Bearing of plate geometry and rheology on shallow-focus mega-thrust seismicity with special reference to 26 December 2004 Sumatra event

Khan, Prosanta Kumar; Chakraborty, Prithwish

doi:10.1016/j.jseaes.2008.07.006

Cited by 21 publications

(9 citation statements)

References 96 publications

(129 reference statements)

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“…Both mega‐shocks occurred in Sector V, and the maximum seismic energy was released through Sector V. We, therefore, explain our results in reverse order. Under pre‐seismic stress field (Figure ), the maximum compressive stresses (σ 1 ) in Sector V were acting along N200° in the early stage of deformation (T1, Table ) and changed to N230° in the later stage just prior to the occurrence of the 2004 mega‐event in the subducting plate, compatible with the inherited stress caused by the convergence of the Indo‐Australian Plate (see also Khan & Chakraborty, ). The stress regime also changed from semi‐radial compression (SRC) to pure compression (PC) over this duration.…”

Section: Discussionsupporting

confidence: 68%

Change of stress patterns during 2004 M_W 9.3 off‐Sumatra mega‐event: Insights from ridge–trench interaction for plate margin deformation

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The Andaman-Sumatra subduction margin is identified as a complex tectonic transition zone between the Myanmar and Java regions. The Late Cenozoic evolution of various basins, faults, plate slivers, and the Andaman back-arc rift-transform system altered the boundary. The sharp changes in free air gravity anomaly, north-eastward swing of the Andaman Sea spreading ridge, increased dip of the subducting plate and the decrease in seismicity towards the north of the study area possibly account for increased interaction of the Ninetyeast Ridge (NER) against the Andaman Trench.Stress fields of the subducting plate were modified from semi-radial compression (SRC) during pre-seismic deformation to pure extension (PE), semi-radial extension (SRE), and strike-slip extension (SSE) during post-seismic deformation phase in the central segment. The co-seismic second energy burst, subsidence in the overriding plate, and subsequent reactivation of the Barren and Narcondum volcanoes also corroborate the transformation of the stress fields in the overriding plate into predominant extension. The dominant SRC stress in the subducting Indo-Australian lithosphere in the south changed to pure compression (PC) prior to the 2004 M W 9.3 mega-event.While the changes in stress field from SRC to pure strike-slip (PSS) in the north account for stress relaxation after the occurrence of the mega-event and the co-seismic~1,300km rupturing, the occurrences of uplift and subsidence in the northern part of the study area were possibly caused by inherited stress field from the Eastern Himalaya.The continued overall compression in the subducting Indo-Australian Plate in the south, under pre-and post-seismic deformation phases, is presumably correlated with the focal mechanism stress parameters of the 2004 mega-event, whereas the strikeslip-dominated movement in the overriding plate remained almost unchanged. The stress perturbations in the central segment are interpreted to be the result of interaction between the NER and Andaman-Sumatra Trench.

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Section: Discussionsupporting

confidence: 68%

Change of stress patterns during 2004 M_W 9.3 off‐Sumatra mega‐event: Insights from ridge–trench interaction for plate margin deformation

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“…Turcotte and Schubert 65 showed that ~90% of elastic strain energy is released through flexing segment of the subducting lithosphere in form of seismicity, and ~10% is used for its supporting with hardly any deformation. Intraplate origin of such great earthquakes along the subduction margin was also proposed elsewhere [66][67][68] . The moment release characteristics during rupturing associated with the 25 April mainshock 69 clearly showed lower values for the initial ~15 sec, increasing gradually for the next ~10 sec, and later released drastically during remaining ~25 sec (Figure 2).…”

Section: Discussionmentioning

confidence: 55%

Insights into the Great <i>Mw</i> 7.9 Nepal Earthquake of 25 April 2015

2017

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The 2015 Mw 7.9 earthquake occurred in the Nepal Himalaya between the Indian and Asian plates. The gravity modelling has been carried out along a 2D trench-orthogonal profile passing through the epicentre of this earthquake. The projections of mainshocks and aftershocks show their major confinement around the bending segment of the Indian upper crust (IUC). The operative shallowly plunging maximum compressive stress led to the accumulation of strain energy around the bending zone of the IUC, and triggered thrust-dominated southward movement of the Indian crustal block along a shallowly, dipping shear plane in the anisotropic layer. This can be broadly explained by three-stage rupture processes: the first one was associated with slow nucleation and rupture growth for early ~15 sec, the second one migrated upward, rupturing the uppermost part of the IUC for the next ~10 sec, and the third one propagated very fast during deformation for the remaining ~25 sec till the fracture-tip reached the overlying brittle Asian crust.

