Coral evidence for earthquake recurrence and an A.D. 1390–1455 cluster at the south end of the 2004 Aceh–Andaman rupture

Abstract

Coral records of relative sea level change provide a history of vertical interseismic and coseismic deformation along the coast of northern Simeulue Island, Sumatra, and reveal details about earthquakes in the 10th and 14th–15th centuries A.D. along the southern end of the December 2004 Mw 9.2 Sunda megathrust rupture. Over a 56 year period between A.D. 1390 and 1455, northern Simeulue experienced a cluster of megathrust ruptures, associated with total uplift that was considerably more than in 2004. Uplifted corals at two sites constrain the first event of the cluster to A.D. 1393 ± 3 and 1394 ± 2 (2σ). A smaller but well‐substantiated uplift occurred in northern Simeulue in 1430 ± 3. An inferred third uplift, in A.D. 1450 ± 3, killed all corals on the reef flats of northern Simeulue. The amount of uplift during this third event, though confirmed only to have exceeded 28 and 41 cm at two sites, probably surpassed the 100 and 44 cm that occurred, respectively, at those sites in 2004, and it was likely more than in 2004 over all of northern Simeulue. The evidence for past earthquake clustering combined with the inference of considerably greater uplift in A.D. 1390–1455 than in 2004 suggests that strain may still be stored along the southernmost part of the 2004 rupture. Interseismic subsidence rates recorded by northern Simeulue coral microatolls have varied by up to a factor of 4 at some sites from one earthquake cycle to another.

A 15 year slow‐slip event on the Sunda megathrust offshore Sumatra

“…In the Sumatran subduction zone, temporal changes in long-term deformation rates have been reported to occur before or after major megathrust earthquakes [e.g., Prawirodirdjo et al, 2010;Philibosian et al, 2014;Meltzner et al, 2010Meltzner et al, , 2012. Most of these rate changes maintained a sense of displacement consistent with locking on the underlying megathrust and have been modeled as spatiotemporal variations in interseismic coupling and/or downdip limits of locking.…”

“…The coral microatolls were slabbed, X-rayed, and analyzed following the methods described by Meltzner et al, [2010Meltzner et al, [ , 2012 and Meltzner and Woodroffe [2015]. The interpreted coral cross sections and corresponding time series for the relevant corals are presented in Figures S1-S6 and Table S1 in the supporting information.…”

“…Microatolls are coral colonies that grow upward to a limit near mean low water springs, and their upper surfaces can track changes in relative sea level (RSL) over time [Scoffin et al, 1978;Taylor et al, 1987;Zachariasen et al, 2000;Meltzner et al, 2010]. Microatoll morphologies form because prolonged subaerial exposure at times of extreme low water limits the highest level to which the coral colonies can grow [Briggs et al, 2006;Meltzner et al, 2010;Meltzner and Woodroffe, 2015]. Flat-topped microatolls record RSL stability; colonies that rise radially outward toward their perimeter reflect rising RSL during their decades of growth, and colonies with progressively lower diedowns as they grow outward reflect gradually falling RSL.…”

“…For example, coral microatolls along the Sumatran subduction zone provide high-resolution records of vertical deformation over the past several centuries [e.g., Zachariasen et al, 2000;Meltzner et al, 2010;Philibosian et al, 2014]. Using these data, reconstructed interseismic uplift and subsidence at multiple sites over the past three centuries.…”

Evolution of anthropogenic Pb and Pb isotopes in the deep North Atlantic Ocean and the Indian Ocean

“…The first coral core (core GIM) was collected in February 1996 in the lagoon of After cutting the coral into slabs, the annual bands of the coral were X-rayed and the chronologies were determined by analyzing 23 0 Th in critical points (Meltzner et al, 2010) and counting bands between those critical points. The coral used for this research (LKP- The top layer of the core (from 2010) was not analyzed due to potential contamination from organic tissues.…”