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| Titel |
Seismic reflection images of lithospheric deformation in the Wharton Basin |
| VerfasserIn |
Yanfang Qin, Satish C. Singh, James Martin |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250087488
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| Publikation (Nr.) |
 EGU/EGU2014-1539.pdf |
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| Zusammenfassung |
| The Central Indian Ocean basin is deforming actively: west of Ninety-east Ridge (NER), the
deformation is taken as N-S compression whereas east of NER in the Wharton Basin, the
deformation is taken along re-activated N-S fracture zones as left-lateral strike-slip motion.
This was recently confirmed by a series of strike-slip earthquakes in 2012, including one of
the largest strike-slip earthquake on the earth of Mw=8.6 earthquake on April 11, 2012. All
these earthquakes seem to have ruptured down to 40-50 km but we do not have any direct
evidence of these ruptures. Here, we present deep seismic image from the Wharton
Basin that provide image down to 45 km depth. In order to obtain seismic image
at great depths, we use a 12 km long streamer and a low frequency enhancement
technique. The low frequency image reveals many bright dipping reflectors in the
top 10 km of the upper mantle, and the number of reflectors decreases with depth,
with one continuous reflector is imaged down to 45 km depth. Given that these
reflectors lie in the deformation zone with great earthquakes, we suggest that these
reflectors correspond to deep penetrating faults. The apparent dip of the deepest
reflector decreases with depth from ~40 to 12°, which when projected along the N-S
fracture zones becomes ~50 to 20°. We find that amplitude of this deep penetrating
reflector decreases linearly with depth down to 25 km depth (10 km below the Moho)
and then remains constant down to 45 km depth. The number of faults imaged
along a 230 km long profile and the number of earthquakes as a function of depth
show similar patterns. As well as the statistical analysis of number of earthquakes
as a function of depth/temperature for oceanic lithosphere of 50-60 Ma. These
observations indicate that the 25 km depth, which corresponds to 400° C for a
lithosphere of 55-56 Ma of age, might be the lower boundary of the intense deformation
and surpentinization. This depth also has a good agreement with the separation of
double Benioff zones. Below this depth, the deformation might be associated a great
earthquakes of the type Mw=8.6 and the reflectors might result from shear zones. |
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