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Geofísica internacional
On-line version ISSN 2954-436XPrint version ISSN 0016-7169
Geofís. Intl vol.44 n.2 Ciudad de México Apr./Jun. 2005
Articles
Elastic thickness of the oceanic lithosphere beneath Tehuantepec ridge
1 Instituto de Geofísica, UNAM, Cd. Universitaria, 04510 México, D.F., Mexico
2 Now in: Seismological Laboratory, 252-21, California Institute of Technology, Pasadena, CA 91125, USA.
3 Centro de Geociencias, Campus UNAM Juriquilla, Apartado Postal 15, Boulevard Villas del Mesón S/N, Juriquilla, 76230 Querétaro, Qro.
Relationship between bathymetry and free-air gravity is analyzed by computing response function (admittance) for 7 shipborne profiles crossing the Tehuantepec ridge (TR). The age of the lithosphere at the time of bathymetric loading of the TR is deduced from the experimental admittance and the elastic thickness, Te. Admittance is interpreted in terms of isotropic elastic plate thick-ness. The oceanic lithosphere is assumed to behave as an elastic plate 10±5 km thick. Low admittances at low wave-numbers suggest that TR is isostatically compensated. We estimate a median value of 8 Ma (in the interval 2-17 Ma) for the age of oceanic lithosphere at the time of TR onset.
KEY WORDS: Tehuantepec ridge; elastic thickness; admittance; gravity modeling
La relación entre la batimetría y la anomalía de gravedad de aire libre se analizó por medio del método de la admitancia para 7 perfiles que cruzan la cordillera de Tehuantepec. La evaluación de la edad de la litosfera para el tiempo cuando se formó la cordillera de Tehuantepec se calculó a través de los análisis de la admitancia experimental y del espesor elástico. Se calculó la admitancia, interpretada en términos del espesor elástico isótropo de la placa de Cocos debajo de la cordillera de Tehuantepec. El modelo de compensación isostática más apropiado para ajustar los datos observados es el de una litosfera oceánica que se comporta como una placa elástica con un espesor de 10±5 km. La forma de la admitancia (con valores bajos para longitudes de onda grandes) sugiere que la cordillera está compensada isostáticamente. La relación entre la edad de la litosfera oceánica y el espesor elástico para una temperatura de corte de 450 °C, da una estimación mediana de 8 Ma (en un intervalo de 2-17 Ma) para el momento de formación de la cordillera de Tehuantepec sobre la placa de Cocos.
PALABRAS CLAVE: Cordillera de Tehuantepec; espesor elástico; admitancia; modelación gravimétrica
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Received: March 23, 2004; Accepted: October 14, 2004
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