Clusters of Moderate Size Earthquakes along Main Central Thrust (MCT) in Himalaya

Abstract

The Main Central Thrust (MCT) in Himalaya is seismically active in segments. In recent times, strain release within these active segments produce five spatial clusters (A to E; Figure 1). The seismicity within the cluster zones occurs in two depth bands; corresponding to the base of upper and lower crust. Depth sections across the clusters illustrate gently dipping subducted Indian Plate, overriding Tibetan Plate and compressed Sedimentary Wedge in between, with mid crustal ramping of MCT. Several presumptions / hypotheses have been put forward to decipher the causes of clustering along MCT. These are segmental activation of MCT, cross fault interactions, zones of arc parallel and arc perpendicular compressions, pore pressure perturbations, low heat flow zones etc. But these hypotheses need to be evaluated in the future after more ground level data are available. The maximum size of seismic threat that MCT can produce is inferred to be around Mw 7.0 in those clusters.

Reconstruction of Late Quaternary climate and seismicity using fluvial landforms in Pindar River valley, Central Himalaya, Uttarakhand, India

“…MCT is known for experiencing high crustal deformation (Seeber and Gornitz, 1983) due to which high compressive force causing the segmental reactivation of the transverse faults that are known to generate relatively high magnitude earthquakes in the region (Kayal et al, 2003;Mukhopadhyay, 2011). However around BjT, the higher incision/ uplift is ascribed to the activity along the BjT in the south and AT in the north and is schematically represented in Fig.…”

Finite element modelling of the 2015 Gorkha earthquake through the joint exploitation of DInSAR measurements and geologic-structural information

“…5c), due to the retrieved slip distribution (inset in Fig. 5c landslides, building collapses) [Ponraj et al, 2011;Mukhopadhyay 2011;Goda et al, 2015;Parameswaran et al 2015], our model results reveal a passive role of these structures; that is, the retrieved displacements in correspondence to the MCT and the MT zone can be explained as a possible mechanism for accommodating the MHT-sourced deformation on adjacent thrusts. Indeed, earlier studies suggest that the Himalayan earthquakes are associated with a fault-propagation folding that absorbs the deformations before they reach the surface, leaving no surface expressions of primary faulting [Yeats and Lillie, 1991]; accordingly, the hinterland structures may have played a role in accommodating the displacement field transferred from earthquakes originating on the MHT.…”

Identification of seismically susceptible areas in western Himalaya using pattern recognition

“…This aspect was used for segmentation of MCT (Mridula et al 2016, communicated). Seismogeological sections along Nanga Parbat syntaxes in the western Himalaya show a depth penetration of more than 200 km of the Indian plate (Mukhopadhyay 2011). Dasgupta et al (2013) illustrated that transverse tectonic features play an important role in the Himalayan collision, by studying the Sikkim earthquake of 18th September, 2011 and BiharNepal earthquake of 20th August, 1988.…”