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“…flexing zone) of the lithosphere experiences compressive stress field. This is presumably due to superposition of pulsating stresses on the long-term time average or steady bending stresses (Rice and Stuart 1989;Taylor et al 1996;Khan and Chakraborty 2009) along the longitudinal profile of the descending oceanic slab in Sumatra area (sector III). The pulsating periodic stress was clearly initiated from the uncompensated slab resistive force (Christensen and Ruff 1988;Astiz et al 1988;Lay et al 1989).…”

Section: Resultsmentioning

confidence: 99%

“…In this connection, Forsyth and Uyeda (1975) first suggested that the slab pull (F SP ) and slab resistive (F SR ) are the major plate-driving forces apparently control the dynamic equilibrium of the plates, and successfully explained the spatial variation of stress regime in the subducting oceanic lithosphere. They also invoked that F SP and F SR along the longitudinal profiles of the descending plate dictate the major intraplate failure for mega-earthquake generation (M W C 8.5) at the shallower level of the lithosphere (Forsyth and Uyeda 1975;Khan and Chakraborty 2009). Further, the flexing zone of the lithosphere beneath the trench during subduction suffers instability by the net effect of slab pull and slab resistive forces (Marotta and Mongelli 1998), and *60% of the energy associated with the subducting slab is normally dissipated through the bending segment of the slab (Conrad and Hager 1999).…”

Section: Introductionmentioning

confidence: 99%

“…Further, the flexing zone of the lithosphere beneath the trench during subduction suffers instability by the net effect of slab pull and slab resistive forces (Marotta and Mongelli 1998), and *60% of the energy associated with the subducting slab is normally dissipated through the bending segment of the slab (Conrad and Hager 1999). Invariably recorded shallowest dip, lowest flexing depth (Widiyantoro and Van der Hilst 1997;Khan and Chakraborty 2005), youngest plate age (*47 Ma in northwest Sumatra, increases to *152 Ma towards east near Java and *67 Ma towards north near North-Andaman, Muller et al 1997) of the subducting lithosphere, minimum slip vector residual (Liu et al 1995, Khan 2007, intermittent occurrence of megathrust earthquake (1797 M *8.4, 1833 M *9.0, 1861 M *8.5, Lay et al 2005; M w [ 9.0, 2005 M w 8.6, Ammon et al 2005, 9.3;Stein and Okal 2005), and recently proposed strain-hardened model for mega-earthquakes (Khan and Chakraborty 2009) allowed us for understanding the role of major plate-driving forces (Forsyth and Uyeda 1975) for the occurrence of 2004 off Sumatra event.…”

Section: Introductionmentioning

confidence: 99%

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Role of unbalanced slab resistive force in the 2004 off Sumatra mega-earthquake (M w > 9.0) event

Khan

2010

Int J Earth Sci (Geol Rundsch)

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Present study addresses the role of major platedriving forces, particularly the slab pull and slab resistive forces, for the generation of 26 December 2004 M w [ 9.0 off Sumatra megathrust earthquake. Major controls on the plate-driving forces are normally visualized through age, speed, and average dip of the slab during subduction. Wide variation in age, plate obliquity, stress obliquity, subduction rate, dip angle, and flexing depth of the subducting oceanic lithosphere between Andaman and Sumatra thus allowed us for quantitative evaluation of the slab pull (F SP ) and slab resistive (F SR ) forces in three well-defined sectors (I, II and III). Computed values of these forces in the three sectors: (1) F SP = 1.29 9 10 13 N/m, F SR = 1.41 9 10 13 N/m; sector I, (2) F SP = 2.10 9 10 13 N/m, F SR = 1.13 9 10 13 N/m; sector II, and (3) F SP = 2.08 9 10 13 N/m, F SR = 2.72 9 10 13 N/m; sector III clearly suggest a spatial variation of stress regime in the subducting oceanic lithosphere. Excess F SR in sectors I and III are interpreted as the causative forces behind the triggering of major seismic energy bursts near Sumatra and Andaman on 26 December 2004. A gap of minimum seismic energy burst near Great Nicobar possibly was controlled by the excess of F SP in sector II. This study further advocates that the cyclic stress, resulted from unbalanced component of slab resistive force, had a definite control on the occurrence of 2004 off Sumatra megathrust earthquake around the flexing zone of the subducting lithosphere.

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Bearing of plate geometry and rheology on shallow-focus mega-thrust seismicity with special reference to 26 December 2004 Sumatra event

Cited by 21 publications

References 96 publications

Change of stress patterns during 2004 M_W 9.3 off‐Sumatra mega‐event: Insights from ridge–trench interaction for plate margin deformation

Change of stress patterns during 2004 M_W 9.3 off‐Sumatra mega‐event: Insights from ridge–trench interaction for plate margin deformation

Insights into the Great <i>Mw</i> 7.9 Nepal Earthquake of 25 April 2015

Role of unbalanced slab resistive force in the 2004 off Sumatra mega-earthquake (M w > 9.0) event

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Bearing of plate geometry and rheology on shallow-focus mega-thrust seismicity with special reference to 26 December 2004 Sumatra event

Cited by 21 publications

References 96 publications

Change of stress patterns during 2004 MW 9.3 off‐Sumatra mega‐event: Insights from ridge–trench interaction for plate margin deformation

Change of stress patterns during 2004 MW 9.3 off‐Sumatra mega‐event: Insights from ridge–trench interaction for plate margin deformation

Insights into the Great <i>Mw</i> 7.9 Nepal Earthquake of 25 April 2015

Role of unbalanced slab resistive force in the 2004 off Sumatra mega-earthquake (M w > 9.0) event

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Change of stress patterns during 2004 M_W 9.3 off‐Sumatra mega‐event: Insights from ridge–trench interaction for plate margin deformation

Change of stress patterns during 2004 M_W 9.3 off‐Sumatra mega‐event: Insights from ridge–trench interaction for plate margin deformation