Continued Earthquake Hazard in Northern Sumatra

Abstract

The occurrence of two large earthquakes (M w = 8.4 and M w = 7.9) along the Sumatran west coast on 12 September 2007 as well as an M w = 7.4 event on 20 February 2008 have again put the high earthquake hazard of this region into focus. These events are the most recent in a series of major subduction zone earthquakes that began with the great

Structural Controls on Rupture Extent of Recent Sumatran Fault Zone Earthquakes, Indonesia

“…Concerns about the potential seismic hazard of the SFZ have escalated after a series of M w > 8 earthquakes (the 26 December 2004 M w 9.2 Sumatra-Andaman event, the 28 March 2005 M w 8.6 Nias-Simeulue event, and the 12 September 2007 M w 8.4 Bengkulu event) were generated by the Sunda megathrust offshore Sumatra, starting in 2004. These large megathrust events increased stress loading on the SFZ (Cattin et al, 2009;Nalbant et al, 2005;Sørensen & Atakan, 2008) and likely triggered more frequent moderate seismicity along the SFZ, including five 6 ≤ M < 7 earthquakes: the 2007 M w 6.4 and 6.3 earthquakes (Daryono et al, 2012;Nakano et al, 2010) that caused 69 fatalities and more than 100 injuries (hereafter referred to as the 2007 Lake Singkarak doublet); the 2008 M w 6.0 Toru earthquake that broke the Toru segment (Hurukawa et al, 2014); the 2009 M w 6.6 earthquake that broke the Dikit seismic gap (Hurukawa et al, 2014) (hereafter referred to as the 2009 Dikit event); and the January 2013 M w 6.1 earthquake that ruptured the Aceh creeping segment (Ito et al, 2016) (Figure 1). The 2008 Toru, the 2009 Dikit, and the January 2013 Aceh events did not cause casualties.…”

“…(b) Block modeling result based on an updated decadal GPS velocity field, suggesting a nearly constant slip rate along the SFZ of~15 mm/year (Bradley et al, 2017). (c) The occurrence of large earthquakes on the Sunda megathrust (red stars with dashed lines showing the estimated length of the earthquake ruptures) has increased stress loading on the SFZ (Cattin et al, 2009;Nalbant et al, 2005;Sørensen & Atakan, 2008) and hence triggered more seismic activity along the SFZ. Vertical axis reflects distance along the SFZ from the equator.…”

The Tectonic Framework of the Sumatran Subduction Zone

“…The Sumatran fault, with its rich history of damaging earthquakes, is a source of considerable hazard to communities (Sorensen 2008). The mountains of Sumatra form a long linear chain within which sit many fertile, highly populated valleys.…”

Segmentation of the Sumatran fault

“…The fault has produced several large historical earthquakes, e.g., 1895 ~ M w 7.6, 1945 ~ M w 7.7, and in recent history Sungaipenuh, Jambi Province, 2009 M w 6.6. Gaps in seismic activity have been remarked along the fault, and Sorensen [] suggests that the Sumatra‐Andaman 2004 M w 9.1 earthquake, to the north of the GSF, marked the start of a 200 year seismic cycle. As Parsons et al [] succinctly point out, there is a “persistent and difficult issue in seismology” when matching the long‐term recurrence rates of largest earthquakes with instrumental recordings of smaller earthquakes.…”