Variations of young oceanic intraplate seismic energy released with relation to lithosphere age. Implications in the East Pacific Rise and its convergence with the Rivera subduction zone
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We have estimated empirical relationships that associate the age of the Pacific oceanic lithosphere with the seismic energy released on both flanks of the East Pacific Rise. The equations found were tested by comparing other empirical equations based on lithospheric age, heat flow, and bathymetric depth published by other authors. The results of this study are consistent for seafloor ages ranging between 1 and 4 Ma throughout three perpendicular cross-sections. These cross-sections are located between the diverging plate boundary of the northern Pacific Ocean up to the subduction zone of western Mexico. Our results allow us to infer the depth of the 1200 °C isotherm underneath the analyzed plates, from the mid-oceanic ridges up to the subduction zones. The distribution of seismic energy released within the limits of the Rivera and Pacific plates shows a gradual decrease from the ridge axis to the oceanic trench. However, an increase of seismic activity is recorded near the Mesoamerican Trench, where the Rivera Plate subducts under the North American Plate at an angle of ~ 46°. This anomaly is a consequence of the convergence, thrust and deepening of the oceanic plate. Due to the homogeneity of this plate, it is possible to infer the projection of isochrones in the subduction zone. Although the thickening of the thermal boundary layer may be estimated from the square root function of the seismic energy, this brittle–ductile transition in the subduction zone deepens exponentially with relation to the computed energy.
KeywordsHeat flow Seismic energy Brittle–ductile transition Mid-oceanic ridge Rivera plate subduction North American plate
We thank the Geophysical Research Group of the Department of Geosciences, Universidad Nacional de Colombia at Bogotá, for supporting this work. We express our gratitude to USGS, ANSS, NOAA, and Global Heat Flow Group for providing datasets used in this paper. Advice, and useful comments were provided by Mario Andres Gutierrez.
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