Two-phase opening of Andaman Sea: a new seismotectonic insight |
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| Affiliation: | 1. Department of Applied Geophysics, Indian School of Mines, Dhanbad, Jharkhand, India;2. Department of Applied Geology, Indian School of Mines, Dhanbad, Jharkhand, India;1. Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai 4000765, India;2. Department of Geology, University of Delhi, Delhi 110007, India;3. Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India;1. Key Laboratory of Petroleum Resources Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;3. State Key Laboratory of Marine Geology, School of Ocean and Earth Science, Tongji University, Shanghai 200092, China;4. Guangzhou Marine Geological Survey, Guangzhou 510760, China;5. Departamento de Geociências and CESAM, Universidade de Aveiro, Aveiro 3800, Portugal;1. Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA;2. CSIR-National Institute of Oceanography, Dona Paula, Goa, India;3. CNRS/LEGOS, Toulouse, France;4. LOCEAN, IPSL, Sorbonne Universités (UPMC, Univ. Paris 06)/CNRS/IRD/MNHN, Paris, France;5. Indo-French Cell for Water Sciences, IISc-NIO-IITM–IRD Joint International Laboratory, NIO, Goa, India;1. Graduate School of Environmental Studies, Nagoya University, Nagoya, Japan;2. International Institute of Seismology and Earthquake Engineering, Ibaraki, Japan;3. Department of Applied Science, Kochi University, Akebono-cho, Japan;4. Tono Research Institute of Earthquake Science, Mizunami, Japan;5. Graduate Research on Earthquake and Active Tectonics, Bandung Institute of Technology, Indonesia;6. Graduate School of Science, Tohoku University, Sendai, Japan;7. Department of Physics, Syiah Kuala University, Banda Aceh, Indonesia;8. Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Indonesia;1. National Energy Technology Laboratory, U.S. Department of Energy, Albany, OR 97321, USA;2. College of Earth, Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 7331, USA;3. Department of Earth Science, University of New Hampshire, Durham, NH 03824, USA;4. Department of Geology and Geophysics, Woods Hole Oceanographic Institute, Woods Hole, MA 02543, USA;5. School of Oceanography, University of Washington, Seattle, WA 98195, USA;6. Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093-0212, USA;7. Lawrence Berkley National Laboratory, Berkeley, CA 94720, USA;8. Pacific Northwest National Laboratory, Richland, WA 99352, USA |
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| Abstract: | High-resolution reconstruction of Benioff zone depth–dip angle trajectory for Burma–Java subduction margin between 2° and 17°N Lat. reveals two major episodes of plate geometry change expressed as abrupt deviation in subduction angle. Estimation of effective rate of subduction in different time slices (and then length of subducted slab) allowed drawing of isochrones in Ma interval through these trajectories for the time period 5–12 Ma. With these isochrones, the deformation events on the subducting Indian plate are constrained in time as of 4–5 and 11 Ma old. This well-constrained time connotation offered scope for the correlation of slab deformation events with the well-established two-phase opening history of the Andaman Sea. While the 11 Ma event recorded from southern part of the study area is correlated with early stretching and rifting phase, the 4–5 Ma event is interpreted as major forcing behind the spreading phase of the Andaman Sea. Systematic spatio-temporal evaluation of Indian plate obliquity on the Andaman Sea evolution shows its definite control on the early rifting phase, initiated towards south near northwest Sumatra. The much young spreading phase recorded towards north of 7° Lat. is possibly the result of late Miocene–Pliocene trench retreat and follow-up transcurrent movement (along Sagaing and Sumatran fault system) with NW–SE pull-apart extension.Nonconformity between plate shape and subduction margin geometry is interpreted as the causative force behind Mid-Miocene intraplate extension and tearing. Enhanced stretching in the overriding plate consequently caused active forearc subsidence, recorded all along this plate margin. Initial phase of the Andaman Sea opening presumably remains concealed in this early–middle Miocene forearc subsidence history. The late Miocene–Pliocene pull-apart opening and spreading was possibly initiated near the western part of the Mergui–Sumatra region and propagated northward in subsequent period. A temporary halt in rifting at this pull-apart stage and northeastward veering of the Andaman Sea Ridge (ASR) are related with uplifting of oceanic crust in post-middle Miocene time in form of Alcock and Sewell seamounts, lying symmetrically north and south of this spreading ridge. |
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