Imperial College London
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Emeritus ProfessorLidiaLonergan

Faculty of Engineering, Department of Earth Science & Engineering

Emeritus Reader of Geotectonics
 
 
 
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Contact

 

+44 (0)20 7594 6465l.lonergan Website

 
 
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Location

 

3.48Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@inproceedings{Lonergan:2019,
author = {Lonergan, L and Collier, J and McDermott, C and Fruehen, J and Bellingham, P},
title = {Seismic velocity structure of two types of seaward-dipping reflectors on the South American continental margin},
year = {2019}
}
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RIS format (EndNote, RefMan)

TY  - CPAPER
AB  - © 81st EAGE Conference and Exhibition 2019. All rights reserved. Seaward dipping reflectors (SDRs) are a key feature within the continent-to-ocean transition zone of volcanic passive margins. They are formed by volcanic activity during continental breakup. Along the volcanic margins of South America, we have mapped and documented two distinct types of SDR: Type I that are relatively straight and lie within faulted half-grabens that are partially overlain by Type II that are more curved and have unfaulted basal contacts. Here we conduct an automated, pre-stack, depth-migration imaging analysis on commercial seismic data to determine more about their physical properties. We find that the two SDR classes have distinct seismic velocity characteristics. While both types show a general increase in velocity with depth consistent with expected compaction and alteration/metamorphic trends, the Type I SDRs also have high velocity zones at their down-dip ends. We attribute these elevated velocities to the presence of less porous and/or more mafic rocks. We interpret them as the remnants of volcanic feeder systems along the large landward-dipping faults that bound these SDRs. Our observations imply that the SDRs document a major change in rift architecture, with magmatism linked with early tectonic stretching of the upper brittle crust transitioning into dike-fed eruptions similar to seafloor spreading.
AU  - Lonergan,L
AU  - Collier,J
AU  - McDermott,C
AU  - Fruehen,J
AU  - Bellingham,P
PY  - 2019///
TI  - Seismic velocity structure of two types of seaward-dipping reflectors on the South American continental margin
ER  -
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