羽绒棉Structural evolution and strike-slip tectonics off north-western Sumatra
Kai Berglar a ,⁎,Christoph Gaedicke a ,Dieter Franke a ,Stefan Ladage a ,Frauke Klingelhoefer b ,Yusuf S.Djajadihardja c
a Federal Institute for Geosciences and Natural Resources (BGR),Stilleweg 2,D-30655Hanover,Germany
b Ifremer Centre de Brest,B.P.70,29280Plouzanécedex,France
c
Agency for the Asssment &Application of Technology,Jl.M.H.Thamrin No.8,Jakarta 10340,Indonesia
a b s t r a c t
a r t i c l e i n f o Article history:
Received 22October 2008
Received in revid form 10July 2009Accepted 6October 2009
Available online 13October 2009Keywords:
Oblique subduction Strike-slip Forearc basin Sumatra烤虾怎么吃
Mentawai Fault Zone West Andaman Fault
Bad on new multi-channel ismic data,swath bathymetry,and diment echosounder data we prent a model for the interaction between strike-slip faulting and forearc basin evolution off north-western Sumatra between 2°N and 7°N.We examined ismic quences and a floor morphology of the Simeulue-and Aceh forearc basins and the adjacent outer arc high.We found that strike-slip faulting has controlled the forearc basin evolution since the Late Miocene.The Mentawai Fault Zone extends up to the north of Simeulue Island and was most probably connected farther northwards to the Sumatran Fault Zone until the end of the Miocene.Since then,this northern branch jumped westwards,initiating the West Andaman Fault in the Aceh area.The connection to the Mentawai Fault Zone is a left-hand step-over.In this transpressional tting the Tuba Ridge developed.We found a right-lateral strike-slip fault running from the conjunction of the West Andaman Fault and the Tuba Ridge in SSW-direction crossing the outer arc high.As a result,extrusion formed a marginal basin north of Simeulue Island which is tilted eastwards by uplift along a thrust fault in the west.The shift of
赵高之死strike-slip movement in the Aceh gment is accompanied by a relocation of the depocenter of the Aceh Basin to the northwest,forming one major Neogene unconformity.The Simeulue Basin bears two major Neogene unconformities,documenting that differences in subsidence evolution along the northern Sumatran margin are linked to both forearc-evolution related to subduction process and to deformation along major strike-slip faults.
©2009Elvier B.V.All rights rerved.
1.Introduction
Oblique convergence of colliding plates is a common feature at convergent margins.Partitioning of strain results in two major structural components:one that is perpendicular to the trench,reprented by folds and thrusts in the accretionary prism,and a cond component,accommodating the oblique convergence in strike-slip faults parallel to the trench (Beck et al.,1993;Beck,1983;Fitch,1972;Malod and Mustafa Kemal,1996;McCaffrey,1991).Examples of such strike-slip motions are the Liquine –Ofqui Fault (Cembrano et al.,1996)and Atacama Fault (Cembrano et al.,2005)in Chile or the Queen Charlotte/Fairweather fault system in Alaska (Dor and Lomas,2000).Studying such major strike-slip systems is crucial to understand the evolution of oblique margins and their behavior in terms of forearc basin evolution.
The study area is located off north-western Sumatra between 2°N and 7°N,covering the offshore region between the Mentawai Fault Zone and West Andaman Fault and the Sumatran Fault Zone (Fig.1).
Strong tectonic forces in fluence this area where the 2004M w 9.0Sumatra –Andaman and 2005M w 8.6Nias Island earthquakes nucleated (Engdahl et al.,2007).The right-lateral offshore fault systems and the onshore Sumatran Fault Zone accommodate the trench-parallel component of the oblique convergence between the Indo-Australian and the Eurasian Plates (Diament et al.,1992;Malod and Mustafa Kemal,1996;Samuel and Harbury,1996;Sieh and Natawidjaja,2000).The study area includes the Simeulue-and Aceh forearc basins and parts of the outer arc high.The studied basins show a change in water depth from about 1300m in the Simeulue Basin to about 2800m in the Aceh Basin and are clearly parated by an anticlinal structure that is elevated above the a floor and referred to as Tuba Ridge by Malod et al.(1993).
