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| Titel |
Exploring the shallow structure of the San Ramón thrust fault in Santiago, Chile (~33.5° S), using active seismic and electric methods |
| VerfasserIn |
D. Díaz, A. Maksymowicz, G. Vargas, E. Vera, E. Contreras-Reyes, S. Rebolledo |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 5, no. 2 ; Nr. 5, no. 2 (2014-08-26), S.837-849 |
| Datensatznummer |
250115329
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| Publikation (Nr.) |
 copernicus.org/se-5-837-2014.pdf |
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| Zusammenfassung |
| The crustal-scale west-vergent San Ramón thrust fault system, which lies
at the foot of the main Andean Cordillera in central Chile, is a
geologically active structure with manifestations of late Quaternary complex
surface rupture on fault segments along the eastern border of the city of Santiago.
From the comparison of geophysical and geological observations, we assessed
the subsurface structural pattern that affects the sedimentary cover and
rock-substratum topography across fault scarps, which is critical for
evaluating structural models and associated seismic hazard along the related
faults. We performed seismic profiles with an average length of 250 m, using
an array of 24 geophones (Geode), with 25 shots per profile, to
produce high-resolution seismic tomography to aid in interpreting impedance
changes associated with the deformed sedimentary cover. The recorded
travel-time refractions and reflections were jointly inverted by using a 2-D
tomographic approach, which resulted in variations across the scarp axis in
both the velocities and the reflections that are interpreted as the sedimentary
cover-rock substratum topography. Seismic anisotropy observed from
tomographic profiles is consistent with sediment deformation triggered by
west-vergent thrust tectonics along the fault. Electrical soundings crossing
two fault scarps were used to construct subsurface resistivity tomographic
profiles, which reveal systematic differences between lower resistivity
values in the hanging wall with respect to the footwall of the geological
structure, and clearly show well-defined east-dipping resistivity
boundaries. These boundaries can be interpreted in terms of structurally
driven fluid content change between the hanging wall and the footwall of the
San Ramón fault. The overall results are consistent with a west-vergent
thrust structure dipping ~55° E in the
subsurface beneath the piedmont sediments, with local complexities likely
associated with variations in fault surface rupture propagation,
fault splays and fault segment transfer zones. |
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