Barckhausen, U.

Flueh, Ernst R.

Gaedicke, C.

Klaeschen, Dirk

Kopp, Heidrun

Ladage, S.

Seacause and GITEWS Teams

Weinrebe, Reimer Wilhelm

Yusuf, M. D.

English

OceanRep

Geophysical Research Abstracts, Vol. 9, 07010, 2007SRef-ID: 1607-7962/gra/EGU2007-A-07010© European Geosciences Union 2007Lower plate impact on earthquake rupturesegmentation on the Sumatra marginH. Kopp (1), W. Weinrebe (1), S. Ladage (2), U. Barckhausen (2), D. Klaeschen (1),E. R. Flueh (1), C. Gaedicke (1), M. D. Yusuf (4) and the SeaCause and GITEWSTeams (1,2,3,4)(1) IFM-GEOMAR Leibniz-Institute of Marine Sciences, Kiel, Germany(hkopp@ifm-geomar.de)(2) BGR, Federal Institute for Geosciences and Natural Resources, Hannover, Germany(3) GFZ, GeoForschungsZentrum, Potsdam, Germany(4) BPPT, Agency for the Assessment and Application of Technology, Jakarta, IndonesiaThe large-scale morphotectonic segmentation of the Sumatra trench system resultsfrom subduction of reactivated fracture zones and aseismic ridges of the WhartonBasin and is also reflected in its seismotectonic segmentation as most recently evi-denced by the distinct rupture zones of the 2004-2005 earthquake couplet. The frac-ture zones and the aseismic Wharton Ridge represent tectonic segment boundaries andzones of anomalous crust with regards to density, crustal composition and thickness.The segmentation of the downthrusting plate is mirrored in the seismotectonics of theupper plate. The distinct rupture zones of the 1797/1833, 1861/2004 and 2005 megath-rust events suggest that tectonic overprint of the margin by subduction of oceanic re-lief and lithosphere anomalies leads to the formation of first-order segment boundarieson the upper plate that exert a decisive impact on earthquake rupture dynamics. Theextent of the 1797/1833, 1861/2004 and 2005 rupture zones shows an intriguing cor-relation to the segment boundaries. Though the scientific community is beginning tounderstand the role of segmentation on the extent and distribution of rupture duringmegathrust events, we still lack the full understanding of the weight and influenceof the physical properties of a margin (i.e. pore pressure, material strength, stressdistribution) on its seismic potential compared to its structural tectonic heterogene-ity. Upper plate segmentation of the Sumatra trench system is manifested in varyingmodes of mass transfer as revealed by high-resolution seafloor mapping. The marginsegments to the northwest of the Investigator Fracture Zone, which were affected bythe 2004 and 2005 megathrust earthquakes, are subject to extensive surface erosionof the margin wedge. Oversteepening of the lower slope in response to elevated porepressures and the subduction of pronounced seafloor topography lead to mass wastingprocesses here. Conversely, neotectonic formation of nascent accretionary thrust foldsis limited to the sections of the deformation front southeast of the Investigator Frac-ture Zone and documents the resumption of frontal sediment accretion in the wake ofoceanic relief subduction. Further analysis of multidisciplinary studies will close thegap in our ability to assess the impact of different physical-geological parameters onseismotectonic segmentation.

Lower plate impact on earthquake rupture segmentation on the Sumatra margin

Lower plate impact on earthquake rupture segmentation on the Sumatra margin

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