The main purpo of this work is the asssment of the structural evolution of the strike-slip fault system and its relation to the forearc basin evolution off northern Sumatra bad on the combined analysis of re flection ismic data,swath bathymetry and high resolution parametric echosounder data.The availability of a nearly complete swath bathymetric map in combination with a den grid of
ismic datats of different resolutions allows us to address the questions of when strike-slip movements started and if the movements have had a notable in fluence on the evolution of the forearc basins.Our data make it possible to distinguish the interaction of the Mentawai
启功书法作品Tectonophysics 480(2010)119–132
⁎Corresponding author.Bundesanstalt für Geowisnschaften und Rohstoffe,Federal Institute for Geosciences and Natural Resources,Stilleweg 2,D-30655Hanover,Germany.Tel.:+495116432149;fax:+495116433663.
E-mail address:kai.berglar@bgr.de (K.
Berglar).0040-1951/$–e front matter ©2009Elvier B.V.All rights rerved.doi:
10.2009.10.003
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Tectonophysics
j o u r n a l h o m e p a g e :w ww.e l s ev i e r.c o m /l o c a t e /t e c to
Fault Zone and the West Andaman Fault in the Simeulue area which is not yet fully understood.
2.Tectonic evolution of the western Sunda Arc
Along the Sunda arc the oceanic Indo-Australian Plate subducts beneath the continental Eurasian Plate.The rate and direction of convergence of the Indo-Australian Plate with respect to the Eurasian Plate show a decreasing and slightly anticlockwi trend from southeast to northwest (Fig.1).Bad upon GPS measurements Prawirodirdjo and Bock (2004)propod convergence rates of 61mm/y (N
17°E)off the Sunda Strait and 51mm/y (N11°E)off northern Sumatra.The plate motion model NUVEL-1A (DeMets et al.,1994)gives values of 70mm/y (N20°E)and 61mm/y
(N15°E)
Fig.1.Bathymetric map off northern Sumatra.Lines indicate positions of ismic ctions (Figs.3–10),boxes of detailed bathymetry (Fig.2).Land image is derived from SRTMv2data,light bathymetric background from the GEBCO One Minute Grid.The int shows the regional tectonic tting of the Sumatran subduction zone.IFZ =Investigator Fracture Zone.Sumatran Fault Zone (SFZ),Mentawai Fault Zone (MFZ),Batee Fault (BF),West Andaman Fault (WAF)and deformation front are bad on Sieh and Natawidjaja (2000).Ages of the oceanic crust are after Müller et al.(1997)and Deplus et al.(1998)in million years.Gray arrows indicate relative plate movements bad on NUVEL-1A (DeMets et al.,1994),black arrows bad on CGPS (Prawirodirdjo and Bock,2004).
