Tectonic Fabric in the Banda Arc‐Australian Continent Collisional Zone Imaged by Teleseismic Receiver Functions

Abstract

The Banda Arc-Australian continent collision in eastern Indonesia and Timor-Leste is exemplary of an incipient oblique arc-continent collision. From west to east, the incoming Indo-Australian plate structure transitions from Cretaceous to Jurassic age oceanic lithosphere (Müller et al., 2008) to continental margin lithosphere that is inherently heterogeneous (Harris, 2011;Keep & Haig, 2010;Spakman & Hall, 2010). To the north of the plate boundary, the transition in the incoming plate structure is evident in the linear single volcanic Sunda Arc bifurcating into a double chain of islands (Figure 1a). The northern chain of islands is referred to as the inner arc, composed of volcanic rocks of Neogene age. The southern chain of islands is the non-volcanic outer arc, formed by orogenic structures. The outer arc includes the NNE-SSW oriented islands of Timor, Savu, and Rote and the NNW-SSW striking Sumba Island between the Java Trench-Timor Trough system and the volcanic arc (Figure 1).

Layered Mantle Flow Field Associated With Plate Kinematics and Slab Modulation Underneath the Horseshoe‐Shaped Banda Arc‐Islands

“…At Station SOEI, the two local splitting measurements (49°, 0.4 s and 16°, 0.25 s) from events originating in the shallow slab are comparable to the anisotropy measurements from receiver function analysis (P. Zhang et al., 2022). The measurement of (49°, 0.4 s) which is orogen‐parallel and has a larger splitting time, could be attributed to the LPO of anisotropic minerals in the lithosphere in response to the convergence (P. Zhang et al., 2022) or associated with fossil fabric formed during seafloor spreading.…”

“…At Station SOEI, the two local splitting measurements (49°, 0.4 s and 16°, 0.25 s) from events originating in the shallow slab are comparable to the anisotropy measurements from receiver function analysis (P. Zhang et al., 2022). The measurement of (49°, 0.4 s) which is orogen‐parallel and has a larger splitting time, could be attributed to the LPO of anisotropic minerals in the lithosphere in response to the convergence (P. Zhang et al., 2022) or associated with fossil fabric formed during seafloor spreading. The other measurement which has a fast orientation in accordance with the convergence direction and a smaller splitting time can be caused by aligned fluid‐saturated cracks (Crampin, 1981) deformed by NNE‐SSW or NE‐SW trending strike‐slip faults (Duffy et al., 2013) in the upper crust.…”

Impact of Ancient Tectonics on Intracontinental Deformation Partitioning: Insights From Crustal Structures of the East Junggar‐Altai Area

“…This suggests that the lower crustal layer exhibits a higher Vp/Vs ratio, which implies the presence of mafic restite generated during a magma underplating process is a more plausible explanation (Figure 8). Additionally, during magma underplating processes, the alignment of minerals like amphibolite can induce moderate to strong (3%–9%) anisotropy (Frothingham et al., 2023), which has been observed at various volcanic regions (Schulte‐Pelkum et al., 2020; P. Zhang et al., 2022). To further investigate the anisotropic properties of the lower crustal layer, we conducted an analysis by calculating an azimuthal contrast stack by computing the difference between southern and northern azimuth arrivals to highlight its anisotropic characteristic (Figure S9 in Supporting Information S1).…”