Late Quaternary eruption of the Ranau Caldera and new geological slip rates of the Sumatran Fault Zone in Southern Sumatra, Indonesia

Abstract

Over the last decade, studies of natural hazards in Sumatra have focused primarily on great earthquakes and associated tsunamis produced by rupture of the Sunda megathrust. However, the Sumatran Fault and the active volcanic arc present proximal hazards to populations on mainland Sumatra. At present, there is little reliable information on the maximum magnitudes and recurrence intervals of Sumatran Fault earthquakes, or the frequency of paroxysmal caldera-forming (VEI 7-8) eruptions. Here, we present new radiocarbon dates of paleosols buried under the voluminous Ranau Tuff that constrain the large caldera-forming eruption to around 33,830-33,450 calender year BP (95% probability). We use the lateral displacement of river channels incised into the Ranau Tuff to constrain the long-term slip rate of two segments of the Sumatran Fault. South of Ranau Lake, the Kumering segment preserves isochronous right-lateral channel offsets of approximately 350 ± 50 m, yielding a minimum slip rate of 10.4 ± 1.5 mm/year for the primary active fault trace. South of Suoh pull-apart depression, the West Semangko segment offsets the Semangko River by 230 ± 60 m, yielding an inferred slip rate of 6.8 ± 1.8 mm/year. Compared with previous studies, these results indicate more recent high-volume volcanism in South Sumatra and increased seismic potency of the southernmost segments of the Sumatran Fault Zone.

Updating active fault maps and sliprates along the Sumatran Fault Zone, Indonesia

“…In other word, slip rates at Sianok valley increase a bit higher, and slip rates near Toba become only half as much as those of the previous study. In south Sumatra, a new measurement on geological slip rates of the Kumering segment in the south of Lake Ranau has been conducted [23]. Their analysis yields about 8 to 12 mm/year, which is twice as much than the previous measurement [2].…”

“…Hence, based on their K-Ar dating of plagioclase of the Ranau Tuff that yielded an average age of 0.55 ± 0.15 Ma, and assuming those geomorphic features were formed right after the paroxysmal eruption of Ranau Tuff blanketed the old topography, they estimated a slip rate of 5.5 ± 1.9 mm/yr for the Kumering Fault (or they called it as the Ranau-Suoh fault). However, this measurement has fatal mistakes on both the dating and their interpreted offset [23].…”

Timing, magnitude and geochemistry of major Southeast Asian volcanic eruptions: identifying tephrochronologic markers

“…). The Sumatran arc segment hosts: (1) Toba caldera in the north, which produced the 1.2 ± 0.16 Ma Haranggoal dacite tuff (HDT; Nishimura et al ., ; Chesner et al ., ), the 792.4 ± 0.5 ka old Toba tuff (OTT), the 502 ± 0.7 ka middle Toba tuff (MTT), and the 73.7 ± 0.3 ka YTT (Mark et al ., ); (2) Maninjau caldera in West Sumatra, which formed at 52 ± 3 ka (Alloway et al ., ); (3) Masurai caldera in Jambi, which formed at 32.768 14 C ka bp (Rohiman et al ., ); (4) Ranau caldera in the south, which formed at 33.64 ± 0.19 cal ka bp (Natawidjaja et al ., ); and (5) Krakatau caldera in the straits between Sumatra and Java, which is the source of the famous 1883 ad caldera‐forming eruption (Self, ). The Banda arc segment hosts: (1) Batur caldera on the island of Bali, which produced the 29.3 14 C ka bp (34.56 ± 3.68 cal ka bp ; VOGRIPA) Ubud ignimbrite and the 20.15 ± 0.71 14 C ka bp (24.38 ± 3.07 cal ka bp ; VOGRIPA) Gunungkawi ignimbrite (Reubi and Nicholls, ; Sutawidjaja, ); (2) Samalas caldera on Lombok island, which formed in 1257 ad on the flank of Rinjani volcano (Lavigne et al ., ); and (3) Tambora caldera on West Nusa Tenggara island, which is the source of the famous 1815 ad eruption followed by the year without a summer (Oppenheimer, ).…”

“…‘BAnd’ stands for Basaltic‐Andesite. Data from [2] (Mandeville et al ., ), [3] (Foden, ), [4] (Reubi and Nicholls, ), [5] (Vidal et al ., ), [6] (Alloway et al ., ), [7] (Natawidjaja et al ., ), [8] (Alloway et al ., ), [9] (Chesner, ), [10] (Chesner and Luhr, ), [14] (Devine et al ., ), [15] (Gertisser et al ., ), [17] (Camus et al ., ), [18] (Smith et al ., ), [19] (Vidal et al ., ), [20] (Pallister et al ., ), [21] (Rutherford and Devine, ), [22] (Luhr and Melson, ), [25] (Fournelle et al ., ), [27] (Hammer et al ., ), [29] (Ku et al ., ), [31] (Mirabueno et al ., ). [Color figure can be viewed at wileyonlinelibrary.com]…”

Weak Tectono-Magmatic Relationships along an Obliquely Convergent Plate Boundary: Sumatra, Indonesia

“…Jaxybulatov et al, 2014). Other volcanic areas host calderas (as Ranau caldera; Bellier and Sébrier, 1994;Natawidjaja et al, 2017), stratovolcanoes (between 600 and 3800 m high), domes and geothermal activity (Gasparon, 2005). The latter includes the Sarulla graben (Hickman et al, 2004) and the Tarutung and Silangkitang geothermal areas, where the fluid pathways are related to pull-aparts (Muksin et al, 2013(Muksin et al, , 2014, negative flowers (Nukman and Moeck, 2013) and subvertical (Moore et al, 2001) splays of the GSF.…”