Abstract
We analyzed receiver function of teleseismic events recorded at twelve Indonesian-GEOFON (IA-GE) broadband stations using nonlinear Neighbourhood Algorithm (NA) inversion and H-k stacking methods to estimate crustal thickness, Vp/Vs ratios and S-wave velocity structure along Sunda-Banda arc transition zone. We observed crustal thickness of 34–37 km in Timor Island, which is consistent with the previous works. The thick crust (> 30 km) is also found beneath Sumba and Flores Islands, which might be related to the arc-continent collision causing the thickened crust. In Timor and Sumba Islands, we observed high Vp/Vs ratio (> 1.84) with low velocity zone that might be associated with the presence of mafic and ultramafic materials and fluid filled fracture zone. The high Vp/Vs ratio observed at Sumbawa and Flores volcanic Islands might be an indication of partial melt related to the upwelling of hot asthenosphere material through the subducted slab.
Highlights
The Sunda-Banda Arc transition zone has been known as one of the most complicated tectonic setting in the world providing one the best modern examples of the early stages of transition from subduction to arc-continent collision (Fig. 1)
Gravity modelling has been conducted in Timor Island indicating that the Moho depth in this island ranges from 30 to 40 km (Milsom and Audley-Charles 1986, Bowin et al.1980, Kaye 1989). he marine seismic reflection study conducted by Shulgin et al (2009) in the east of Sumba reveals 12-15 thick crust representing the continental character of the Australian lithosphere continuous through the outer Banda arc
The combined analysis of seismic wideǦangle refraction, multichannel streamer and gravity data has been conducted in south of Lombok, suggesting the significant changes in the incoming crustal structure which ranges from 7 km thick of oceanic crust offshore Lombok (Planert et al 2010) to 12 km thick crystalline crust of the Australian continental margin (Shulgin et al 2009)
Summary
The Sunda-Banda Arc transition zone has been known as one of the most complicated tectonic setting in the world providing one the best modern examples of the early stages of transition from subduction to arc-continent collision (Fig. 1). It developed as a consequence of the interaction between the Australian lithosphere and the Banda Arc in the Pliocene (Hall and Smyth 2008). The structural evolution of this area is characterized by different tectonic episodes including rifting of Timor, Savu Basin and Sumba evolution This complicated tectonic setting causes this area to be an ideal place to study the lithologic changes in crustal structures associated with the deformation along the plate boundary. The combined analysis of seismic wideǦangle refraction, multichannel streamer and gravity data has been conducted in south of Lombok, suggesting the significant changes in the incoming crustal structure which ranges from 7 km thick of oceanic crust offshore Lombok (Planert et al 2010) to 12 km thick crystalline crust of the Australian continental margin (Shulgin et al 2009)
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