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  • 1
    Publication Date: 2011-06-01
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
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  • 2
    Publication Date: 2010-07-01
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
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  • 3
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 4
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 5
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    In:  [Poster] In: AGU Fall Meeting 2009, 14.-18.12, San Francisco, USA .
    Publication Date: 2012-02-23
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 6
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    In:  [Talk] In: AGU Fall Meeting 2011, 05.12.-09.12.2011, San Francisco, California, USA .
    Publication Date: 2012-02-23
    Description: ABSTRACT FINAL ID: T21E-04 We have studied submarine land-sliding using a seafloor topography and side-scan sonar data along the continental slope of the Middle America Trench. This subduction zone is dominated by tectonic erosion. Studies during the last few decades have shown mass wasting structures at submarine slopes around the world’s continental margins, hot-spot volcanic islands, and volcanic island arcs. At Atlantic margins slides initiate at low slope angles and appear triggered by high sediment accumulation rates. At volcanic islands large-scale land-sliding is caused by volcano sector collapse. At subduction zones with accretionary prisms, land-sliding seems associated to contractional tectonics and fluid seepage. Submarine mass movements at subduction zones dominated by tectonic erosion are comparatively limited. However, tectonic erosion is active in about 50% of the world subduction zones. Distinct failures have been studied at slopes in Peru, Costa Rica, Nicaragua and New Zealand but extensive surveys have not been obtained. We present a comprehensive data sets on seafloor mapping on a subduction zone dominated by tectonic erosion. The data covers much of the Middle America Trench (MAT) from the Mexico-Guatemala border to Costa Rica – Panama border. The goal of this contribution is to evaluate how long-term tectonics caused by subduction erosion preconditions the continental slope structure to modulate the generation of land-sliding. We show that changes in subduction erosion processes, interacting with the local topography of the subducting plate correlate to variations in the type and distribution of failures along the slope of the region.
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 7
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    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität zu Kiel, Kiel, XVI, 111 pp
    Publication Date: 2016-10-14
    Description: This Thesis work presents a regional-scale study of submarine mass-wasting phenomena of the continental slope of a subduction zone. The nature of the study makes it a new, outstanding contribution for two main reasons: 1) The large-scale and interdisciplinary characters of the study conform a comprehensive investigation - unmatched by any other previous study- of land sliding processes along the slope of a tectonically-active convergent margin. 2) The investigation is also unique because it looks into the processes at a subduction zone dominated by tectonic erosion. This type of geological setting represents about 50% of the world subduction zone systems, but it has been overlooked in previous studies of mass wasting processes. The study region is located along a segment of the Middle America Trench (MAT) that extends about 1500 km from the Costa Rica - Panama border to the Guatemala - Mexico boundary. The study investigates the structures of the continental slope of the Pacific-Ocean-side of Central America and the trench-region of the incoming oceanic Cocos plate. We have investigated the distribution of submarine slope failures and their deposits, the type of failures, and their seafloor morphology. We have also investigated possible preconditioning and triggering mechanisms, and the relationship of those mechanisms and the variability in failure type to the tectonic processes of this particular geological setting. Finally, we have made some inferences of the significance of mass wasting processes in the long-term evolution of the slope, compared to other geological settings. The Central America subduction zone has been the locus of intense, continued geoscientific investigation since the late 1970s that culminated with the selection of the region as the focus site for the US-Margins program and the German SFB574 during the first decade of the 21st century. Those two programs included research in a broad range of topics that attempted to advance our understanding of the entire subduction zone system. As a result numerous projects from both communities have benefited from close collaborations. This PhD work is integrated within the research project SFB 574, financed by the DFG, that has as main research goal investigations on “Volatiles and fluids in subduction zones and their impact on climate feedback and trigger mechanisms for natural disasters”. We have analyzed a database containing a compilation of multibeam bathymetry of 7 research cruises, 3 cruises of side-scan sonar imagery and core samples of a dedicated cruise. The database has been assembled in a collaborative effort between both USMargins and SFB 574 communities. Based on seafloor morphology and backscatter imagery, and seismic images we have mapped and classified 147 submarine slope failures in the region. Slope failures vary in their type, abundance and distribution along and across the slope to define six distinct segments along the MAT. The lateral extent of the six segments correlates well with similar along-trench segmentation in the character of the incoming ocean plate, expressed as changes in its relief, age and crustal thickness. We have also found that the six along-margin segments display changes in the across-slope structuring of the different geological elements, including changes in the morphological expression of upper, middle and lower slope, total slope width, and slope dip angle. This structuring of the elements of the slope appears to be related to a longterm evolution caused by the tectonic processes associated to subduction erosion. One segment covers the area of under-thrusting of Cocos Ridge under the shelf-slope offshore Osa Peninsula (southern Costa Rica). Here, 1-km-high narrow, sharp ridges and small conical seamounts festooning Cocos Ridge cause slumps often with rock and debris avalanches from a short, steep continental slope. A second segment occurs offshore central Costa Rica, where large conical seamounts and ridges of 1-3 km high and 40 km wide under-thrust the continental slope causing large re-entries of the slope toe, and furrows across the slope formed by collapse, of previously uplifted upper plate, along steep headwalls behind the under-thrusting seamounts. Failures have generated large slumps, debris flows and rock avalanches containing blocks up to 500 m in diameter. In contrast at a third segment in northern Costa Rica, offshore the North Nicoya Peninsula, a smooth incoming plate is parallel opposite by a continental slope lacking relevant mass wasting structures. The contiguous fourth segment offshore Nicaragua displays a steep middle slope with large translational slides opposite an ocean plate with numerous 1-km-tall seamounts and 100s-meter-high horst and graben relief. Under the fifth segment, offshore El Salvador, subducts a well developed horst and graben relief, but somewhat surprising the segment displays a generally failure-free slope, and only the uppermost slope displays a series of small translation slides The plate under-thrusting the sixth segment offshore Guatemala is similarly characterized by a horst and graben terrain. However, here a steeper slope exhibits frequent, small-scale failures, a few km wide, across the entire segment.
