Preliminary models of upper mantle P and S wave velocity structure in the western South America region |
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| Institution: | 1. 2-16-106, Prashantinagar, Hyderabad 500039, India;2. National Geophysical Research Institute, Hyderabad 500007, India;1. Faculty of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran;2. Department of Ground Engineering and Materials Science, Universidad de Cantabria, Santander, Spain;1. Department of Sociology, Davidson College, Box 7139, Davidson, NC 28035-7011, United States;2. Ringling College of Art and Design, 2700 N Tamiami Trail, Sarasota, FL 34234, United States;1. Institute of Earth Sciences, Faculty of Geosciences and Environment, University of Lausanne, CH-1015 Lausanne, Switzerland;2. Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY, 14627, USA;3. Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA;4. Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI, 48109, USA;5. School of the Environment, Washington State University, Pullman, WA, 99164, USA;1. Department of Vascular Surgery, University of Birmingham, Birmingham, UK;2. Birmingham Clinical Trials Unit, University of Birmingham, Birmingham, UK;1. Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China;2. Beijing Water Sciences and Technology Institute, Beijing, 100048, China;3. Beijing Key Laboratory of Industrial Wastewater Treatment and Reuse, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China;4. State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China |
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| Abstract: | Upper mantle P and S wave velocities in the western South America region are obtained at depths of foci from an analysis of travel time data of deep earthquakes. The inferred velocity models for the Chile–Peru–Ecuador region reveal an increase of P velocity from 8.04 km/s at 40 km to 8.28 km/s at 250 km depth, while the S velocity remains almost constant at 4.62 km/s from 40 to 210 km depth. A velocity discontinuity (probably corresponding to the L discontinuity in the continental upper mantle) at 220–250 km depth for P and 200–220 km depth for S waves, with a 3–4% velocity increase, is inferred from the velocity–depth data. Below this discontinuity, P velocity increases from 8.54 km/s at 250 km to 8.62 km/s at 320 km depth and S velocity increases from 4.81 km/s at 210 km to 4.99 km/s at 290 km depth. Travel time data from deep earthquakes at depths greater than 500 km in the Bolivia–Peru region, reveal P velocities of about 9.65 km/s from 500 to 570 km depth. P velocity–depth data further reveal a velocity discontinuity, either as a sharp boundary at 570 km depth with 8–10% velocity increase or as a broad transition zone with velocity rapidly increasing from 560 to 610 km depth. P velocity increases to 10.75 km/s at 650 km depth. A comparison with the latest global average depth estimates of the 660 km discontinuity reveals that this discontinuity is at a relatively shallow depth in the study region. Further, a velocity discontinuity at about 400 km depth with a 10% velocity increase seems to be consistent with travel time observations from deep earthquakes in this region. |
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