Nonlinear variations of the physical properties along the southern Ecuador subduction channel:: Results from depth-migrated seismic data

被引:65
作者
Calahorrano B., Alcinoe [2 ]
Sallares, Valenti [1 ]
Collot, Jean-Yves [2 ]
Sage, Francoise [2 ]
Ranero, Cesar R. [3 ]
机构
[1] CSIC, Inst Ciencia Mar CMIMA, Unidad Tecnol Marina, Barcelona 08003, Spain
[2] Univ Paris 06, CNRS, Univ Nice Sophia Antipolis, Inst Rech Dev, F-06235 Villefranche Sur Mer, France
[3] CSIC, Inst Ciencia Mar CMIMA, Inst Catalana Recerca Estudias Avancats, Barcelona 08003, Spain
关键词
subduction channel; velocity inversion; fluid overpressure; grain deformation;
D O I
10.1016/j.epsl.2007.11.061
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
We use two high-quality pre-stack depth-migrated multichannel seismic profiles acquired to quantify physical properties variations of underthrust sediments along the first similar to 30 km of subduction off the erosional southern Ecuadorian margin. Seismic data show three zones along the subduction channel (referred to as Zones I, II and III) characterized by distinct velocity and velocity-derived physical properties, which are in agreement with values estimated from experimental results of deformation in granular media. These three zones result from transformational changes of underthrust sediments governed by fundamentally different physical processes that control their mechanical behavior at increasing confining pressures. Based on our observations and its comparison with experimental results, we argue that the transformations undergone by underthrust sediments as they dip into the subduction zone are the following: within Zone I, progressively increasing velocity (and decreasing velocity-derived porosity) indicates continuous sediment compaction, which must be accompanied by effective fluid drainage along the decollement and/or across the accretionary wedge. The underthrust material is here unconsolidated from a mechanical point of view. Laboratory experiments indicate that the dominant processes at this range of pressures are grain rolling, particle rotation and frictional slip at grain contacts. Within Zone II, velocity (and porosity) remains constant for similar to 16 km (SIS-72) and similar to 12 km (SIS-18). This suggests undrained conditions resulting in growing fluid overpressure at the subduction channel. Grain deformation is similar to Zone I. Within Zone III, velocity increases and porosity falls rapidly, indicating sediment compaction and subsequent release of over-pressured fluids, where grain deformation is likely to be elastic. This might be the dominant process until the grains attain their crushing strength, resulting in granular cataclasis and, eventually, in the collapse of the system. We suggest that over-pressured fluid release may induce hydrofracturation and it is likely to increase inter-plate coupling down from Zone III. (C) 2007 Elsevier B.V. All rights reserved.
引用
收藏
页码:453 / 467
页数:15
相关论文
共 93 条
[1]  
AGUFRLO E, 2006, IMAGERIE SISMIQUE QU
[2]  
Athy L.F., 1930, B AM ASS PET GEOL, V14, P1
[3]   Evolution of the Nankai Trough decollement from the trench into the seismogenic zone: Inferences from three-dimensional seismic reflection imaging [J].
Bangs, NL ;
Shipley, TH ;
Gulick, SPS ;
Moore, GF ;
Kuromoto, S ;
Nakamura, Y .
GEOLOGY, 2004, 32 (04) :273-276
[4]   Fluid accumulation and channeling along the northern Barbados Ridge decollement thrust [J].
Bangs, NLB ;
Shipley, TH ;
Moore, JC ;
Moore, GF .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1999, 104 (B9) :20399-20414
[5]   SEISMIC VELOCITIES FROM THE BARBADOS RIDGE COMPLEX - INDICATORS OF HIGH PORE FLUID PRESSURES IN AN ACCRETIONARY COMPLEX [J].
BANGS, NLB ;
WESTBROOK, GK ;
LADD, JW ;
BUHL, P .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH AND PLANETS, 1990, 95 (B6) :8767-8782
[6]   Revised tectonic boundaries in the Cocos Plate off Costa Rica: Implications for the segmentation of the convergent margin and for plate tectonic models [J].
Barckhausen, U ;
Ranero, CR ;
von Huene, R ;
Cande, SC ;
Roeser, HA .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 2001, 106 (B9) :19207-19220
[7]   Using the OBS wide-angle reflection/refraction velocities to perform a pre-stack depth migration image of the "single bubble" multichannel seismic:: example of the Moroccan margin [J].
Bartolome, R ;
Contrucci, I ;
Nouzé, H ;
Thiebot, E ;
Klingelhoëfer, F .
JOURNAL OF APPLIED GEOPHYSICS, 2005, 57 (02) :107-118
[8]   THE RELATIONSHIP BETWEEN SEISMIC VELOCITY AND DENSITY IN THE CONTINENTAL-CRUST - A USEFUL CONSTRAINT [J].
BARTON, PJ .
GEOPHYSICAL JOURNAL OF THE ROYAL ASTRONOMICAL SOCIETY, 1986, 87 (01) :195-208
[9]  
BOLOTN AJ, 2000, P ODP SCI RESULTS, V170
[10]   THE TECTONIC FABRIC OF THE BARBADOS RIDGE ACCRETIONARY COMPLEX [J].
BROWN, KM ;
WESTBROOK, GK .
MARINE AND PETROLEUM GEOLOGY, 1987, 4 (01) :71-81