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respectively.A clockwi rotation of Sumatra and Malaya of about20°relative to Eurasia since the Late Miocene(Ninkovich,1976; Nishimura et al.,1986)or Oligocene(Holcombe,1977)was caud by the collision and indentation of India into Eurasia(Daly et al.,1991; Longley,1997)and is the reason for a northward increasing obliquity of the subduction along the Sunda Arc.The curvature of the margin results in a plate convergence that gradually changes from nearly perpendicular subduction olearning
ff Java to highly oblique subduction off northern Sumatra(Moore et al.,1980).Along the north-western Sunda Arc strain partitioning and the development of arc-parallel strike-slip faults took place(Malod and Mustafa Kemal,1996).The most prominent strike-slip shear zone is the Sumatran Fault Zone located on the Sumatran mainland along the volcanic arc(Bellon et al., 2004)which forms the Barisan Mountains(Fig.1).The Sumatran Fault Zone accommodates most of the right-lateral strain of the relative plate motion and is propod to have been active since the Mid Miocene(McCarthy and Elders,1997).However,a distinct amount of arc-parallel strain is taken up by right-lateral strike-slip fault systems along the western edges of the forearc basins,namely the Mentawai Fault Zone and West Andaman Fault(Diament et al.,1992;Malod and Mustafa Kemal,1996;McCaffrey,1991).The Mentawai Fault Zone extends from the Sunda Strait in the south to at least the Island of Nias at about1.5°N where it is probably connected with the Sumatran Fault Zone along the Batee Fault(Milsom et al.,1995).Likely the Mentawai Fault Zone extends farther north into the Simeulue Basin(Diament et al.,1992).The West Andaman Fault extends southwards from the Andaman Islands to the Simeulue Basin along the western border of the Aceh Basin(Curray,2005).As pointed out by Curray et al.(1979) the Sumatran forearc acts as a sliver plate bounded to the west by the trench,below by the subducting plate,and to the east by the Sumatran Fault Zone.As a conquence the forearc sliver consists of elongated strips moving to the northwest.This was further refined by Ma
lod and Mustafa Kemal(1996)proposing two forearc microplates between the outer arc high and the Mentawai Fault Zone,parated by the Batee Fault.The western border of the northern microplate is reprented by the West Andaman Fault.
3.Methodology
We had approximately2800km of multi-channel ismic(MCS) data available in the study area from a total of more than9700km acquired during two rearch cruis with RV SONNE in2006.Shot distance was50m and we ud a digital240-channel streamer of3km length with a receiver spacing of12.5m,towed at a water depth of6m. The acoustic signal was generated by a tuned G-gun array of16units comprising a total volume of50.8l operated at air pressure of14.5MPa. Data were recorded with a sampling interval of2ms and14s length. Stacking velocities were picked at regular intervals of3km along every line.Pre-stack processing included resampling to4ms,trace editing, CMP-sort(nominal30-fold coverage,6.25m spacing),Ormsby band-passfilter(6–12–60–160Hz),polygon f–kfilter(window of60traces and1s length),zeropha spiking deconvolution(52ms operator length,1s design window beginning shortly below abottom reflection),amplitude correction for spherical divergence bad on stacking velocities(1/(t×v2)),normal moveout correction(40%stretch mute),and Radon velocityfilter for multiple suppression(rejecting velocities differing more than±20%of correspon
ding stacking velocity).After stacking we applied a space and time variant Ormsby bandpassfilter(upper window:10–20–60–100Hz,lower window:6–12–50–100Hz),a minimum pha predictive deconvolution and a post-stack Kirchhoff time migration with90%of stacking velocities.
Additionally,digitized scans converted to Segy-format from single-channel recordings acquired during the SUMENTA cruis in the early90s(Izart et al.,1994;Malod et al.,1993;Malod and Mustafa Kemal,1996)were available with a total length of about4800km in the study area.
Together with the MCS data,high resolution parametric echo-sounder data(difference frequency of3.5kHz)were recorded with the ATLAS PARASOUND system at a sampling rate of40kHz.The data were resampled to8kHz,bandpassfiltered(1.75–2.1–3.8–4kHz)and the envelope ismic attribute applied for visualization.
小苦瓜The swath bathymetric data is a compilation of Japane(Soh, 2006),British(Henstock et al.,2006;Tappin et al.,2007),French (Graindorge et al.,2008;Sibuet et al.,2007),American(RR0705, Crui Report,2007)and German(Ladage et al.,2006)datats recorded in the area during veral cruis.The bathymetric datats were provided either in different native binary multibeam-system formats or as dumped grid data in xyz-ASCII format.The data were ud as further e
diting was performed,and merged using the MB-System software package(Caress and Chayes,1996). For gridding,the different surveys were given priorities by a weighting scheme bad on aerial coverage and data quality to minimize artifacts and inconsistencies in regions of overlap.Gridding was performed with a grid spacing of100m and maps plotted with the GMT software package(Wesl and Smith,1991).