    Type: Thesis , NonPeerReviewed
    Format: text
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  • 8
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    In:  [Poster] In: ESF Research Conference on Understanding Extreme Geohazards, 27.11.-02.12.2011, Sant Feliu de Guixols, Spain .
    Publication Date: 2019-09-23
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 9
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    AGU (American Geophysical Union)
    In:  Geochemistry, Geophysics, Geosystems, 11 (5).
    Publication Date: 2019-09-23
    Description: Submarine slope failures occur at all continental margins, but the processes generating different mass wasting phenomena remain poorly understood. Multibeam bathymetry mapping of the Middle America Trench reveals numerous continental slope failures of different dimensions and origin. For example, large rotational slumps have been interpreted to be caused by slope collapse in the wake of subducting seamounts. In contrast, the mechanisms generating translational slides have not yet been described. Lithology, shear strength measurements, density, and pore water alkalinity from a sediment core across a slide plane indicate that a few centimeters thick intercalated volcanic tephra layer marks the detachment surface. The ash layer can be correlated to the San Antonio tephra, emplaced by the 6000 year old caldera-forming eruption from Masaya-Caldera, Nicaragua. The distal deposits of this eruption are widespread along the continental slope and ocean plate offshore Nicaragua. Grain size measurements permit us to estimate the reconstruction of the original ash layer thickness at the investigated slide. Direct shear test experiments on Middle American ashes show a high volume reduction during shearing. This indicates that marine tephra layers have the highest hydraulic conductivity of the different types of slope sediment, enabling significant volume reduction to take place under undrained conditions. This makes ash layers mechanically distinct within slope sediment sequences. Here we propose a mechanism by which ash layers may become weak planes that promote translational sliding. The mechanism implies that ground shaking by large earthquakes induces rearrangement of ash shards causing their compaction (volume reduction) and produces a rapid accumulation of water in the upper part of the layer that is capped by impermeable clay. The water-rich veneer abruptly reduces shear strength, creating a detachment plane for translational sliding. Tephra layers might act as slide detachment planes at convergent margins of subducting zones, at submarine slopes of volcanic islands, and at submerged volcano slopes in lakes.
    Type: Article , PeerReviewed
    Format: text
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  • 10
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    Springer International Publishing
    In:  In: Submarine Mass Movements and Their Consequences: 6th International Symposium. Advances in Natural and Technological Hazards Research, 37 . Springer International Publishing, Cham, pp. 165-175. ISBN 978-3-319-00971-1
    Publication Date: 2017-03-22
    Description: We use complete inventories of submarine landslides from the Middle America (MA) and the Central Chile (CC) trench and forearc systems to analyze the size-frequency relationship of such structures on active continental slopes. The MA forearc is characterized by subduction erosion, and the CC forearc has had an accretionary tectonic history since the Late Neogene. Both are end-member types of convergent margins around the world. Both margin segments have been mapped by high-resolution swath bathymetry at strike lengths of about 1,300 km (MA) and 1,000 km (CC). The Middle America forearc has 143 discernible slides with sizes ranging from 0.38 to 1,426 km2. Offshore Central Chile, the 62 mapped slides are 0.9–1,285 km2 in size. Slide localization is markedly different at both margin types. While they also vary strongly along strike of the individual margin, depending on forearc slope gradient, kinematic coupling between plates, or topographic structure of the downgoing plate, the size-frequency relationships are remarkably similar. This allows quantification of the incidence of a submarine slide of given size per margin segment. The relationships hold for slide sizes from 10 to 1,000 km2, with the cut-off defined by slide size (smaller slides) and sample size (larger slides). As slide traces of 100–300 km2 size are obliterated by tectonic deformation after about 200,000 years, recurrence rates for slides of a given size can be estimated. This offers a chance to assess hazard and risk resulting from such events. It is suggested that it takes 20 to 200 plate boundary earthquakes to set off a medium-sized (〉10 km2) or larger slump or slide.
    Type: Book chapter , NonPeerReviewed
    Format: text
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