another earthquake in the east Java / Timor region of Indonesia

We had another earthquake in this region today. This is an interesting area of the world since this is a place where there is a transition between subduction to the west and collision to the east. The Island of Timor is interpreted to be part of Australia and has continental rocks that are found in Australia. While there is a large compressional plate boundary fault south of Timor, Timor was actually more part of Australia than it is part of the volcanic arc of Indonesia to the west (e.g. Java, Bali, etc.). Here is my post about the Mw 7.0 earthquake from a couple of days ago.
Here is a map showing the M = 5.0 earthquake as it relates to the Mw = 7.0 earthquake from a couple days ago. In the map, there is a large thrust fault that strikes east-west, north of the archipelago in this region. This is a back thrust (the Wetar Backthrust) as interpreted by Audley (2011) below.

Hall et al. (2012) provides a tectonic reconstruction for our enjoyment. Note how the Island of Timor is part of Australia back to 150 Ma.

Snyder et al. (1996) uses gravity data to interpret the plate boundary fault in this region.

Here is Snyder et als. (1996) interpretation of the structure of the plate boundary in this region.

Finally, here is the Audley (2011) cross section showing how the backthrust relates to the subduction zone beneath Timor.

This shows the Audley (1986) interpretation of the faulting in this region. One may see that the ISland of Timor is being popped up like an onion skin (compare with the cross section above^^^).

Here is a paper by my colleague Beau Whitney regarding the tectonics immediately to the south of Timor (Hengesh and Whitney, 2014). Here is their map showing the region of their work:


  • Audley-Charles, M.G., 1986. Rates of Neogene and Quaternary tectonic movements in the Southern Banda Arc based on micropalaeontology in: Journal of fhe Geological Society, London, Vol. 143, 1986, pp. 161-175.
  • Audley-Charles, M.G., 2011. Tectonic post-collision processes in Timor, Hall, R., Cottam, M. A. &Wilson, M. E. J. (eds) The SE Asian Gateway: History and Tectonics of the Australia–Asia Collision. Geological Society, London, Special Publications, 355, 241–266.
  • Hall, R., Audley-Charles, M.G., Banner, F.T., Hidayat, S., and Tobing, S.L., 1988. Basement rocks of the Halmahera region, eastern Indonesia: a Late Cretaceous-early Tertiary arc and fore-arc in: Journal of the Geological Society, London, Vol. 145, 1988, pp. 65-84.
  • Hangesh, J. and Whitney, B., 2014. Quaternary Reactivation of Australia’s Western Passive Margin: Inception of a New Plate Boundary? in: 5th International INQUA Meeting on Paleoseismology, Active Tectonics and Archeoseismology (PATA), 21-27 September 2014, Busan, Korea, 4 pp.
  • Snyder, D.B., Milsom, J., and Prasetyo, H., 1996. Geophysical evidence for local indentor tectonics in the Banda arc east of Timor in Hall, R. & Blundell, D. (eds), 1996, Tectonic Evolution of Southeast Asia, Geological Society Special Publication No. 106, pp. 61-73.

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