4.Structural analysis
The evaluated area off northern Sumatra covers three basin domains:The Aceh Basin,the Simeulue Basin and a smaller basin located northwest of Simeulue Island.For clarity,we introduce the name Tuba Basin for this depression(Fig.1).
A morphological analysis of the afloor bad on bathymetric data was carried out to identify tectonic structures.2-D MCS data were ud to determine the type and time of activity of the structures.We ud simultaneously recorded high-resolution echosounder data to verify if such structures affected the uppermost dimentary layers thus indicating recent activity.
4.1.Aceh Basin
The Aceh Basin is the northernmost forearc basin off Sumatra and is located in the conjunction between the West Andaman Fault and the Sumatran Fault Zone.It has a northward narrowing triangular shape covering an area of about6600km2with the northern tip reaching up to the island of Greater Nicobar(Fig.1).From there,the basin spans southward for about260km where it is bordered by the Tuba Ridge(Fig.1;Mosher et al.,2008).In E–W direction the basin has a width from the West Andaman Fault to the inner slope of about 65km.To the east,the inner slope leads over to the Sumatran mainland and,offshore the northern tip of Sumatra,the Sumatran Fault Zone.The basin isfilled with well stratified dimentary quences of an average thickness of2s two-way traveltime(TWT) that increas southwards.The architecture of the Aceh Basin is quite uniform in the south,while it becomes complex in the north.
The western border of the Aceh Basin is coincident with the West Andaman Fault.Bathymetry(Fig.2A)shows a NNW–SSE-striking, mainly linear feature with a well defined main fault and veral subordinate fault lines imaged as anticlines.The branch off into both the forearc basin and the outer arc high.The int in Fig.3shows the typical expression of the main fault line of the West Andaman Fault along the Aceh Basin,a small depressionfilled syntectonically with westward dipping diments,described in detail by Seeber et al.(2007). It is enframed at both sides b
y anticlines of about6km in width.The easternmost anticline is built up by the entire Neogene dimentary column of the Aceh Basin.The deformation affected the youngest diments indicating a recent activity of the West Andaman Fault,also evidenced by fault plane solutions(Kamesh Raju et al.,2007).
In the entire basin the ba of the well stratified diments is formed by a distinct unconformity(Figs.3–5).This unconformity is of regional extent and was probably caud by uplift and subquent erosion of the forearc area off Sumatra.It was interpreted in all forearc
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Fig.2.Detailed bathymetric maps of the study area.Letter order is from the NW to the SE (note different scale of maps).See Fig.1for location of maps and color scale.A:Aceh Basin.The West Andaman Fault (WAF)is a mainly linear feature with subordinate faults branching off both into the forearc basin and outer arc high.B:Southern Aceh-and northern Tuba Basins.The Tuba Ridge connects the West Andaman Fault and Mentawai Fault Zone (MFZ)through a left-hand step-over.A right-lateral strike-slip fault cuts the outer arc high resulting in extrusion of the northern Tuba Basin.C:Southern Tuba-and northern Simeulue Basins.The Mentawai Fault Zone developed a positive flower structure parating the basins.The Tuba Basin is tilted eastwards by uplift along a thrust fault at the western boundary.D:Western Simeulue Basin and part of Simeulue Island.Sigmoidal shaped anticlines indicate the main line of the Mentawai Fault Zone on the eastern shelf off Simeulue Island.Normal faults with SW –NE strike are located at the crest of a micircular uplifted area.E:Southwestern Simeulue Basin.The transition of the outer arc high to the basin is characterized by wrench-fault related anticlines.
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正确的洗头方法
Fig.3.MCS pro file across the central Aceh Basin.Older diments (A)are tilted westwards and the depocenter moved trenchward (B).The int illustrates the typical expression of the West Andaman Fault (WAF)in the Aceh gment.See Fig.1for location of pro fi
le.
Fig.4.MCS pro file across the southern Aceh Basin.Older basin diments (A)are uplifted and deformed by the West Andaman Fault (WAF),leaving little dimentation space for Sequence B.See Fig.1for location of pro file.
动漫素描图片123
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