Deformation, earthquakes and tsunamis along thickly sedimented subduction: Arakan segment of the Sunda Arc

2021 ◽  
Author(s):  
Cecilia McHugh ◽  
Leonardo Seeber ◽  
Michael Steckler ◽  
Syed Humayun Akhter ◽  
Nickolas Dubin
Keyword(s):  
Shallow Water ◽  
Accretionary Prism ◽  
Live Coral ◽  
Sediment Thickness ◽  
Marine Terraces ◽  
Sunda Arc ◽  
Seismic Surveying ◽  
Splay Faults ◽  
Anelastic Deformation ◽  
Subbottom Profiling

<p>Incoming sediment thickness and composition are primary factors in the morphology and shallow structure of subduction boundaries. Sediment thickness in the Indian Ocean increases SE to NW along the Sunda arc. From <1km along Java to >15km where the boundary encounters the Ganges-Brahmaputra Delta (GBD). Here the accretionary prism broadens to the NW to >300 km wide. It is dominated by shallow-water to non-marine sediment. This segment also features a broad shallow megathrust overlain by linear anticlines rooted in splay faults. It is entirely above sea level and blind in its frontal part. This GBD segment transitions to a more familiar subduction structure and morphology along the submerged Arakan segment to the SE. The SE portion of this segment is characterized by larger splay faults that expose deep-water sediment with mud diapirism forming volcanoes and circular synclines. With increasing sediment input, the NW portion of the Arakan segment encroaches onto the GBD shelf. Both the SE and NW portions of the Arakan segment ruptured in the Mw>8.5 1762 tsunamigenic earthquake according to field and modeling evidence.</p><p>Uplifted coral reefs and marine terraces along the Myanmar and Bangladesh coasts document a >500 km rupture in 1762. The uplift, ranging from 6 m to 2 m from south to north, has been linked to rupture on the megathrust and on shallow splays. Tsunami deposits are traced for ~10 km along the St. Martin’s Island anticline and for >40 km along the Teknaf peninsula. Microfossils and mollusk assemblages in these deposits are consistently of shallow water affinity and date the tsunami to 1762. This deposit covers only a small fraction of the inferred megathrust rupture. If it is representative of the total tsunami distribution, a local anticline may have been the main source. Evidence from live coral microatolls show uplift on St. Martin’s Island continuing 250 years after the earthquake. This motion could stem from continued anelastic deformation of the anticline updip of the rupture. More widely distributed evidence from sediment and corals could address questions about megathrust and splay behavior in 1762 and after. Plans include multichannel seismic surveying, high resolution subbottom profiling and 40 m long piston coring to compare the SE to NW shelf portions to the Arakan segment along the Myanmar and Bangladesh coasts. More generally, we aim to better understand subduction and geohazards along thickly sedimented systems.</p>

scholarly journals Estimation of surficial sediment thickness using mid-frequency ocean acoustic bottom reflected signals measured in shallow water off Geoje island

2016 ◽  
Vol 35 (6) ◽  
pp. 419-426
Author(s):  
Hyuckjong Kwon ◽  
Jee Woong Choi ◽  
Su-Uk Son ◽  
Sungho Cho ◽  
Jooyoung Hahn ◽  
...  
Keyword(s):  
Shallow Water ◽  
Surficial Sediment ◽  
Sediment Thickness

scholarly journals ACCURACY OF UNSUPERVISED CLASSIFICATION TO DETERMINE CORAL HEALTH USING SPOT-6 AND SENTINEL-2A

2019 ◽  
Vol XLII-4/W16 ◽  
pp. 503-509 ◽  
Author(s):  
N. Nurdin ◽  
M. Lanuru ◽  
M. Akbar AS ◽  
I. Kartika ◽  
T. Komatsu ◽  
...  
Keyword(s):  
Shallow Water ◽  
Accuracy Assessment ◽  
Unsupervised Classification ◽  
Live Coral ◽  
Natural Death ◽  
Dead Coral ◽  
Reflectance Analysis ◽  
Coral Health ◽  
Ground Truthing ◽  
Sentinel 2A

