiller, Mario Ruiz |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096586
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| Publikation (Nr.) |
 EGU/EGU2014-12096.pdf |
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| Zusammenfassung |
| In this poster we present the results of an inversion of earthquakes travel-time data recorded
by the national Ecuadorian network. We aim to identify the topography of the slab, to
ascertain the velocity of P and S waves, as well as to locate more accurately events in the
mantle and the crust beneath Ecuador. The data catalog of the Institute of Geophysics of
Quito consists of 478,000 P and S phases corresponding to 21,152 events recorded
between 1988 and 2012 by the national network. It provides a unique opportunity
to improve our information on the lithospheric structure and the topology of the
slab.
The domain within which the velocity model is searched for consists of a box oriented in
the main direction of the trench and of the Andes Cordillera, taking account of the Earth’s
ellipticity, in addition to the surface topography. An a priori model of the Moho
depth was first determined by matching together informations coming from global
gravitational potential, wide-angle reflection seismics and bathymetry studies in the coastal
area.
The inversion is performed through a non-linear least-square approach based on a
stochastic description of data and model. The forward computation of time delay is
performed by integrating slowness along the rays, which are determined by the
Podvin-Lecomte algorithm which is based on a finite difference resolution of the eikonal
equation. The regularization of the velocity fields is achieved through a covariance norm on
P velocity and V P-V S velocity ratio over the box domain, with an exponential type kernel.
The tuning of smoothing and damping parameters is carried out through an L-curve
analysis.
The topography of the slab, as displayed by the seismicity, presents an increasing dip
from north to south, with a deep cluster of seismicity in the 1.5°- 2°S latitude range. |
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