Detailed seismic velocity of the incoming subducting sediments in the 2004 great Sumatra earthquake rupture zone from full waveform inversion of long offset seismic data
Abstract The nature of incoming sediments defines the locking mechanism on the megathrust, and the development and evolution of the accretionary wedge. Here we present results from seismic full waveform inversion of 12 km long offset seismic reflection data within the trench in the 2004 Sumatra eart...
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Wiley
2017-04-01
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| Series: | Geophysical Research Letters |
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| Online Access: | https://doi.org/10.1002/2016GL072175 |
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| author | Yanfang Qin Satish C. Singh |
| author_facet | Yanfang Qin Satish C. Singh |
| author_sort | Yanfang Qin |
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| description | Abstract The nature of incoming sediments defines the locking mechanism on the megathrust, and the development and evolution of the accretionary wedge. Here we present results from seismic full waveform inversion of 12 km long offset seismic reflection data within the trench in the 2004 Sumatra earthquake rupture zone area that provide detailed quantitative information on the incoming oceanic sediments and the trench‐fill sediments. The thickness of sediments in this area is 3–4 km, and P wave velocity is as much as ~4.5 km/s just above the oceanic crust, suggesting the presence of silica‐rich highly compacted and lithified sediments leading to a strong coupling up to the subduction front. We also find an ~70–80 m thick low‐velocity layer, capped by a high‐velocity layer, at 0.8 km above the subducting plate. This low‐velocity layer, previously identified as high‐amplitude negative polarity reflection, could have porosity of up to 30% containing overpressured fluids, which could act as a protodécollement seaward from the accretionary prism and décollement beneath the forearc. This weak protodécollement combined with the high‐velocity indurated sediments above the basement possibly facilitated the rupture propagating up to the front during the 2004 earthquake and enhancing the tsunami. We also find another low‐velocity layer within the sediments that may act as a secondary décollement observed offshore central Sumatra, forming bivergent pop‐up structures and acting as a conveyer belt in preserving these pop‐up structures in the forearc region. |
| format | Article |
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| language | English |
| publishDate | 2017-04-01 |
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| spelling | doaj-art-ab1a7a9c7ac942a69b5d7a3c55ea92982025-08-20T01:51:46ZengWileyGeophysical Research Letters0094-82761944-80072017-04-014473090309910.1002/2016GL072175Detailed seismic velocity of the incoming subducting sediments in the 2004 great Sumatra earthquake rupture zone from full waveform inversion of long offset seismic dataYanfang Qin0Satish C. Singh1Equipe de Géosciences Marines Institut de Physique du Globe de Paris (CNRS, Paris Diderot, Sorbonne Paris Cité) Paris FranceEquipe de Géosciences Marines Institut de Physique du Globe de Paris (CNRS, Paris Diderot, Sorbonne Paris Cité) Paris FranceAbstract The nature of incoming sediments defines the locking mechanism on the megathrust, and the development and evolution of the accretionary wedge. Here we present results from seismic full waveform inversion of 12 km long offset seismic reflection data within the trench in the 2004 Sumatra earthquake rupture zone area that provide detailed quantitative information on the incoming oceanic sediments and the trench‐fill sediments. The thickness of sediments in this area is 3–4 km, and P wave velocity is as much as ~4.5 km/s just above the oceanic crust, suggesting the presence of silica‐rich highly compacted and lithified sediments leading to a strong coupling up to the subduction front. We also find an ~70–80 m thick low‐velocity layer, capped by a high‐velocity layer, at 0.8 km above the subducting plate. This low‐velocity layer, previously identified as high‐amplitude negative polarity reflection, could have porosity of up to 30% containing overpressured fluids, which could act as a protodécollement seaward from the accretionary prism and décollement beneath the forearc. This weak protodécollement combined with the high‐velocity indurated sediments above the basement possibly facilitated the rupture propagating up to the front during the 2004 earthquake and enhancing the tsunami. We also find another low‐velocity layer within the sediments that may act as a secondary décollement observed offshore central Sumatra, forming bivergent pop‐up structures and acting as a conveyer belt in preserving these pop‐up structures in the forearc region.https://doi.org/10.1002/2016GL072175subductionfull waveform inversionsedimentsmegathrustforearc |
| spellingShingle | Yanfang Qin Satish C. Singh Detailed seismic velocity of the incoming subducting sediments in the 2004 great Sumatra earthquake rupture zone from full waveform inversion of long offset seismic data Geophysical Research Letters subduction full waveform inversion sediments megathrust forearc |
| title | Detailed seismic velocity of the incoming subducting sediments in the 2004 great Sumatra earthquake rupture zone from full waveform inversion of long offset seismic data |
| title_full | Detailed seismic velocity of the incoming subducting sediments in the 2004 great Sumatra earthquake rupture zone from full waveform inversion of long offset seismic data |
| title_fullStr | Detailed seismic velocity of the incoming subducting sediments in the 2004 great Sumatra earthquake rupture zone from full waveform inversion of long offset seismic data |
| title_full_unstemmed | Detailed seismic velocity of the incoming subducting sediments in the 2004 great Sumatra earthquake rupture zone from full waveform inversion of long offset seismic data |
| title_short | Detailed seismic velocity of the incoming subducting sediments in the 2004 great Sumatra earthquake rupture zone from full waveform inversion of long offset seismic data |
| title_sort | detailed seismic velocity of the incoming subducting sediments in the 2004 great sumatra earthquake rupture zone from full waveform inversion of long offset seismic data |
| topic | subduction full waveform inversion sediments megathrust forearc |
| url | https://doi.org/10.1002/2016GL072175 |
| work_keys_str_mv | AT yanfangqin detailedseismicvelocityoftheincomingsubductingsedimentsinthe2004greatsumatraearthquakerupturezonefromfullwaveforminversionoflongoffsetseismicdata AT satishcsingh detailedseismicvelocityoftheincomingsubductingsedimentsinthe2004greatsumatraearthquakerupturezonefromfullwaveforminversionoflongoffsetseismicdata |