A sequence of earthquakes occurred on Alor Island, Nusa Tenggara Timur, Indonesia, beginning in November 2015 with the mainshock (⁠Mw 6.2) on 4 November 2015. We calculate the centroid moment tensor (CMT) solutions for nine of the earthquakes with Mw≥3.9⁠, which occurred between November 2015 and March 2016 using records from a temporary array of 30 broadband instruments in eastern Indonesia and Timor Leste (YS network). Our CMT results reveal an interesting pattern of ruptures in this order: (a) three foreshocks of Mw 4–5.3 all with strike‐slip mechanisms that occurred with a centroid depth of ∼13 km in the three days prior to the mainshock, (b) the mainshock on 4 November 2015, with Mw 6.2 that occurred with a deeper centroid (∼25 km) and a strike‐slip mechanism similar to the foreshocks, (c) followed by five aftershocks with Mw>3.9 at depth ∼3–15km. We further determine the fault plane and rupture direction of the mainshock and the largest foreshock (⁠Mw 5.3) by relocating the hypocenter and examining its geometrical location with respect to the centroid. We find that the fault plane strikes 97°±9° from north and that the fault ruptures westward. We propose that the rupture of this sequence of events initiated at depth ∼10 km, propagating westward and triggering the mainshock to rupture at a deeper depth (within lower crust) on a similar faulting system. The aftershocks migrate back to shallower depths and occur mainly at depth <10 km.

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.