Modelling for Science, for a better future - some recent outcomes
India plate angular velocity and contemporary deformation rates from continuous GPS measurements from 1996 to 2015
by Sridevi Jade, T. S. Shrungeshwara, Kireet Kumar, Pallabee Choudhury, Rakesh K. Dumka and Harsh Bhu
We estimate a new angular velocity for the India plate and contemporary deformation rates in the plate interior and along its seismically active margins from Global Positioning System (GPS) measurements from 1996 to 2015 at 70 continuous and 3 episodic stations. A new India-ITRF2008 angular velocity is estimated from 30 GPS sites, which include stations from western and eastern regions of the plate interior that were unrepresented or only sparsely sampled in previous studies. Our newly estimated India-ITRF2008 Euler pole is located significantly closer to the plate with ~3% higher angular velocity than all previous estimates and thus predicts more rapid variations in rates and directions along the plate boundaries. The 30 India plate GPS site velocities are well fit by the new angular velocity, with north and east RMS misfits of only 0.8 and 0.9 mm/yr, respectively. India fixed velocities suggest an approximate of 1–2 mm/yr intra-plate deformation that might be concentrated along regional dislocations, faults in Peninsular India, Kachchh and Indo-Gangetic plain. Relative to our newly-defined India plate frame of reference, the newly estimated velocities for 43 other GPS sites along the plate margins give insights into active deformation along India’s seismically active northern and eastern boundaries.
Source: https://www.nature.com/articles/s41598-017-11697-w
Parameterization of water vapor using high-resolution GPS data and empirical models
by Shantikumar S.Ningombam, Sridevi Jade and T.S.Shrungeshwara
The present work evaluates eleven existing empirical models to estimate Precipitable Water Vapor (PWV) over a high-altitude (4500 m amsl), cold-desert environment. These models are tested extensively and used globally to estimate PWV for low altitude sites (below 1000 m amsl). The moist parameters used in the model are: water vapor scale height (Hc), dew point temperature (Td) and water vapor pressure (Es0). These moist parameters are derived from surface air temperature and relative humidity measured at high temporal resolution from automated weather station. The performance of these models are examined statistically with observed high-resolution GPS (GPSPWV) data over the region (2005–2012). The correlation coefficient (R) between the observed GPSPWV and Model PWV is 0.98 at daily data and varies diurnally from 0.93 to 0.97. Parameterization of moisture parameters were studied in-depth (i.e., 2 h to monthly time scales) using GPSPWV, Td, and Es0. The slope of the linear relationships between GPSPWV and Td varies from 0.073°C−1 to 0.106°C−1 (R: 0.83 to 0.97) while GPSPWV and Es0 varied from 1.688 to 2.209 (R: 0.95 to 0.99) at daily, monthly and diurnal time scales. In addition, the moist parameters for the cold desert, high-altitude environment are examined in-depth at various time scales during 2005–2012.
Source: https://www.sciencedirect.com/science/article/pii/S1364682617305588?via%3Dihub
Structural insights from geodetic Global Positioning System measurements in the Darjiling-Sikkim Himalaya
by Malay Mukul, Sridevi Jade, Kutubuddin Ansari, Abdul Matin and Varun Joshi
Deformation in active convergent wedges like the Himalaya occurs over different time and space scales requiring integrated datasets for holistic insights into wedge-scale deformation. A new long-time series (1998–2009) of geodetic, static Global Positioning System (GPS) dataset suggests that active deformation in the Darjiling-Sikkim Himalaya (DSH) is not confined to the Himalayan front as previously believed. Instead, the ∼9 mm/yr N-S active convergence here is divided almost equally within the Lesser Himalayan Duplex (LHD) and the Higher Himalaya due to aseismic reverse slip of ∼18 mm/yr on the Himalayan décollement (Main Himalayan thrust (MHT)) dipping 6° → 006° and locked at ∼16 km depth. Slip transfer along the MHT causes minor to moderate earthquakes at the brittle-ductile transition in the DSH. Measured East velocities show no systematic variation indicating that strike-slip seismicity, though dominant in the region, does not alleviate the décollement (MHT) seismic hazard. Continued slip along the MHT, therefore, will cause a great décollement earthquake in the region. Also, GPS velocities vary in the eastern and western DSH suggesting segmentation of the Himalayan arc along a transverse fault over geological to decadal time scales. Our integrated approach can provide better insight into active deformation in convergent wedges worldwide.
Source: https://www.sciencedirect.com/science/article/pii/S0191814118301688?via%3Dihub
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