Surface Rupture and Geotechnical Features of The July 2, 2013 Tanah Gayo Earthquake

Abstract

-An assessment of surface rupture and collateral ground failures can help to evaluate the impact of future earthquakes. This paper presents the results of a field survey conducted to map the surface rupture and geotechnical phenomena associated with the ground shaking during the July 2, 2013 earthquakes in Tanah Gayo Highland. The objectives of this survey are to document and to characterize the surface ruptures as well as to identify types of earthquake-induced ground failures. Results of the survey identified four best sites of possible surface rupture. Two locations are obvious surface ruptures that can be traced on primary topographic feature of the active fault segment from the north to the south, crossing Pantan Terong Hill. The fault segment has a total mapped length of 19 km, with WNW trending zone and a dextral rupture offset. The ground shaking also resulted in landslides and liquefaction in areas underlain by very fine-grained tuffaceous sands. Based on the field survey, it can be concluded that the newly defined active fault segment, the Pantan Terong segment, is likely the segment that ruptured at the July 2, 2013 Tanah Gayo earthquake. Due to the soil types and unstable rocky slopes in the hilly Central Aceh region, large-scale landslides are primary risks during an earthquake event in this region.

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

“…In addition, our preferred 12 km to the southeast (blue star) (Pesicek et al, 2010). Between these two events, most seismicity (blue circles and focal mechanisms) was associated with the Sumatran fault segments (drawn as multicolor lines), including the January 2013 M w 6.1 earthquake in Aceh segment (Ito et al, 2016) and the July 2013 M w 6.1 Tanah Gayo earthquake~30 km from the nearest segment of the Sumatran fault (Daryono & Tohari 2016;Gunawan et al, 2018). Historical events are from Pesicek et al (2010) and Nugraha et al (2018).…”

“…Earthquakes produced by rupture of faults outside the SFZ pose an additional hazard, with recent examples being the July 2013 M w 6.1 Tanah Gayo earthquake (Daryono & Tohari 2016) and the 2016 M w 6.6 Pidie Jaya Figure 1. (a) We study three M w~6 strike-slip earthquakes (blue dots with plus symbols inside) that ruptured the SFZ (drawn as multicolor lines based on Sieh & Natawidjaja, 2000) and one (blue dot with a cross symbol inside) that ruptured a blind fault near the northern coastal region of Aceh.…”

“…The Tanah Gayo event ruptured a previously unidentified active fault in Aceh,~30 km away from the nearest SFZ segment. This event triggered landslides and liquefaction and killed six people (Daryono & Tohari 2016). Three years later, the Pidie Jaya event ruptured another previously unmapped active fault near the coast of northern Aceh,~50 km away from the nearest SFZ segment (Muzli et al, 2018).…”

“…To better assess seismic hazard potential of earthquakes in mainland Sumatra, published studies have focused on paleoearthquakes (Bellier et al, 1997), epicenter relocations (Hurukawa et al, 2014;Newcomb & McCann, 1987;Nugraha et al, 2018;Pesicek et al, 2010), aftershock distributions (Muzli et al, 2018;Widiwijayanti et al, 1996), field observations of surface ruptures (Daryono et al, 2012;Daryono & Tohari, 2016;Untung et al, 1985), deterministic and probabilistic hazard assessments (Natawidjaja & Triyoso, 2007), active fault mapping (Fernandez-Blanco et al, 2016;Muksin et al, 2019;Natawidjaja et al, 2017;Sieh & Natawidjaja, 2000;Weller et al, 2012), fault slip rates (Bellier & Sebrier, 1995;Bradley et al, 2017;Genrich et al, 2000;Ito et al, 2012;Natawidjaja et al, 2017;Prawirodirdjo et al, 2000;Tong et al, 2018), in situ stress analysis (Sahara et al, 2018), source characteristics of ruptures (Duquesnoy et al, 1996;Gunawan et al, 2018;Ito et al, 2016;Prawirodirdjo et al, 2000;Reid, 1913), and postseisimic processes (Gunawan et al, 2019). However, none of these studies used well-constrained near-field geodetic data to address the seismogenic depth and spatial distribution of coseismic slip, or to study the nature of the tectonic features that control earthquake rupture sizes along the SFZ.…”

Shallow crustal earthquake models, damage, and loss predictions in Banda Aceh, Indonesia

“…The earthquake source belonged to another segment of faults that had not been recognized in the earthquake map previously. Using macro seismic surveys and surface ruptures, Rusydy et al (2015) and Daryono and Tohari (2016) found the segment is part of a previously unknown fault that crosses Takengon City striking to the north-west. Based on their findings, this study used the rupture zone as the source of the Tanoh Gayo earthquake as shown in Fig.…”