The Ladakh sector of the Himalaya is geologically significant as it preserves the imprints of the evolutionary history of the subduction-collision front between the Indian and the Eurasian plates in the Indian sector of the Himalayan arc. The region is also important for its geothermal potential. However, only a few geophysical studies have been conducted in Eastern Ladakh to delineate the underlying crustal/lithospheric structure and add the depth extent to surface tectonic features. We have taken up a magnetotelluric study in Eastern Ladakh to map its geoelectric crustal structure. Such a study shall also be helpful in assessing the geothermal potential as well as identification of deep reservoir(s), if any, present in this region. In this endeavor, we have covered a profile between Ukdungle and Fukche in eastern Ladakh.

Estimation of slip rate and hazard assessment in the Ladakh region

The NW-SE oriented Karakoram fault in the Ladakh region is the most prominent tectonic feature. It can be traced from Siachen region in the northwest to Nubra and Pangong region and further southeast of it. With a view to assess the seismic hazard through the estimation of slip rate on it, we installed 10 GPS sites across it in the Nubra and Pangong region. The results of continuous GPS measurements suggest that the fault in the Nubra valley is inactive while that in the Pangong region, slips at a rate of 1.6-3.2 mm/year. The low slip rate on the southern segment and no slip on the northern segment of the Karakoram fault support the model in which the Karakoram fault is considered a transient feature (and not a lithospheric scale fault) in the Himalayan arc deformation, that acted as transfer structure linking thrusts in the Pamir and western Tibet. Once the Longmu Co Gozha Co fault system (a part of the Altyn Tagh fault) developed in the late Pliocene and impinged on the Karakoram fault, the northern segment of the Karakoram fault became inactive. Further, our modelling of GPS measurements indicates a locking depth of ~12-15 km for the southern Karakoram fault. Although, because of low fault slip and uncertainty in the measurements it is not well constrained, the lack of historical and instrumental earthquakes of large magnitude implies that the southern part of the Karakoram fault has been accumulating deformation for several centuries, probably confirms that the southern Karakoram fault has been accumulating strain for several centuries while the fault in the Nubra region is inactive.

Using the 37 broadband seismographs in the Ladakh Himalaya region, the following aims are planned:

• The objective is to assess the necessary traits for Ladakh society to become mineral-rich, self-sufficient in geothermal energy, and earthquake-resistant. This goal can be attained by performing fundamental research and earthquake monitoring in various Ladakh regions.
• Quantifying earthquake hazard and crustal and mantle structural models relies on regularly updated earthquake catalogues, fault characterization, and source parameter identification.
• To better understand the geodynamics of the Ladakh Himalaya, we will study lateral changes in Moho depths, Lithospheric thicknesses, Mantle transition zone thickness, and upper mantle anisotropy using models. The deployment of ten strong-motion accelerographs in a CSIR-Mission mode project will provide insights into strong-motion parameters, site amplifications, and sediment thickness maps through research and earthquake monitoring.
• These strategies are essential for planning and developing earthquake-resistant structures that fulfil the specific needs of each micro-zone in Ladakh. The findings will help create more accurate town planning maps for Ladakh regions, as requested by stakeholders, including national and state disaster management authorities.
• Understanding the complex composition of Earth's crust and mantle, along with geology, can enhance understanding of potential geothermal energy resources and lithium reserves. This knowledge will improve geothermal energy and lithium exploration planning in Ladakh, benefiting the Union Territory government and other stakeholders.

Station location map of the Ladakh Himalayan region. Open brown triangles mark the location of Reftek broadband stations while open black triangles mark the location of Nanometric broadband stations. The solid black line represents major faults. ITSZ: Indus Tsangpo Suture Zone; STD: South Tibetan Detachment; KF: Karakoram Fault; BS: Bangong Suture; MCT: Main Central Thrust; MBT: Main Boundary Thrust; IGP: Indo-Gangetic Plain. SH, LH, HH and TH mark Siwalik Himalaya, Lesser Himalaya, Higher Himalaya, and Tethys Himalaya, respectively. TMD marks the location of the Tso-Morariri Dome.