Abstract. Characteristics of corals spectral from different species are expected to have optically different characters. The aims of this research are to compare unsupervised classification between IsoData and K-Means methods with Lyzenga application, and to analyze the precision of SPOT-6 and Sentinel-2A satellite imagery in classsifying shallow water habitat. The image processing are atmosferic correction, cropping, masking, Depth Invariant Index, Unsupervised classification, ground truthing, reclassify, accuracy assessment, and shallow water habitat spectral reflectance analysis. Rubble and dead coral with algae were indicating as coral death due to either damaging human activity or natural death such as bleaching. The accuracy of unsupervised classification IsoData and K-Means method have the same accuracy 62.50%. The IsoData method is better detected live coral and algae. Rubble were dominant detected in K-Means method.

Origin and emplacement of an inferred late Jurassic subduction-accretion complex, Euboea, eastern Greece

1991 ◽  
Vol 128 (1) ◽  
pp. 27-41 ◽  
Author(s):  
A. H. F. Robertson
Keyword(s):  
Shallow Water ◽  
Subduction Zone ◽  
Late Jurassic ◽  
Carbonate Platform ◽  
Accretionary Prism ◽  
Oceanic Lithosphere ◽  
Passive Margin ◽  
Late Triassic ◽  
Accretionary Complex ◽  
Alkali Basalts

AbstractIn northern Euboea, central eastern Greece, an up to 3 km-thick polygenetic melange (Pagondas complex) is structurally interleaved between a Triassic–Jurassic carbonate platform (Pelagonian Zone) and an overriding harzburgitic ophiolite. The melange mainly comprises late Triassic shallow-water limestone and calciturbidites, radiolarites, Triassic–Jurassic tholeiites, alkaline basalts and minor andesites. The units concerned range from kilometre-sized thrust sheets, and detached blocks, to broken formation and structureless, or bedded matrix-supported conglomerates (diamictite). The melange includes remnants of Neotethyan oceanic lithosphere, overlain by radiolarites, hemipelagic carbonates and distal calciturbidites derived from a Mesozoic carbonate platform. Tholeiites were erupted at a Triassic–Jurassic spreading axis, whilst within-plate-type alkali basalts are interpreted mainly as seamounts. Kilometre-scale detached blocks of shallow-water coralline limestone are identified as collapsed atolls, formed within an ocean and/or along the rifted continental margin. Volcaniclastic sediments are locally interbedded with radiolarite, and reflect post-volcanic erosion of the ocean floor. Intra-oceanic convergence began, apparently in late early Jurassic time, giving rise to the Euboea ophiolite above an inferred westwards-dipping subduction zone. The Pagondas Complex then developed as an accretionary prism. The subduction trench later collided with the Pelagonian passive margin, driving the hot Euobea ophiolite over the accretionary complex, to produce amphibolites and greenschists of the metamorphic sole. Trench–margin collision then drove the entire supra-subduction zone complex, apparently eastwards, downflexing the Pelagonian carbonate platform to form a foredeep in which late Jurassic (Kimmeridgian–Tithonian) radiolarian sediments accumulated. During emplacement, the accretionary complex was disrupted and partly resedimented as debris flows, turbiditic volcaniclastic sandstone and shale in a foredeep, or foreland basin setting.

scholarly journals THE BOTTOM SUBSTRATE SHALLOW WATER MAPPING USING THE QUICK BIRD SATELLITE IMAGERY

2010 ◽  
Vol 2 (1) ◽  
Author(s):  
Vincentius Siregar
Keyword(s):  
High Resolution ◽  
Shallow Water ◽  
Transformation Method ◽  
Live Coral ◽  
Bottom Substrate ◽  
Accuracy Test ◽  
Coral Sand ◽  
Water Mapping ◽  
Macro Algae

