ORCID Profile
0000-0001-6858-2447
Current Organisation
University of Aberdeen
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Publisher: American Geophysical Union (AGU)
Date: 11-2022
DOI: 10.1029/2022GC010564
Abstract: The relative paucity of recent post‐ subduction environments globally has meant that, so far, little is known about tectonic processes that occur during and after subduction termination, as previously convergent tectonic plates adjust to the new stress regime. The region of Southeast Asia that now encompasses northern Borneo has been host to two sequential episodes of subduction—both now terminated—since the mid‐Paleogene. It is expected that these processes will have left signatures in the fabric of the upper mantle, which are manifest in the form of seismic anisotropy. We investigate the evidence for, and alignment of, anisotropic fabrics by measuring the splitting of a family of teleseismic shear phases. These observations provide a measure of the orientation of the effective anisotropic elastic tensor, in the form of the orientation of the fast shear‐wave polarization, ϕ, and add constraints on the strength of the anisotropic fabric, in the form of the delay time, δt . We observe two principal trends across northern Borneo that appear to be confined to the lithosphere. These patterns are likely related to tectonic processes associated with subduction, continental collision, and oceanic basin formation, events that can exert primary influence on the formation of post‐subduction settings.
Publisher: American Geophysical Union (AGU)
Date: 04-02-2022
DOI: 10.1029/2021GL096117
Abstract: We use two‐plane‐wave tomography with a dense network of seismic stations across Sabah, northern Borneo, to image the shear wave velocity structure of the crust and upper mantle. Our model is used to estimate crustal thickness and the depth of the lithosphere‐asthenosphere boundary (LAB) beneath the region. Calculated crustal thickness ranges between 25 and 55 km and suggests extension in a NW‐SE direction, presumably due to back‐arc processes associated with subduction of the Celebes Sea. We estimate the β‐factor to be 1.3–2, well below the initiation of seafloor spreading. The LAB is, on average, at a depth of 100 km, which is inconsistent with models that ascribe Neogene uplift to wholescale removal of the mantle lithosphere. Instead, beneath a region of Plio‐Pleistocene volcanism in the southeast, we image a region 50–100 km across where the lithosphere has thinned to km, supporting recent suggestions of lower lithospheric removal through a Rayleigh‐Taylor instability.
Publisher: American Geophysical Union (AGU)
Date: 11-10-2022
DOI: 10.1029/2022GL099123
Abstract: Subduction polarity reversal (SPR) is a key subduction initiation mechanism often associated with arc‐continent collision zones. Northern Borneo has long been recognized as a location where sequential but opposing subduction zones were present in the Miocene, but has not been examined in the context of SPR. Here, we exploit teleseismic data from northern Borneo to investigate crustal thickness variations using Virtual Deep Seismic Sounding (VDSS). Our results reveal a thick crustal root beneath the Crocker Range and an area of relatively thin crust in the southeast, which appears to extend northeast into the Sulu Sea, where back‐arc rifting behind the younger subduction zone developed. Overall, our findings are consistent with predictions from numerical models of SPR involving arc‐continent collision, but with several important differences—including a substantial mountain range and more limited back‐arc rifting that can be attributed to northern Borneo being an ex le of SPR involving continent‐continent collision.
Publisher: American Geophysical Union (AGU)
Date: 07-2018
DOI: 10.1029/2018JB015473
Publisher: Springer Science and Business Media LLC
Date: 19-06-2023
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Amy Gilligan.