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

Abstract

The tectono-magmatic relationships along obliquely convergent plate boundaries, where strain partitioning promotes strike-slip structures along the volcanic arc, are poorly known. Here it is unclear if and, in case, how the strike-slip structures control volcanic processes, distribution and size. To better define the possible tectono-magmatic relationships along strike-slip arcs, we merge available information on the case study of Sumatra (Indonesia) with field structural data. The Sumatra arc (entire volcanic belt) consists of 48 active volcanoes. Of these, 46% lie within 10 km from the dextral Great Sumatra Fault (GSF), which carries most horizontal displacement on the overriding plate, whereas 27% lie at >20 km from the GSF. Among the volcanoes at <10 km from GSF, 48% show a possible structural relation to the GSF, whereas only 28% show a clear structural relation, lying in pull-aparts or releasing bends; these localized areas of transtension (local extensional zone) do not develop magmatic segments. There is no relation between the GSF along-strike slip rate variations and the volcanic productivity. The preferred N30 • -N40 • E volcano alignment and elongation are subparallel to the convergence vector or to the GSF. The structural field data, collected in the central and southern GSF, show, in addition to the dextral motions along NW-SE to N-S striking faults, also normal motions (extending WNW-ESE or NE-SW), suggesting local reactivations of the GSF. Overall, the collected data suggest a limited tectonic control on arc volcanism. The tectonic control is mostly expressed by the mean depth of the slab surface below the volcanoes (130 ± 20 km) and, subordinately, local extension along the GSF. The latter, when WNW-ESE oriented (more common), may be associated with the overall tectonic convergence, as suggested by the structural data; conversely, when NE-SW oriented (less common), the extension may result from co-and post-seismic arc normal extension, as supported by the 2004 mega-earthquake measurements. Overall, the strike-slip arc of Sumatra has intermediate features between those of extensional and contractional arcs.

Revisiting seismic hazard assessment for Peninsular Malaysia using deterministic and probabilistic approaches

“…This is in line with the Global Positioning System (GPS) data studied by McCaffrey et al (2000) that suggested a uniform slip rate of 21 ± 5 mm yr −1 across central Sumatra. A geomorphology study of the SFZ by Sieh and Natawidjaja (2000) and Acocella et al (2018) found it to be highly segmented with 19 major geometrically defined segments. Termed "equatorial bifurcation", the largest irregularity is located at the Equator, where the fault separates into two subparallel branches at approximately 35 km apart (Sieh and Natawidjaja, 2000).…”

“…Although numerous GMPEs have been developed and applied worldwide, not many GMPEs are available exclusively for Peninsular Malaysia due to its relatively lower local seismicity and distant location from active seismic hotspots such as the Sumatran region. Naturally, past attempts either adapted or adopted regional GMPEs or relied on the available limited data for developing GMPEs suitable for this region (Adnan et al, 2005;Pan and Megawati, 2002;Petersen et al, 2004). The collection of seismic ground motion data since 2004 by MMD, albeit relatively smaller in quantity compared to more earthquake active regions, has since allowed researchers to either identify suitable GMPEs (Van et al, 2016) or develop independent GMPEs for the peninsula (Adnan and Suhaltril, 2009;Loi, 2018;Nabilah and Balendra, 2012;Shoushtari et al, 2016) using the available ground motion records.…”

“…PGA Maps of Peninsular Malaysia at rock site condition affected by the Sumatran sources at 10 % and 2 % in 50 years probability of exceedance, respectively. PM02 denotes Pan and Megawati (2002), P04 denotes Petersen et al (2004), A05 denotes Adnan et al (2005), A06 denotes Adnan et al (2006) and DMS16 denotes the Draft National Annex by the Department of Standards Malaysia (2016).…”

Fluid Geochemistry Contribution to the Interpretation of the 2011–2012 Unrest of Santorini, Greece, in the Frame of the Dynamics of the Aegean Volcanic Arc

“…In the second case, volcanic activity may be partly controlled by the regional tectonic activity, including the seismic cycle of the subduction zone (Acocella, , and references therein). In particular, the latter feature has been object of several recent studies (Acocella et al, ; Eggert & Walter, ; Hill et al, ; Manga & Brodsky, ; Pritchard et al, ; Takada & Fukushima, ; Walter & Amelung, ). The consensus is that the activity of faults and the related seismicity along the subducting and the overriding plates may be responsible for extension in the overriding plate, from the trench to the area of the volcanic arc included.…”

Revisiting Seismic Hazard Assessment For Peninsular Malaysia Using Deterministic And Probabilistic Approaches

“…This is in line with the Global Positioning System (GPS) data studied by McCaffrey et al (2000) that suggested a uniform slip rate of 21 ± 5mm/year across central Sumatra. A geomorphology study on the SFZ by Sieh and Natawidjaja (2000) and Acocella et al (2018), found that it is highly segmented and can be divided into 19 major geometrically defined segments. Termed "equatorial bifurcation', the largest irregularity is located at the equator, where the fault separates into two subparellel branches at approximately 35 km apart (Sieh and Natawidjaja, 2000).…”