Oblique convergence and slip partitioning in the NW Himalaya: Implications from GPS measurements

Abstract

We report GPS measurements of crustal deformation across the Kashmir Himalaya. We combined these results with the published results of GPS measurements from the Karakoram fault system and suggest that in the Kashmir Himalaya, the motion between the southern Tibet and India plate is oblique with respect to the structural trend. We estimated this almost north-south oblique motion to be 17 ± 2 mm/yr, which is partitioned between dextral motion of 5 ± 2 mm/yr on the Karakoram fault system and oblique motion of 13.6 ± 1 mm/yr with an azimuth of N198°E in the northwest-southeast trending Kashmir Himalayan frontal arc. Thus, the partitioning of the India-Southern Tibet oblique motion is partial in the Kashmir Himalayan frontal arc. However, in the neighboring Nepal Himalaya, there is no partitioning; the entire India-Southern Tibet motion of 19-20 mm/yr is arc normal and is accommodated entirely in the Himalayan frontal arc. The convergence rate in the Kashmir frontal Himalaya is about 25% less than that in the Nepal Himalayan region. However, here the Karakoram fault system accommodates about 20% of the southern Tibet and Indian plate convergence and marks the northern extent of the NW Himalayan arc sliver. The Kaurik Chango rift, a north-south oriented seismically active cross-wedge transtensional fault appears to divide the sliver in two parts causing varying translatory motion on the Karakoram fault on either side of the Kaurik Chango rift.

The 2015 Gorkha earthquake investigated from radar satellites: slip and stress modeling along the MHT

“…In this work we utilized different InSAR data to create a detailed image of the earthquake mainshock and its largest aftershock. We find that slip is slightly oblique, i.e., with a dextral component, and exceeds a peak thrust slip of about 5.2 m. The slight oblique nature of the MHT is in line with long term GPS observations, also revealing a dextral motion component (Kundu et al, 2014). The Kathmandu city is overlaying the region of the highest slip to the south (Figure 5), but no primary fault ruptures have been observed in town, or at any of the main thrusts (MFT, MBT, MCT), neither by eyewitness accounts nor in our InSAR data.…”

Overestimation of the earthquake hazard along the Himalaya: constraints in bracketing of medieval earthquakes from paleoseismic studies

“…The decrease in the slip rates along the frontal Himalayan arc is attributed to the counter-clockwise rotation of the Indian plate with respect to the stable Eurasian plate (Bilham et al 2001). In addition, other probable reasons could be oblique convergence (Malik and Nakata 2003;Malik et al 2015;Kundu et al 2014). …”

“…India-Eurasia convergence is arc normal in the Central Himalaya, but to the west, it becomes oblique to the regional Himalayan structural trend (Malik and Nakata 2003;Kundu et al 2014). This obliquity results in a shear component, which is manifested in the form of strikeslip faults.…”

Can an earthquake of M w ∼9 occur in the Himalayan region?

“…The width of the locked zone may be reliable in central Nepal (width 80-100 km; Ader et al 2012), where there are large numbers of GPS measurements, but it may not be reliable elsewhere (e.g. in the Kashmir Himalaya; Schiffman et al 2013;Kundu et al 2014), where it has been derived from a very limited number of site measurements. Nevertheless, there is unambiguous evidence of strain accumulation along all the Himalayan arc, although it is again difficult to quantify the total amount of accumulated strain in each Himalayan segment and whether it will be released in a major, great or giant earthquake.…”