Earthquake supercycles on the Mentawai segment of the Sunda megathrust in the seventeenth century and earlier

Abstract

Over at least the past millennium, the Mentawai segment of the Sunda megathrust has failed in sequences of closely timed events rather than in single end‐to‐end ruptures—each the culmination of an earthquake “supercycle.” Here we synthesize the sixteenth‐ and seventeenth‐century coral microatoll records into a chronology of interseismic and coseismic vertical deformation. We identify at least five discrete uplift events in about 1597, 1613, 1631, 1658, and 1703 that likely correspond to large megathrust ruptures. This sequence contrasts with the following supercycle culmination, which involved only two large ruptures in 1797 and 1833. Fault slip modeling suggests that together the five cascading ruptures involved failure of the entire Mentawai segment. Interseismic deformation rates also changed after the onset of the rupture sequence, as they did after the 1797 earthquake. We model this change as an altered distribution of fault coupling, presumably triggered by the ~1597 rupture. We also analyze the far less continuous microatoll record between A.D. 1 and 1500. While we cannot confidently delineate the extent of any megathrust rupture during that period, all evidence suggests that individual major ruptures involve only part of the Mentawai segment, often overlap below the central Mentawai Islands, often trigger coupling changes, and occur in clusters that cumulatively cover the entire Mentawai segment at the culmination of each supercycle. It is clear that each Mentawai rupture sequence evolves uniquely in terms of the order and grouping of asperities that rupture, suggesting heterogeneities in fault frictional properties at the ~100 km scale.

Kinetic Models for Healing of the Subduction Interface Based on Observations of Ancient Accretionary Complexes

“…However, the greatest subduction zone earthquakes are correlated with smooth subducting interfaces and thick subducting sediment piles (Lallemand et al, 2018;van Rijsingen et al, 2019;Scholl et al, 2015). Moreover, in records of repeated earthquake cycles from microatoll records from Sumatra, the arrangement of asperities can change from event to event (Philibosian et al, 2017).…”

Stratigraphic Control of Frontal Décollement Level and Structural Vergence and Implications for Tsunamigenic Earthquake Hazard in Sumatra, Indonesia

“…In the vicinity of the study area, frictional locking of the Sunda megathrust extends to a depth of ~40 km and ruptures of the deep locked patch are common (Chlieh et al, ; Lange et al, ; Prawirodirdjo et al, ). Paleogeodetic, historical, and instrumental records of earthquakes reveal that in this region the megathrust tends to rupture in supercycles of slip events rather than during single throughgoing ruptures like the 2004 Sumatra‐Andaman earthquake (Natawidjaja et al, ; Philibosian et al, ; Philibosian et al, ; Sieh et al, ). A sequence of two large megathrust earthquakes in 2007 resulted from complex ruptures of the frictionally locked plate interface but did not propagate to shallow levels and did not generate significant tsunami waves (Konca et al, ).…”

“…Increased stress on the updip area of the megathrust following these events may have caused the 2010 Mentawai earthquake (Hill et al, ). Few of these large earthquakes have geological or historical evidence for large tsunamis, and the paleogeodetic data do not constrain whether slip propagated to the surface during individual events (Philibosian et al, ). If propagation of rupture to shallow levels during great earthquakes that rupture the deep locked patch is uncommon in this area, shallower tsunamigenic ruptures may be more common here.…”

Piecemeal Rupture of the Mentawai Patch, Sumatra: The 2008 Mw 7.2 North Pagai Earthquake Sequence

“…This sequence of earthquakes ruptured a small area in the middle of the Mentawai patch (Figure ) and has not been extensively studied to date. The fact that only a small area of the Mentawai patch has ruptured so far could have important implications for understanding the unbroken megathrust in the northern half of the Mentawai patch, particularly given recent results from coral paleogeodetic data that suggest that segmented ruptures of the patch have happened in past supercycles (Philibosian et al, ). That is, the likelihood of a single great earthquake in the near future remains high as previously suggested (Chlieh et al, ; Sieh et al, ), but the possibility of releasing the cumulative strain in piecemeal cannot be ruled out.…”