Transverse Tectonics in the Sikkim Himalaya: Evidence from Seismicity and Focal-Mechanism Data

Hazarika, Pinki; Kumar, M. Ravi; Srijayanthi, G.; Raju, P. V. Sunder; Rao, N. Purnachandra; Srinagesh, D.

doi:10.1785/0120090339

Cited by 68 publications

(39 citation statements)

References 13 publications

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“…Prior this event, damaging earthquakes occurred in 1849, 1852 and 1899 rarely exceeding seismic intensity of VIII MM. The focal mechanism of earthquakes in Sikkim shows that the tectonics of Himalaya in this region is dominated by large-scale strike slip motion (Hazarika et al 2010;Kayal et al 2010;Dasgupta et al 2013a;Pradhan et al 2013). The recent Sikkim earthquake (M w 6.9) of September 2011 with strike slip mechanism on a NNE-oriented fault showed its extension down to a depth of about 50 km implying deeper extension of lineaments and suggesting fragmentation of detachment surface in this region (Harward CMT solution).…”

Section: Sikkim-bhutan Seismic Gapmentioning

confidence: 99%

Discriminatory characteristics of seismic gaps in Himalaya

Srivastava¹,

Verma

Bansal

et al. 2013

Geomatics, Natural Hazards and Risk

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Contrary to most of the earlier theories that great earthquakes (M w 8.5 or even larger) may occur anywhere along the Indian plate boundary assuming uniform strain accumulation, this paper proposes two types of gaps with discriminatory characteristics. The new gaps were initially identified from earthquakes of magnitude 6, whose return periods in Himalaya vary between 20 and 30 years and are well within the period of reliable instrumental data of about 100 years. These gaps were then integrated with the largest magnitude event in instrumental era and historical times; information on paleoseismicity, micro-seismicity data, GPS-based geodetic observations and the tectonic features. The regions where great/major earthquakes (Mw 8 or larger) have occurred in the past are classified as seismic gap of category 1, namely Kashmir, west Himachal Pradesh (Kangra), Uttarakhand to Dharachulla, central Nepal to Bihar, Shillong, Arunachal gap including Assam-Tibet-Myanmar syntaxis. On the other hand, the second category of seismic gap includes JammuKishtwar block, east Himachal Pradesh, western Nepal (excluding Dharachulla region) and Sikkim-Bhutan where history of large earthquakes is not available. In these gaps, the largest earthquake magnitude is smaller (7-7.5) and the recurrence interval for earthquakes of same magnitude is larger as compared to category 1 gaps.

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Section: Sikkim-bhutan Seismic Gapmentioning

confidence: 99%

Discriminatory characteristics of seismic gaps in Himalaya

Srivastava¹,

Verma

Bansal

et al. 2013

Geomatics, Natural Hazards and Risk

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“…6), the fault plane with a right-lateral sense of slip is the one that best matches with the existing seismicity trend, regional fault in the vicinity and/or the known sense of fault/plate motion in the region. For instance, the right-lateral sense of plate motion is well known along the Sagaing fault (Curray et al 1979) and the Burmese arc (Rao and Kumar 1999;Rao and Kalpna 2005;Vigny et al 2003;Gahalaut and Gahalaut 2007), Kopili lineament (Vernant et al 2014) and Sikkim Himalaya (Hazarika et al 2010;Pradhan et al 2013;Fig. 2, in this paper).…”

Section: Transverse Tectonics In Sikkimmentioning

confidence: 53%

“…It can be seen that the horizontal EW gradients of the Bouguer anomalies around Sikkim reflect the general northerly orientations of the faults, with a strong NS anomaly of up to 3 mgal/km seen around 88°E, south of the MBT, consistent with the trend of Malda-Kishanganj fault in the Indo-Gangetic plains (GSI 2000). The extension of this fault into the Himalaya, and its role in controlling the transverse movements cannot be ruled out, although the trend of this fault does not match with the seismicity trends or the preferred fault plane which is more NW trending, consistent with the Tista/Gangtok lineaments (Hazarika et al 2010;De and Kayal 2003). The NE-trending Kanchenjunga fault (KF) in northern Sikkim having a perceptible gravity gradient, would also qualify to be the fault plane of the M w 6.9 Sikkim-Nepal earthquake of September 2011.…”

Section: Seismicity and Focal Mechanismsmentioning

confidence: 87%

“…These observations indicate a distinct scenario for the Sikkim Himalaya which could signify a transition from a simple India-Eurasia collision in the west to a more complex setting toward the Eastern Himalayan syntaxis zone. Local earthquake monitoring and analysis of focal mechanism solutions in the Sikkim region (Hazarika et al 2010;Kumar et al 2012) delineate NW-oriented fault trends consistent with those of the Tista and Gangtok lineaments. Similar seismicity trends have also been inferred by Velasco et al (2007) for the Sikkim-Bhutan region using data from a local seismic network.…”

Section: Sikkim Himalayamentioning

confidence: 99%

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The M w 6.9 Sikkim–Nepal earthquake of September 2011: a perspective for wrench faulting in the Himalayan thrust zone

et al. 2015

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In the present study, we analyze the strike-slip-type earthquakes along the Himalayan arc that are transverse to the collision front, with a special emphasis on the Sikkim region. The study examines seismicity and focal mechanism data in conjunction with crustal structure derived from receiver functions and gravity gradients, supported by results from GPS data. We present a relation between the north-south depth distribution of the strike-slip earthquakes in Sikkim, with the northward dipping trend of the Indian crust beneath Eurasia deciphered from teleseismic receiver function analysis of data recorded by our seismic network. Results suggest that transverse faults caused by thrust partitioning along the Himalayan arc manifest as vertical strike-slip faults cutting across the crust of the descending Indian plate down to 60 km. Further, we argue in favor of a consistent rightlateral sense of slip among all the strike-slip-type earthquakes cutting across the Himalayan arc from Kumaon in the west through Sikkim and Bhutan Himalaya, to the Burmese arc and the Sagaing fault on the easternmost end. We infer a wrench fault tectonic model for the Indian plate described by a series of right-lateral strike-slip faults from west to east in the Himalaya, in conjunction with under-thrusting of the Indian plate beneath Eurasia.

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“…The seismic activity is mainly clustered to the north of MBT with earthquakes occurring up to the depth of 50 km indicating a dominant control of MBT on the tectonics of the region (De and Kayal, 2004). A significant inference from various micro-seismic surveys carried out in the Sikkim Himalaya (De and Kayal, 2004;Nath et al, 2005;Hazarika et al, 2010) is that MBT is a seismogenic fault and it does not converge with the plane of detachment unlike in the western Himalaya but possibly traverses across the entire crust. Further, composite focal mechanisms show strike-slip nature of faulting or traverse tectonics, which does not match with the conceptual thrust tectonic models of the Himalaya.…”

Section: Introductionmentioning

confidence: 99%