<p>The objective of this study was to explore the capability of high resolution satellite data of QuicBird to map the characteristics of the bottom shallow water (habitat) using the transformation method of two bands (blue and green) by implementing "depth invariant index" algorithm i.e., Y = ln Band 1 - (ki/kj) ln Band 2. The result provide more detail information on the characteristic of the bottom shallow water comparing to the used of original band (RGB). The classification of the transformed image showed 6 classes of bottom substrats i.e., Live coral, Death, Coral, Sand mix coral, Sand mix algae, and<br />Macro algae with Sand. The accuracy test of the map derived from the classification was about 79%.</p><p>Keywords: bottom shallow water, Quick Bird image, depth invariant index, classification</p>

scholarly journals THE BOTTOM SUBSTRATE SHALLOW WATER MAPPING USING THE QUICK BIRD SATELLITE IMAGERY

2010 ◽  
Vol 2 (1) ◽  
Author(s):  
Vincentius Siregar
Keyword(s):  
High Resolution ◽  
Shallow Water ◽  
Satellite Imagery ◽  
Transformation Method ◽  
Live Coral ◽  
Bottom Substrate ◽  
Accuracy Test ◽  
Coral Sand ◽  
Water Mapping

The objective of this study was to explore the capability of high resolution satellite data of QuicBird to map the characteristics of the bottom shallow water (habitat) using the transformation method of two bands (blue and green) by implementing "depth invariant index" algorithm i.e., Y = ln Band 1 - (ki/kj) ln Band 2. The result provide more detail information on the characteristic of the bottom shallow water comparing to the used of original band (RGB). The classification of the transformed image showed 6 classes of bottom substrats i.e., Live coral, Death, Coral, Sand mix coral, Sand mix algae, andMacro algae with Sand. The accuracy test of the map derived from the classification was about 79%.Keywords: bottom shallow water, Quick Bird image, depth invariant index, classification

scholarly journals Seismic images of the Northern Chilean subduction zone at 19°40′S, prior to the 2014 Iquique earthquake

2021 ◽  
Vol 225 (2) ◽  
pp. 1048-1061
Author(s):  
Ina Storch ◽  
Stefan Buske ◽  
Pia Victor ◽  
Onno Oncken
Keyword(s):  
Subduction Zone ◽  
Root Zone ◽  
Accretionary Prism ◽  
Depth Image ◽  
Plate Interface ◽  
Data Set ◽  
Nazca Plate ◽  
Depth Migration ◽  
Splay Faults ◽  
Splay Fault

SUMMARY The Northern Chilean subduction zone is characterized by long-term subduction erosion with very little sediment input at the trench and the lack of an accretionary prism. Here, multichannel seismic reflection (MCS) data were acquired as part of the CINCA (Crustal Investigations off- and onshore Nazca Plate/Central Andes) project in 1995. These lines cover among others the central part of the MW 8.1 Iquique earthquake rupture zone before the earthquake occurred on 1 April 2014. We have re-processed one of the lines crossing the updip parts of this earthquake at 19°40′S, close to its hypocentre. After careful data processing and data enhancement, we applied a coherency-based pre-stack depth migration algorithm, yielding a detailed depth image. The resulting depth image shows the subduction interface prior to the Iquique megathrust earthquake down to a depth of approximately 16 km and gives detailed insight into the characteristics of the seismogenic coupling zone. We found significantly varying interplate reflectivity along the plate interface which we interpret to be caused by the comparably strong reflectivity of subducted fluid-rich sediments within the grabens and half-grabens that are predominant in this area due to the subduction-related bending of the oceanic plate. No evidence was found for a subducted seamount associated to the Iquique Ridge along the slab interface at this latitude as interpreted earlier from the same data set. By comparing relocated fore- and aftershock seismicity of the Iquique earthquake with the resulting depth image, we can divide the continental wedge into two domains. First, a frontal unit beneath the lower slope with several eastward dipping back-rotated splay faults but no seismicity in the upper plate as well as along the plate interface. Secondly, a landward unit beneath the middle slope with differing reflectivity that shows significant seismicity in the upper plate as well as along the plate interface. Both units are separated by a large eastward dipping mega splay fault, the root zone of which shows diffuse seismicity, both in the upper plate and at the interface. The identification of a well-defined nearly aseismic frontal unit sheds new light on the interplate locking beneath the lower continental slope and its controls.

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