The Java convergent margin: structure, seismogenesis and subduction processes
Heidrun Kopp, 2011. "The Java convergent margin: structure, seismogenesis and subduction processes", The SE Asian Gateway: History and Tectonics of the Australia-Asia Collision, R. Hall, M. A. Cottam, M. E. J. Wilson
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The Java margin is characterized by a distinct variation in lower to upper plate material transfer and recurring catastrophic tsunamogenic earthquakes. Both processes are closely linked to the subduction of oceanic basement relief resulting in varying degrees of fore-arc deformation. Tomographic models of refraction seismic profiles and reflection seismic lines in combination with high-resolution multibeam bathymetric data reveal the variability in the deep structure and deformation of the Java fore-arc. Shallow subduction processes are governed by the sediment supply in the trench as well as by the nature and fabric of the oceanic lithosphere. The deep structure of the fore-arc reveals a shallow upper plate crust–mantle transition, present along the entire Java margin section. The serpentinized fore-arc mantle wedge governs the depth extent of the seismogenic zone here, which is narrower compared to its Sumatran analogue. In addition, offshore central Java, high relief oceanic basement features potentially act as asperities as well as barriers to seismic rupture, limiting the possible magnitude of subduction thrust earthquakes. However, the potential for geohazards, in particular tsunamis, is high along the entire margin. This results from tsunamogenic earthquakes, ubiquitous splay faults and potentially tsunamogenic landslides, which further increase the risk of future tsunamis.
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Collision between Australia and SE Asia began in the Early Miocene and reduced the former wide ocean between them to a complex passage which connects the Pacific and Indian Oceans. Today, the Indonesian Throughflow passes through this gateway and plays an important role in global thermohaline flow. The surrounding region contains the maximum global diversity for many marine and terrestrial organisms. Reconstruction of this geologically complex region is essential for understanding its role in oceanic and atmospheric circulation, climate impacts, and the origin of its biodiversity.
The papers in this volume discuss the Palaeozoic to Cenozoic geological background to Australia and SE Asia collision. They provide the background for accounts of the modern Indonesian Throughflow and oceanographic changes since the Neogene, and consider aspects of the region’s climate history.