Receiver function study in northern Sumatra and the Malaysian peninsula |
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| Authors: | Katrin Kieling Dirk Roessler Frank Krueger |
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| Institution: | 1.Institute of Geosciences,University of Potsdam,Potsdam,Germany |
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| Abstract: | In this receiver function study, we investigate the structure of the crust beneath six seismic broadband stations close to
the Sunda Arc formed by subduction of the Indo-Australian under the Sunda plate. We apply three different methods to analyse
receiver functions at single stations. A recently developed algorithm determines absolute shear-wave velocities from observed
frequency-dependent apparent incidence angles of P waves. Using waveform inversion of receiver functions and a modified Zhu
and Kanamori algorithm, properties of discontinuities such as depth, velocity contrast, and sharpness are determined. The
combination of the methods leads to robust results. The approach is validated by synthetic tests. Stations located on Malaysia
show high-shear-wave velocities (V
S) near the surface in the range of 3.4–3.6 km s − 1 attributed to crystalline rocks and 3.6–4.0 km s − 1 in the lower crust. Upper and lower crust are clearly separated, the Moho is found at normal depths of 30–34 km where it
forms a sharp discontinuity at station KUM or a gradient at stations IPM and KOM. For stations close to the subduction zone
(BSI, GSI and PSI) complexity within the crust is high. Near the surface low V
S of 2.6–2.9 km s − 1 indicate sediment layers. High V
S of 4.2 km s − 1 are found at depth greater than 6 and 2 km at BSI and PSI, respectively. There, the Moho is located at 37 and 40 km depth.
At station GSI, situated closest to the trench, the subducting slab is imaged as a north-east dipping structure separated
from the sediment layer by a 10 km wide gradient in V
S between 10 and 20 km depth. Within the subducting slab V
S ≈ 4.7 km s − 1. At station BSI, the subducting slab is found at depth between 90 and 110 km dipping 20° ± 8° in approximately N 60° E. A
velocity increase in similar depth is indicated at station PSI, however no evidence for a dipping layer is found. |
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